Archives of Agronomy and Soil Science February 2006; 52(1): 79 – 103
Crop productivity and soil properties as affected by polyethylene film mulch and land configurations in groundnut (Arachis hypogaea L.) (Einfluss von Polyethylenfilm-Mulch und Feldbeschaffenheit auf Ertrag und Bodeneigenschaften im Erdnussanbau [Arachis hypogaea L.])
K. SUBRAHMANIYAN1,2, P. KALAISELVAN2, T. N. BALASUBRAMANIAN2, & WEIJUN ZHOU1 1
Department of Agronomy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China and 2Tamil Nadu Agricultural University, Vridhachalam, India
(Received 23 November 2004; accepted 11 October 2005)
Abstract Field experiments were conducted at Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India, during autumn 1999 and winter 2000 using groundnut to examine the effect of different colours of polyethylene film mulch on crop yield and soil properties. The results of the experiment conducted with different colours of polyethylene film mulch (black, transparent white and non-mulched control) and three land configurations (flat bed, ridges and furrows and broad bed and furrows) indicated that irrespective of the colours, polyethylene film mulch significantly increased the soil micro-organisms at all stages of observation during both seasons except for bacterial population, which was significantly higher under non-mulched control during the winter season. The soil physical properties such as rate of water loss/ day, soil bulk density, percentage of pore space and hydraulic conductivity were also favourably influenced by the polyethylene film mulch. The data on soil available nitrogen, phosphorus and potassium (NPK), showed that effect of polyethylene film mulch was significant at 30 DAS and not during later stages during both the seasons. Similarly the evolution of carbon dioxide (CO2) (soil respiration) was also significantly improved by polyethylene film mulch. The effect of land configuration was not significant for most of the parameters observed except for bulk density and pore space during winter seasons. With regard to yield parameters and yield, in both the seasons, white polyethylene film mulch out yielded other treatments in terms of groundnut pod yield. However the performance of white polyethylene film mulch was comparable with black polyethylene film mulch during winter 2001 – 2002 seasons. Among the land configurations, the results of yield components and yield were in favour of flat bed during both the seasons of study.
Keywords: Soil properties, polyethylene films, land configuration, groundnut
Correspondence: K. Subrahmaniyan, Department of Agronomy, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, 310029, China, and Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, 606001, India. E-mail:
[email protected] ISSN 0365-0340 print/ISSN 1476-3567 online Ó 2006 Taylor & Francis DOI: 10.1080/03650340500421786
80
K. Subrahmaniyan et al.
Introduction Crop production in semi-arid areas depends on rainfall and conservation of soil moisture is vital for grain production (Zhao et al. 1995). Mulching could reduce water evaporation and thereby increase the water availability to plants (Langdale et al. 1992). Plastic film mulching has long been used in agriculture. Plastic mulches directly affected the micro-climate around the plant by modifying the radiation budget of the surface and decreased the soil water loss. Determination of energy-radiating behaviour and its influence on the micro-climate around the plant was decided by the colour of the mulch used (Liakatas et al. 1986). Plastic film mulch increased the temperature gradients within the soil. This created an acceleration of water movement from deep to shallow levels within the soil, as soil moisture was constantly transported from hot to cold regions (Yi 1988). Lower bulk density and higher porosity of soil in the 0 – 7.5 and 7.5 – 15 cm layers under clear and black polyethylene film mulch in groundnut was ascribed to reduction of raindrop impact under polyethylene film mulch and consequent lower soil crust (Khan 1983). Plastic film mulch promoted early yields, did not immobilize N and increased nutrient availability by the way of reduced leaching (Bhella 1988). The highest uptake of N, P and K was observed in polyethylene-mulched plots. Increased uptake of N, P and K under mulch might be due to increased growth and yield characters (Vethamoni & Balakrishnan 1990). Earliness, soil moisture regulation, weed control, reduced fertilizer leaching, improved quality, reduced soil compaction, reduced root pruning and improved plant growth were the benefits from plastic mulch (Dean Mccraw & James 1999). Planting holes cut through plastic mulches potentially directed CO2 towards the canopy of seedlings, achieving the so-called ‘‘chimney effect’’. As much as 2x ambient CO2 concentration has been measured above holes cut for transplants (Soltani et al. 1995). Film mulching with varying specifications is currently used in northern China, covering about 7 million ha of field crops. Plastic film mulching has been used in cultivating groundnut (Arachis hypogaea), corn (Zea mays L.), cotton (Gossypium hirsutum L.), vegetables and fruit crops (Hu et al. 1995; Luo 1992; Zhang & Ma 1994; Han & Wan 1995). Plastic film inhibits soil water evaporation, resulting in an increase in water use, water use efficiency and dry matter production. Furthermore, it increases topsoil temperature and prolongs the reproductive growth period, which in turn enhances grain yield (Li et al. 1999). In recent years, plastic film mulch has also been adopted in dryland-farming ecosystems to further increase the grain yield. Most of these new techniques improve soil moisture or temperature. Increases in both soil moisture and temperature could increase grain yield over a short duration; but also disturb the original balance between abiotic and biotic factors in farming ecosystems and may have negative impact over sustainability (Feng-Min Li et al. 2004). With this background, this present study was planned to critically examine the impact of different colours of polyethylene film mulching on soil physical, chemical and biological properties and its effect on the pod yield of groundnut. Materials and methods Field experiments were conducted during autumn 2001 and winter 2001 – 2002 at the Regional Research Station, Tamil Nadu Agricultural University, Vridhachalam, India (118 300 N, 798 260 E, 42.67 m altitude). The experiment was conducted in Randomized Complete Block Design (RBD) with two factors viz. polyethylene film mulches (black, transparent, white and non-mulched control) and land configurations (broad beds and
Polyethylene mulch and land configurations in groundnut
81
furrows, ridges and furrows and flat bed). All treatments were replicated three times. The soil was a red sandy loam in texture with a pH of 7.3. For the initial soil available N, P and K was 217, 13.5 and 240 kg/ha and 220, 14.0 and 254 kg/ha respectively for autumn 2001 and winter 2001 – 2002 seasons. The initial bulk density of the soil was 1.450 and 1.420 g/cc during for autumn 2001 and winter 2001 – 2002 seasons respectively. During autumn 2001, the amount of rainfall during cropping season was 524.8 mm in 22 rainy days while during winter 2001 – 2002, 166.0 mm of rainfall was in three rainy days. During autumn 2001, the maximum temperature ranged from 32.6 – 37.98C while the minimum temperature ranged from 19.4 – 26.68C. During winter 2001 – 2002 season, the maximum and minimum temperatures ranged from 29.3 – 37.68C and 19.7 – 24.48C respectively. The plot size was 27 m2 (4.5 m 6 6.0 m). In experiment I, an area of 20 6 20 cm (2 seeds per hill) containing 33 plants/m2 was adopted for all treatments. In the broad bed furrow system of sowing, beds were formed at a dimension of 60 cm width, 15 cm in the furrows and slope on the either side of bed so that 5 beds of 27 m2 were formed per plot. Polyethylene sheets of 7-micron thickness with holes at the required spacing of 20 cm 6 20 cm were spread over the soil in the mulched plots and seeds sown. Similarly, ridges and furrows were formed at 90 cm apart and in a plot size of 4.5 m 6 6.0 m, five ridges and furrows were formed. Similar to broad bed and furrows and ridges and furrows, seeds were sown at a spacing of 20 6 20 cm (2 seeds per hill). A uniform fertilizer schedule of 17:35:54 kg N, P2O5 & K2O/ha was maintained for all the experiments and the entire quantity was applied at the time of sowing. The herbicide, Fluchloralin was applied at 2.0 litres/ha (1.0 kg ai/ha) to all treatments. No after-cultivation was done in the polyethylene film mulched plots, whereas one hand weeding on 30 days after sowing and earthing up on 45 days after sowing were done in the non-mulched plots. Soil samples were taken at 30 DAS to analyse the rate of CO2 evolution. The soils were analysed following the procedure suggested by Waksman and Starkey (1924). For soil microflora analysis, rhizosphere soil samples were taken from individual plots at 30, 60 DAS and at harvest. Soil water extract of respective treatment was cultured to assess soil microbial population. For assessing the fungal population, the extract was incubated at a concentration of 1073 in rose Bengal agar medium (Martin 1950) and the count was taken on the 4th day. For bacterial counts, the soil water extracts at a concentration of 1076 were inoculated in nutrient glucose agar medium (Allen 1953) and observed on the 3rd day. For actinomycetes, the soil water extract was inoculated in Kenknight’s agar medium (Allen 1953) at a concentration of 1073 and the count was taken on the 11th day. The undisturbed core samples were collected at harvest to monitor the changes in physical properties of soil. The bulk density, total pore space and saturated hydraulic conductivity of soil at 0 – 15 cm depth from the surface were measured by using core sampler (Gupta & Dakshinamurti 1980). Nutrient status of the soil (N, P2O5 and K2O) was also assessed using the soil samples collected at pre-sowing and 30 DAS. Available soil nitrogen, phosphorus and potassium were estimated following the procedure suggested by Subbiah and Asija (1956), Olsen et al. (1954) and Stanford and English (1949), respectively. The oven-dried plant samples used for dry matter estimation at harvest were chopped and ground in a Willey mill and were analysed for crop N, P and K uptake. Nitrogen content of the plant sample was estimated by the Micro-Kjeldahl method following the procedure given by Humphries (1956). Total phosphorus content was estimated from triple acid digestion extract using a photoelectric colorimeter with a blue filter as described by Jackson (1973). The amount of phosphorus content was determined by referring to a standard curve and the uptake calculated was expressed in kg/ha. Total potassium uptake in the plant sample was estimated from triple acid extract using a flame photometer (Jackson 1973). The nutrient values
82
K. Subrahmaniyan et al.
obtained as percentage in the analysis were calculated to kg/ha by multiplying with the corresponding whole plant dry matter obtained for each treatment. Soil moisture content of the soil at 15 cm layer depth was found out gravimetrically on a daily basis. Soils were collected in a moisture can and the wet weight of each sample was recorded. The soil sample was then dried in a hot air oven at 1058C until constant weight was obtained and dry weight of the sample was recorded (Gupta & Dakshinamurti 1980). From the moisture content obtained (on dry weight basis), the amount of water in the soil (depth) was calculated. From the daily data on the amount of water in the soil on depth basis, the rate of water loss (mm/day) was worked out for each treatment during both seasons. Since the samples were taken for only one replication, the data could not be analysed statistically. Analysis of Variance (ANOVA) was used to detect the significance of treatment effects on the different variables measured. Whenever the treatment means were significantly different, LSD was used to separate the mean. In general, differences are reported at 5% probability level.
Results Soil physical properties The mean data on rate of water loss (mm/day) is presented in Tables I and II. The rate of water loss/day was highest with non-mulched control. Irrespective of the treatments, the rate of water loss was higher between sowing to emergence phenophase of groundnut crop in both seasons. During both seasons, the effect of different mulch treatments on bulk density was significant. There was neither an increase or decrease in bulk density from the original values due to different colours of polyethylene film mulches evaluated. However, an increase in the bulk density from the original level was noticed in non-mulched control in both seasons. With regard to land configurations, the effect on bulk density was significant only during autumn 2001 and not during winter 2001 – 2002. The bulk density significantly increased from the original level of 1.450 – 1.472 g/cc in ridges and furrows followed by broad beds and furrows (1.467 g/cc). Flat bed exhibited the lowest bulk density among the three methods studied (1.427 g/cc). The mean data on pore space (%) of the experimental soils (Tables III and IV) revealed that the effect of mulch had a greater influence on the pore space of the soils in both the seasons. The amount of pore space was significantly higher in non-mulched control (22.52 and 24.73% respectively in autumn 2001 and winter 2001 – 2002 seasons) than polyethylene film mulched treatments in both the seasons. There was no significant difference among the different colours of polyethylene film mulch in both seasons though they were adjacent to the control. Land configurations exerted significant impact on pore space only during autumn 2001. Among the different land configurations, pore space was higher with flat bed (22.78%) than broad beds and furrows (20.49%) and ridges and furrows (20.15%). The effect of polyethylene film mulch on saturated hydraulic conductivity was significant in both seasons. Black and transparent polyethylene film mulch during autumn 2001 season and white polyethylene film mulch during winter 2001 – 2002 season had higher saturated hydraulic conductivity (10.53 and 10.52 respectively during autumn 2001 and winter 2001 – 2002 seasons) compared to nonmulched control, though no significant difference was observed between the different colours of polyethylene film mulch studied. Land configurations did not alter saturated hydraulic conductivity.
2.62 3.26 2.15 3.23 1.77 2.51 2.64
2.62
3.26
2.15 3.23 1.77 2.51
2.64
2.68
Mean
2.68
2.64
2.15 3.23 1.77 2.51
3.26
2.62
3.08 2.88
FB
2.68
2.64
2.15 3.23 1.77 2.51
3.26
2.62
3.09 2.88
Mean
2.46
2.21
1.98 2.08 1.74 2.35
3.09
2.63
3.43 2.67
BBF
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
2.69
3.10 2.89
3.08 2.88
Sowing – Emergence Emergence – Beginning bloom Beginning bloom – Beginning peg Beginning peg – Beginning pod Beginning pod – Full pod Full pod – Beginning seed Beginning seed – Full seed Full seed – Beginning maturity Beginning maturity – Harvest
RF
BBF
Growth stages
Black
2.47
2.21
1.98 2.08 1.74 2.35
3.10
2.63
3.43 2.67
RF
2.46
2.21
1.98 2.08 1.74 2.35
3.09
2.63
3.43 2.67
FB
Transparent
2.46
2.21
1.98 2.08 1.74 2.35
3.09
2.63
3.43 2.67
Mean
2.68
2.55
1.97 2.87 2.18 2.51
3.24
2.76
3.48 2.55
BBF
2.68
2.55
1.97 2.87 2.18 2.51
3.24
2.76
3.48 2.55
RF
2.68
2.55
1.97 2.87 2.18 2.51
3.24
2.76
3.48 2.55
FB
White
2.68
2.55
1.97 2.87 2.18 2.51
3.24
2.76
3.48 2.55
Mean
3.97
3.02
4.28 3.74 2.31 3.65
3.84
3.87
6.77 4.27
BBF
3.97
3.02
4.28 3.74 2.31 3.65
3.84
3.87
6.77 4.28
RF
3.97
3.02
4.28 3.74 2.31 3.65
3.84
3.87
6.77 4.27
FB
Control
3.97
3.02
4.28 3.74 2.31 3.65
3.84
3.87
6.77 4.27
Mean
Table I. Effect of polyethylene film mulches and land configurations on rate of water loss (mm/day) including ET and infiltration during different phenophases of groundnut (Based on soil moisture values 0 – 15 cm) during autumn 2001 season.
Polyethylene mulch and land configurations in groundnut 83
2.42 1.54 1.58 1.51 1.30 1.66 2.16
2.42
1.54
1.58 1.51 1.30 1.66
2.15
2.00
Mean
2.00
2.15
1.58 1.51 1.30 1.66
1.54
2.43
3.66 2.18
RF
2.00
2.15
1.58 1.51 1.30 1.66
1.54
2.42
3.66 2.18
Mean
2.01
2.34
1.47 1.74 1.20 1.78
1.66
2.02
3.52 2.39
BBF
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
2.00
3.66 2.18
3.66 2.18
Sowing – Emergence Emergence – Beginning bloom Beginning bloom – Beginning peg Beginning peg – Beginning pod Beginning pod – Full pod Full pod – Beginning seed Beginning seed – Full seed Full seed – Beginning maturity Beginning maturity – Harvest
FB
BBF
Growth stages
Black
2.01
2.34
1.47 1.74 1.20 1.78
1.66
2.02
3.52 2.39
FB
2.01
2.35
1.47 1.74 1.20 1.78
1.66
2.03
3.52 2.39
RF
Transparent
2.01
2.34
1.47 1.74 1.20 1.78
1.66
2.02
3.52 2.39
Mean
1.95
2.36
1.39 1.15 1.51 1.61
1.77
1.88
3.66 2.25
BBF
1.96
2.37
1.39 1.15 1.51 1.61
1.77
1.88
3.67 2.25
FB
1.95
2.36
1.39 1.15 1.51 1.61
1.77
1.88
3.66 2.25
RF
White
1.95
2.36
1.39 1.15 1.51 1.61
1.77
1.88
3.66 2.25
Mean
2.32
2.47
2.03 2.11 2.02 1.81
2.22
2.05
4.25 1.97
BBF
2.32
2.47
2.03 2.11 2.02 1.82
2.22
2.05
4.25 1.97
FB
2.33
2.47
2.03 2.11 2.03 1.81
2.23
2.05
4.25 1.97
RF
Control
2.32
2.47
2.03 2.11 2.02 1.81
2.22
2.05
4.25 1.97
Mean
Table II. Effect of polyethylene film mulches and land configurations on rate of water loss (mm/day) including ET and infiltration during different phenophases of groundnut (Based on soil moisture values 0 – 15 cm) during winter season 2001 – 2002.
84 K. Subrahmaniyan et al.
1.467
Mean
1.472
1.436 1.432 1.434 1.518
Mean
0.008 0.007 0.014
LSD ( p ¼ 0.05)
1.427
1.40 1.40 1.40 1.52
FB
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
0.004 0.003 0.007
RF
1.46 1.45 1.46 1.52
SEm+
1.45 1.45 1.45 1.52
Black Transparent White Control
PE films LC PE X LC
BBF
Polyethylene films
Bulk density (g/cc)
0.253 0.219 0.439
RF
20.15
19.37 19.56 19.37 22.32
SEm+
20.49
19.56 19.93 19.74 22.75
BBF 20.64 20.72 20.70 22.52
Mean
0.525 0.455 0.909
LSD ( p ¼ 0.05)
22.78
22.98 22.69 22.98 22.49
FB
Pore space (%)
0.013 0.011 0.023
RF
10.46
10.52 10.53 10.51 10.29
SEm+
10.47
10.54 10.53 10.53 10.29
BBF
10.53 10.53 10.52 10.29
Mean
0.027 NS NS
LSD ( p ¼ 0.05)
10.47
10.52 10.53 10.52 10.30
FB
Hydraulic conductivity (m/s 6 107)
Table III. Effect of polyethylene film mulches and land configurations on bulk density (g/cc), percentage of pore space (%) and hydraulic conductivity (m/s 6 107) at harvest during autumn season 2001.
Polyethylene mulch and land configurations in groundnut 85
1.418
Mean
1.417
1.397 1.397 1.398 1.474
Mean
0.012 NS NS
LSD ( p ¼ 0.05)
1.414
1.40 1.40 1.40 1.47
FB
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
0.006 0.005 0.010
RF
1.40 1.40 1.40 1.48
SEm+
1.40 1.40 1.40 1.48
Black Transparent White Control
PE films LC PE X LC
BBF
Polyethylene films
Bulk density (g/cc)
0.335 0.290 0.580
RF
23.15
22.69 22.69 22.69 24.53
SEm+
23.13
22.69 22.69 22.51 24.62
BBF 22.79 22.69 22.73 24.73
Mean
0.694 NS NS
LSD ( p ¼ 0.05)
23.42
22.98 22.69 22.98 25.04
FB
Pore space (%)
0.012 0.010 0.021
RF
10.46
10.52 10.52 10.51 10.29
SEm+
10.47
10.53 10.52 10.53 10.28
BBF
10.51 10.51 10.52 10.29
Mean
0.025 NS NS
LSD ( p ¼ 0.05)
10.45
10.49 10.49 10.51 10.30
FB
Hydraulic conductivity (m/s 6 107)
Table IV. Effect of polyethylene film mulches and land configurations on bulk density (g/cc), percentage of pore space (%) and hydraulic conductivity (m/s 6 107) at harvest during winter season 2001 – 2002.
86 K. Subrahmaniyan et al.
Polyethylene mulch and land configurations in groundnut
87
Soil chemical properties Soil available nutrients. Polyethylene film mulch exerted a great influence on available soil nitrogen, soil available phosphorus and soil available potassium (see Table V) at 30 DAS in both the seasons. During autumn season 2001, the available soil nitrogen and potassium were higher with black polyethylene film mulch compared to the non-mulched control. This was on a par with the other two colours of polyethylene film mulch. The same trend was noted for winter season 2001 – 2002. With regard to available phosphorus, white polyethylene film mulch left higher P though it was on a par with transparent and black polyethylene film mulch during both seasons. Land configuration did not influence soil available nitrogen, phosphorus and potassium during both seasons. Soil biological properties Microbial population dynamics. The mean data on bacterial population (see Tables VI and VII), revealing the effect of polyethylene film mulches on bacterial population, was significant only during autumn 2001. Transparent polyethylene film mulch registered higher bacterial populations at all three stages of observation viz., 30 DAS, 60 DAS and at harvest. In contrast to autumn season 2001 observations, non-mulched control had significantly higher bacterial population at all the three stages of winter 2001 – 2002 season. Land configurations and interaction effects did not affect this parameter. The effect of polyethylene film mulches on fungal population was significant in both seasons (see Tables VIII and IX). The fungal population was higher in black polyethylene film mulch at all three stages during autumn season 2001, while transparent polyethylene film mulch had a significantly higher population of fungi during winter 2001 – 2002 season. Land configurations methods did not influence the parameters. The perusal of mean data on actinomycetes population (see Tables X and XI) revealed that polyethylene film mulch exerted significant influences on actinomycetes population at all three stages in both seasons. Among the different mulch treatments studied, transparent polyethylene film mulch had enhanced actinomycetes population during both the seasons. Similar to bacterial and fungal population, there was no significant influence from land configurations on actinomycetes population. Rate of CO2 evolution (mg/100 g of soil) The CO2 evolution rate did not differ markedly between the two seasons (see Table XII). Polyethylene film mulch exerted a significant influence on CO2 evolution rate during both seasons. Among the different mulches tested, the CO2 evolution rate was higher with transparent polyethylene film mulch (13.91 and 14.06 mg/100 g of soil respectively during autumn and winter seasons) than with non-mulched control (12.79 and 13.18 mg/100 g of soil, which was on a par with white and black polyethylene film mulches. Land configurations did not influence CO2 evolution rate significantly in both seasons. Crop nutrient uptake Polyethylene film mulches significantly altered N, P and K uptake of groundnut in both autumn and winter (see Table XIII). N, P and K uptake were higher with white polyethylene film mulch during both seasons. However during winter season 2001 – 2002, the N, P and K uptake observed with white polyethylene film mulch was comparable with black polyethylene
212
212
208
173
201
Black
Transparent
White
Control
Mean
195
159
206
208
208
RF
LC
168
208
211
211
Mean
NS
NS
LSD ( p ¼ 0.05) 14.082
202
173
209
213
214
FB
199
162
210
212
213
RF
24.646
12.323
14.229
SEm+
205
176
212
216
216
BBF
173
213
217
218
Mean
NS
NS
LSD ( p ¼ 0.05) 29.508
212
180
218
224
224
FB
Winter 2001 – 2002
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
PE X LC
6.791
5.881 11.762
PE films
SEm+
BBF
Polyethylene films
Autumn 2001
Soil available N (kg/ha)
27
21
28
28
29
RF
3.614
1.807
2.086
SEm+
26
21
29
29
27
BBF
21
30
29
29
Mean
NS NS
LSD ( p ¼ 0.05) 4.327
29
21
32
30
30
FB
Autumn 2001
27
21
28
28
30
RF
3.718
1.859
2.147
SEm+
27
21
29
29
28
BBF
21
30
29
29
Mean
NS
NS
LSD ( p ¼ 0.05) 4.452
29
22
33
31
30
FB
Winter 2001 – 2002
Soil available P (kg/ha)
230
193
239
241
247
RF
30.671
15.336
17.708
SEm+
229
197
240
237
243
BBF
196
240
238
245
Mean
NS
NS
LSD ( p ¼ 0.05) 36.723
230
198
241
235
245
FB
Autumn 2001
235
198
246
247
249
RF
29.934
14.967
17.283
SEm+
235
205
246
241
250
BBF
203
246
243
250
Mean
NS
NS
LSD ( p ¼ 0.05) 35.841
236
206
246
240
251
FB
Winter 2001 – 2002
Soil available K (kg/ha)
Table V. Effect of polyethylene film mulches and land configurations on soil available N, P and K at 30 DAS during autumn 2001 and winter 2001 – 2002 seasons.
88 K. Subrahmaniyan et al.
36.67 (7.563) 45.67 (7.659) 35.00 (7.544) 25.33 (7.403)
Mean
LSD ( p ¼ 0.05) 0.024 NS NS
34.00 (7.525)
36.25 (7.551)
FB 33 (7.519) 43 (7.633) 33 (7.519) 27 (7.431)
RF
37 (7.568) 45 (7.653) 37 (7.568) 26 (7.415)
SEm+ 0.011 0.010 0.020
36.75 (7.550)
40 (7.602) 49 (7.690) 35 (7.544) 23 (7.362)
BBF
*Figures in the parenthesis are logarithmic transformed values.
PE films LC PE X LC
Mean
Control
White
Transparent
Black
Polyethylene films
30 DAS RF
50.0 (7.673)
54 (7.732) 64 (7.806) 57 (7.756) 25 (7.398)
SEm+ 0.008 0.007 0.015
55.5 (7.725)
62 (7.792) 68 (7.833) 61 (7.785) 31 (7.491)
BBF
FB 57.33 (7.758) 65.67 (7.817) 57.67 (7.761) 28.00 (7.445)
Mean
LSD ( p ¼ 0.05) 0.017 NS NS
51.0 (7.687)
56 (7.748) 65 (7.813) 55 (7.740) 28 (7.447)
60 DAS RF
61.00 (7.759)
65 (7.813) 83 (7.919) 65 (7.813) 31 (7.491)
SEm+ 0.005 0.004 0.008
63.25 (7.770)
67 (7.826) 87 (7.940) 69 (7.839) 30 (7.477)
BBF
FB
64.00 (7.806) 83.67 (7.922) 66.67 (7.824) 31.00 (7.491)
Mean
LSD ( p ¼ 0.05) 0.009 NS NS
59.75 (7.753)
60 (7.778) 81 (7.908) 66 (7.820) 32 (7.505)
Harvest
Table VI. Effect of polyethylene film mulches and land configurations on bacteria population (6106 cfu/g) at 30, 60 DAS and at harvest during autumn 2001 season.
Polyethylene mulch and land configurations in groundnut 89
PE films LC PE X LC
Mean
Control
White
Transparent
Black
Polyethylene films
0.014 0.012 0.024
43.44 (7.638) 35.11 (7.545) 42.33 (7.626) 52.00 (7.716)
Mean
0.029 NS NS
LSD ( p ¼ 0.05)
44.00 (7.640)
43.00 (7.629)
FB 42 (7.623) 37 (7.568) 44 (7.643) 53 (7.724)
RF
43 (7.633) 34 (7.531) 43 (7.633) 52 (7.716)
SEm+
42.67 (7.625)
45 (7.656) 34 (7.536) 40 (7.602) 51 (7.708)
BBF
30 DAS RF
54.75 (7.737)
57 (7.756) 50 (7.699) 53 (7.724) 59 (7.771)
0.007 0.006 0.012
SEm+
53.75 (7.730)
56 (7.748) 49 (7.690) 52 (7.719) 58 (7.761)
BBF
FB 57.00 (7.756) 50.00 (7.699) 53.11 (7.725) 58.89 (7.770)
Mean
0.014 NS NS
LSD ( p ¼ 0.05)
55.75 (7.745)
58 (7.763) 51 (7.708) 54 (7.732) 60 (7.778)
60 DAS RF
59.75 (7.775)
63 (7.799) 52 (7.716) 58 (7.763) 66 (7.820)
0.008 0.007 0.013
SEm+
60.25 (7.777)
64 (7.806) 50 (7.699) 60 (7.778) 67 (7.826)
BBF
FB
63.00 (7.799) 51.00 (7.708) 58.00 (7.763) 67.33 (7.828)
Mean
0.016 NS NS
LSD ( p ¼ 0.05)
59.50 (7.772)
62 (7.792) 51 (7.708) 56 (7.748) 69 (7.839)
Harvest
Table VII. Effect of polyethylene film mulches and land configurations on bacteria population (6106 cfu/g) at 30, 60 DAS and at harvest during winter 2001 – 2002 season.
90 K. Subrahmaniyan et al.
63.33 (4.801) 55.33 (4.741) 58.67 (4.767) 55.67 (4.718)
Mean
LSD ( p ¼ 0.05) 0.021 NS NS
57.00 (4.734)
56.50 (4.751)
FB 62 (4.792) 51 (4.707) 57 (4.755) 58 (4.681)
RF
63 (4.799) 54 (4.732) 55 (4.740) 54 (4.732)
SEm+ 0.010 0.009 0.007
61.25 (4.785)
65 (4.812) 61 (4.783) 64 (4.806) 55 (4.740)
BBF
*Figures in the parenthesis are logarithmic transformed values.
PE films LC PE X LC
Mean
Control
White
Transparent
Black
Polyethylene films
30 DAS RF
62.50 (4.794)
70 (4.845) 57 (4.756) 63 (4.799) 60 (4.778)
SEm+ 0.010 0.009 0.007
65.00 (4.812)
69 (4.839) 64 (4.808) 69 (4.836) 58 (4.763)
BBF
FB 68.00 (4.832) 58.33 (4.765) 64.00 (4.804) 57.00 (4.755)
Mean
LSD ( p ¼ 0.05) 0.021 NS NS
58.00 (4.761)
65 (4.813) 54 (4.731) 60 (4.778) 53 (4.723)
60 DAS RF
68.50 (4.833)
80 (4.903) 60 (4.778) 70 (4.845) 64 (4.806)
SEm+ 0.008 0.007 0.014
71.00 (4.849)
78 (4.892) 69 (4.836) 75 (4.875) 62 (4.792)
BBF
FB
75.33 (4.876) 61.33 (4.785) 69.67 (4.842) 61.00 (4.785)
Mean
LSD ( p ¼ 0.05) 0.017 NS NS
61.00 (4.783)
68 (4.832) 55 (4.740) 64 (4.806) 57 (4.756)
Harvest
Table VIII. Effect of polyethylene film mulches and land configurations on fungi population (6103 cfu/g) at 30, 60 DAS and at harvest during autumn 2001 season.
Polyethylene mulch and land configurations in groundnut 91
0.005 0.005 0.009
370.44 (5.569) 392.56 (5.594) 384.33 (5.585) 366.11 (5.564)
Mean
0.011 NS NS
LSD ( p ¼ 0.05)
377.00 (5.576)
377.25 (5.576)
FB 370 (5.568) 391 (5.592) 380 (5.580) 367 (5.565)
RF
369 (5.567) 392 (5.593) 385 (5.585) 363 (5.560)
SEm+
380.83 (5.581)
372 (5.571) 395 (5.596) 388 (5.589) 368 (5.566)
BBF
*Figures in the parenthesis are logarithmic transformed values.
PE films LC PE X LC
Mean
Control
White
Transparent
Black
Polyethylene films
30 DAS RF
397.00 (5.598)
388 (5.588) 410 (5.613) 405 (5.607) 385 (5.585)
0.007 0.006 0.012
SEm+
398.75 (5.600)
391 (5.592) 412 (5.615) 408 (5.610) 384 (5.584)
BBF
FB 389.56 (5.590) 410.44 (5.613) 406.33 (5.609) 383.67 (5.584)
Mean
0.014 NS NS
LSD ( p ¼ 0.05)
396.75 (5.598)
390 (5.591) 409 (5.612) 406 (5.608) 382 (5.582)
60 DAS RF
388.00 (5.589)
383 (5.583) 400 (5.602) 395 (5.597) 374 (5.573)
0.006 0.005 0.010
SEm+
389.42 (5.590)
384 (5.584) 401 (5.603) 393 (5.595) 380 (5.579)
BBF
FB
382.22 (5.582) 401.00 (5.603) 392.78 (5.594) 376.22 (5.575)
Mean
0.012 NS NS
LSD ( p ¼ 0.05)
386.75 (5.587)
380 (5.580) 402 (5.604) 390 (5.591) 375 (5.574)
Harvest
Table IX. Effect of polyethylene film mulches and land configurations on fungi population (6103 cfu/g) at 30, 60 DAS and at harvest during winter 2001 – 2002 season.
92 K. Subrahmaniyan et al.
0.010 0.009 0.007
63.33 (4.801) 55.33 (4.741) 58.67 (4.767) 55.67 (4.718)
Mean
0.021 NS NS
LSD ( p ¼ 0.05)
57.00 (4.734)
56.50 (4.751)
FB 62 (4.792) 51 (4.707) 57 (4.755) 58 (4.681)
RF
63 (4.799) 54 (4.732) 55 (4.740) 54 (4.732)
SEm+
61.25 (4.785)
65 (4.812) 61 (4.783) 64 (4.806) 55 (4.740)
BBF
*Figures in the parenthesis are logarithmic transformed values.
PE films LC PE X LC
Mean
Control
White
Transparent
Black
Polyethylene films
30 DAS RF
62.50 (4.794)
70 (4.845) 57 (4.756) 63 (4.799) 60 (4.778)
0.010 0.009 0.007
SEm+
65.00 (4.812)
69 (4.839) 64 (4.808) 69 (4.836) 58 (4.763)
BBF
FB 68.00 (4.832) 58.33 (4.765) 64.00 (4.804) 57.00 (4.755)
Mean
0.021 NS NS
LSD ( p ¼ 0.05)
58.00 (4.761)
65 (4.813) 54 (4.731) 60 (4.778) 53 (4.723)
60 DAS RF
68.50 (4.833)
80 (4.903) 60 (4.778) 70 (4.845) 64 (4.806)
0.008 0.007 0.014
SEm+
71.00 (4.849)
78 (4.892) 69 (4.836) 75 (4.875) 62 (4.792)
BBF
FB
75.33 (4.876) 61.33 (4.785) 69.67 (4.842) 61.00 (4.785)
Mean
0.017 NS NS
LSD ( p ¼ 0.05)
61.00 (4.783)
68 (4.832) 55 (4.740) 64 (4.806) 57 (4.756)
Harvest
Table X. Effect of polyethylene film mulches and land configurations on actinomycetes population (6103 cfu/g) at 30, 60 DAS and at harvest during autumn 2001 season.
Polyethylene mulch and land configurations in groundnut 93
0.010 0.009 0.007
63.33 (4.801) 55.33 (4.741) 58.67 (4.767) 55.67 (4.718)
Mean
0.021 NS NS
LSD ( p ¼ 0.05)
57.00 (4.734)
56.50 (4.751)
FB 62 (4.792) 51 (4.707) 57 (4.755) 58 (4.681)
RF
63 (4.799) 54 (4.732) 55 (4.740) 54 (4.732)
SEm+
61.25 (4.785)
65 (4.812) 61 (4.783) 64 (4.806) 55 (4.740)
BBF
*Figures in the parenthesis are logarithmic transformed values.
PE films LC PE X LC
Mean
Control
White
Transparent
Black
Polyethylene films
30 DAS RF
62.50 (4.794)
70 (4.845) 57 (4.756) 63 (4.799) 60 (4.778)
0.010 0.009 0.007
SEm+
65.00 (4.812)
69 (4.839) 64 (4.808) 69 (4.836) 58 (4.763)
BBF
FB 68.00 (4.832) 58.33 (4.765) 64.00 (4.804) 57.00 (4.755)
Mean
0.021 NS NS
LSD ( p ¼ 0.05)
58.00 (4.761)
65 (4.813) 54 (4.731) 60 (4.778) 53 (4.723)
60 DAS RF
68.50 (4.833)
80 (4.903) 60 (4.778) 70 (4.845) 64 (4.806)
0.008 0.007 0.014
SEm+
71.00 (4.849)
78 (4.892) 69 (4.836) 75 (4.875) 62 (4.792)
BBF
FB
75.33 (4.876) 61.33 (4.785) 69.67 (4.842) 61.00 (4.785)
Mean
0.017 NS NS
LSD ( p ¼ 0.05)
61.00 (4.783)
68 (4.832) 55 (4.740) 64 (4.806) 57 (4.756)
Harvest
Table XI. Effect of polyethylene film mulches and land configurations on actinomycetes population (6103 cfu/g) at 30, 60 DAS and at harvest during winter 2001 – 2002 season.
94 K. Subrahmaniyan et al.
13.82 14.17 13.17 12.97
13.53
Black Transparent White Control
Mean
0.189 0.164 0.328
SEm+
13.45
13.13 13.77 13.93 12.97
RF
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
PE films LC PE X LC
BBF
Polyethylene films 13.45 13.91 13.69 12.79
Mean
0.392 NS NS
LSD ( p ¼ 0.05)
13.40
13.40 13.80 13.97 12.45
FB
Autumn 2001
13.85
13.97 14.07 14.21 13.17
BBF
0.152 0.132 0.264
SEm+
13.75
13.97 13.93 13.95 13.15
RF
13.84 13.96 14.06 13.18
Mean
0.316 NS NS
LSD ( p ¼ 0.05)
13.69
13.60 13.88 14.03 13.23
FB
Winter 2001 – 2002
Table XII. Effect of polyethylene film mulches and land configurations on rate of CO2 evolution (mg/100 g of soil) during autumn 2001 and winter 2001 – 2002 season.
Polyethylene mulch and land configurations in groundnut 95
161
Mean
150
154 157 176 115
2.892 2.504 5.009
163 171 188 122
Mean
LSD (p ¼ 0.05) 5.997 5.194 NS
172
172 181 200 134
FB
169
181 173 182 139
RF
4.323 3.744 7.488
SEm+
165
175 176 178 132
BBF 180 171 183 139
Mean
LSD (p ¼ 0.05) 8.966 7.764 NS
171
185 163 189 146
FB
Winter 2001 – 2002
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
PE films LC PE X LC
162 177 189 116
Black Transparent White Control
RF
SEm+
BBF
Polyethylene films
Autumn 2001
N uptake (kg/ha)
35
40 35 41 25
RF
0.887 0.768 1.536
SEm+
35
33 36 41 29
BBF 37 37 40 27
Mean
LSD (p ¼ 0.05) 1.839 NS NS
35
38 39 38 27
FB
Autumn 2001
35
41 34 39 28
RF
0.883 0.765 1.530
SEm+
33
33 35 37 29
BBF 38 34 37 28
Mean
LSD (p ¼ 0.05) 1.832 NS NS
34
40 34 34 28
FB
Winter 2001 – 2002
P uptake (kg/ha)
214
228 221 248 160
RF
5.656 4.898 9.796
SEm+
230
242 230 271 176
BBF
236 234 263 168
Mean
LSD (p ¼ 0.05) 11.729 10.158 NS
231
237 252 269 167
FB
Autumn 2001
211
223 221 234 165
RF
5.389 4.667 9.333
SEm+
212
235 214 235 163
BBF
226 216 233 164
Mean
LSD (p ¼ 0.05) 11.175 NS NS
206
220 212 230 163
FB
Winter 2001 – 2002
K uptake (kg/ha)
Table XIII. Effect of polyethylene film mulches and land configurations on crop N, P and K uptake at harvest during autumn 2001 and winter 2001 – 2002 seasons.
96 K. Subrahmaniyan et al.
Polyethylene mulch and land configurations in groundnut
97
film mulch. Land configurations did not improve N, P and K uptake significantly during both seasons. Yield attributes and yield of groundnut The data on the yield components (see Tables XIV and XV) revealed that the difference in matured pods per plant between polyethylene film mulches was significant in both seasons. White polyethylene film mulch had a higher number of matured pods per plant (24.38 and 21.53 respectively in autumn 2001 and winter 2001 – 2002) in both the seasons. However, it was on a par with black polyethylene film mulch (20.56) during winter 2001 – 2002 season. Land configurations did not have any profound influence on the number of matured pods per plant in both seasons. A significant increase in 100 seed weight was observed with polyethylene film mulches. The influence of land configurations on 100 seed weight and shelling percentage was significant only during winter 2001 – 2002, while shelling percentage was significant only during winter season 2001 – 2002. Similar to 100 seed weight, shelling percentage was also significantly altered by land configurations during the winter 2001 – 2002 season. Among the different treatments, white polyethylene film mulch registered a significantly higher pod yield (2399 kg/ha) than the non-mulched control (1270 kg/ha) during autumn 2001 season. During winter 2001 – 2002, although higher pod yield was obtained from white polyethylene film mulch, the groundnut yield obtained under black polyethylene film mulch was on a par. In both the seasons, control treatment recorded the lowest yield significantly. Flat bed registered a significantly higher pod yield (2229 and 2681 kg/ha respectively in autumn 2001 and winter 2001 – 2002 seasons) compared to other land configurations.
Discussion Soil physical properties Improvement of the water use efficiency by better utilization of soil water appears to be the best way to increase grain yield in the semi-arid areas (Zhao et al. 1995). The principle ways of increasing water use efficiency include reducing soil water evaporation and exploiting deep soil water, in order to support shoot biomass accumulation and optimize the dry matter allocation by selectively increasing the reproduction (Li et al. 1997, 2000; Li & Zhao 1995). Polyethylene film mulch prevented soil water evaporation and thus helped in retaining soil moisture in groundnut. Hu et al. (1995) observed that water vapour flux density in the top 20 cm of soil with polyethylene film mulch was 1.7 times higher than the control. This indicated the upward movement of water from the deeper layers. In the present study, the rate of water loss was lower with polyethylene film mulch than the non-mulched control. Shaikh et al. (2002) also observed that polyethylene film mulch in groundnut gave maximum water use efficiency of 5.12 kg/ha mm compared to straw mulch (2.95 kg/ha mm) and control (2.51 kg/ha mm), which resulted in 78.7% increased pod yield compared to the control. Similarly Raskar and Bhoi (2002) reported maximum water use efficiency of 5.96 kg/ha mm under plastic film mulch compared to control (3.49 kg/ha mm) in groundnut. There was not much difference among the different colours of polyethylene film mulches with respect to the rate of water loss. Since there was no variation in colours of polyethylene film mulch in preventing soil water evaporation, the rate of water loss did not differ. A similar trend of results was reported by Chakraborty and Sadhu (1994) who reported that different colours of polyethylene mulches, viz. transparent, black, white, green and red resulted in greater soil
20.27
Mean
19.82
20.7 20.2 24.9 13.5
1.713 1.483 2.967
20.73 20.58 24.38 13.76
Mean
3.552 NS NS
LSD (p ¼ 0.05)
19.50
20.8 21.0 22.5 13.7
FB
40.71
38.52 38.66 44.15 41.50
RF
0.78 0.67 1.35
SEm+
40.38
39.50 39.42 43.24 39.35
BBF 39.17 39.41 43.52 40.51
Mean
1.61 NS NS
LSD (p ¼ 0.05)
40.87
39.50 40.14 43.18 40.68
FB
100 seed weight (g)
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
PE films LC PE X LC
20.7 20.5 25.8 14.1
Black Transparent White Control
RF
SEm+
BBF
Polyethylene films
Number of matured pods/plant
67.3
66.5 66.8 68.2 68.0
RF
0.55 0.87 0.98
SEm+
67.7
67.6 67.6 68.9 66.7
BBF
67.2 67.1 68.7 67.5
Mean
NS NS NS
LSD (p ¼ 0.05)
67.9
67.6 66.9 69.0 67.9
FB
Shelling (%)
1638
1456 1884 2098 1114
RF
102.87 89.09 178.18
SEm+
1825
1788 2063 2437 1014
BBF
1801 2120 2399 1270
Mean
213.35 184.77 NS
LSD (p ¼ 0.05)
2229
2158 2414 2662 1681
FB
Pod yield (kg/ha)
Table XIV. Effect of polyethylene film mulches and land configurations on yield attributes and pod yield of groundnut during autumn 2001 season.
98 K. Subrahmaniyan et al.
18.42
Mean
19.65
23.0 17.9 22.7 14.9
1.06 0.92 1.84
20.56 17.76 21.53 14.64
Mean
2.20 NS NS
LSD (p ¼ 0.05)
17.80
19.3 16.5 20.0 15.3
FB
42.14
41.32 43.39 43.31 40.54
RF
0.70 0.61 1.22
SEm+
43.36
43.18 44.50 43.67 42.10
BBF 42.90 44.85 44.05 41.40
Mean
1.47 1.27 NS
LSD (p ¼ 0.05)
44.39
44.22 46.64 45.15 41.57
FB
100 seed weight (g)
BBF, Broad bed and furrows; RF, Ridges and furrows; FB, Flat bed.
PE films LC PE X LC
19.3 18.8 21.9 13.7
Black Transparent White Control
RF
SEm+
BBF
Polyethylene films
Number of matured pods/plant
72.4
72.2 73.2 73.2 71.0
RF
0.56 0.48 0.97
SEm+
73.6
73.6 74.4 74.2 72.0
BBF
72.4 73.8 73.3 71.3
Mean
1.16 1.00 NS
LSD (p ¼ 0.05)
72.1
71.3 73.7 72.6 70.9
FB
Shelling (%)
2494
2677 2490 2630 2179
RF
46.72 40.46 80.92
SEm+
2435
2474 2397 2661 2207
BBF
2677 2531 2723 2214
Mean
96.88 83.90 NS
LSD (p ¼ 0.05)
2681
2879 2708 2879 2256
FB
Pod yield (kg/ha)
Table XV. Effect of polyethylene film mulches and land configurations on yield attributes and pod yield of groundnut during winter 2001 – 2002 season.
Polyethylene mulch and land configurations in groundnut 99
100
K. Subrahmaniyan et al.
moisture conservation when compared to the control. The rate of water loss was at a maximum during the autumn season when compared to winter. This was obviously due to higher temperature and lower humidity prevailed during that period. Since the soil was not disturbed from sowing to harvest under mulched plots, the bulk density of the soil was not altered. The improved micro-climate conditions maintained under mulched plot would have also avoided soil crusting and maintained the soil bulk density throughout the crop period. However, soil disturbance in the non-mulched plots due to weeding and earthing up operations, might have increased the bulk density. In addition the rainwater impact and run-off would have resulted in soil crusting under non-mulched control, which is a common phenomenon in red sandy soil. The favourable soil structure under polyethylene film mulch was also reflected on the hydraulic conductivity and the pore space. Similarly, Hu et al. (1995) reported that the bulk density of soil at harvest from the top 50 cm layer under polyethylene film mulched groundnut was noted to be 1.30 – 1.44 g/cc which was 0.11 – 0.20 g/cc less than the control. The total porosity increased by 3.0 – 5.2%, capillary porosity by 1.7 – 7.6% and aeration porosity by 0.4 – 3.5% over the control. Soil chemical properties Soil available nutrients. Fertilizer applied under polyethylene film mulch was not lost by leaching, so that fertilizers were optimally used and not wasted. In addition, the soil under plastic mulch remained loose, friable and well aerated. Hence roots had adequate oxygen and microbial activity was enhanced (Lamont 1991). In the present study, the available N, P and K was significantly higher but only during early stages (30 DAS) of the crop under polyethylene film mulch. This may be explained by the arrest of leaching and volatilization losses of applied fertilizers under polyethylene film mulches, since all the fertilizers were applied as basal in groundnut. However the effect of mulch on available N, P and K was not significant in the later stages of crop (data not given), which might be due to higher crop N, P and K uptake. Soil biological properties In general, mulching resulted in an increased soil microbial population during both growing seasons except bacterial population during winter seasons. Soil moisture conditions play an important role in the changes of soil microbial population in semi-arid areas. Studies by Smith et al. (1993) have shown that a significant correlation existed between soil moisture level and micro-organisms and also there was a close relationship between mineralized N and microbial biomass N. In the present study, better soil moisture maintained under plastic mulch might have resulted in greater soil microflora during autumn seasons. Due to the prevalence of the favourable temperature and humidity during the winter season, the effect of mulch might not have been noticeable. Hence the bacterial population was less in mulched plots as compared to control. Similarly, Hu et al. (1995) reported that polyethylene film mulch significantly increased fungi, actinomycetes, nitrogen fixing bacteria, phospho-bacteria and potassium bacteria by 58.3, 36.7, 47.3, 56.3 and 56.1% respectively as compared to non-mulched groundnut. Research results have shown that the high levels of carbon dioxide could not penetrate the plastic mulch, escaping only through the holes punched for plants. Hence creating a chimney effect that resulted in abundant CO2 for the actively growing leaves (Lamont 1991). Wind speed within polyethylene film mulched groundnut rows was 0.01 – 0.03 m/s faster compared to non-mulched, which favoured air exchange and CO2 movement. The accumulated soil
Polyethylene mulch and land configurations in groundnut
101
temperature and wind speed increased the photosynthetic efficiency of the crop (Hu et al. 1995). Also in the present study, the maximum rate of CO2 evolution observed under mulched plots might be due to the above said reasons. Crop N, P and K uptake The higher crop N, P and K uptake might be due to higher dry matter production under polyethylene film mulched plots when compared to control. Cumbus and Nye (1985) found that mulching could promote root development, thereby enhancing water and nutrient absorption capacity. Furthermore, the uptake of plant nutrients in the topsoil was enhanced by favourable temperature and moisture conditions. Channabasavanna and Setty (1991) observed that the P content and P uptake were higher under polyethylene film mulch (0.285% and 4.25 kg/ha respectively) when compared to control (0.277 per cent and 1.68 kg/ha). Polyethylene film mulch in a carrot field prevented leaching of fertilizer as it acted as a physical barrier to rainfall. The amount of nitrate and ammonium was highest in the soil under transparent film, followed by black film and bare soil. The amount of nutrients (N, P, K, Ca and Mg) absorbed by the plants from soil was 1.4 – 1.5 times higher in soil under mulch than in the control (Toshio Hanada 1991). Yield components and yield Enhancement in growth characters and yield attributes might contribute to a greater extent in enhancing the pod yield, which is what happened in the present investigation. When biomass and yield components were higher for a particular treatment, especially under white polyethylene film mulch, a higher yield was produced. Higher pod yield under polyethylene film mulched groundnut due to an increase in yield parameters like the number of matured pods/plant, pegging percentage, 100 seed weight was reported by Sanjeev and Ngachan (2001). Golombek et al. (1995) observed that polyethylene film mulch during the early reproductive stages of groundnut crop increased matured seed dry mass per plant by 24% and this effect was mainly due to an increased number of matured seeds and not due to increased seed filling (100 seed weight). The review of pod yield obtained indicated a significant superiority of black polyethylene film mulch only during the winter season. Graham et al. (1995) reported that black polyethylene film mulch was preferable for growing early spring tomatoes (grown as single crop), because of its warming effect on the soil around the roots, while it was believed by the farmers that this black polyethylene film mulch although suitable for tomato, was detrimental to cucumber because the accumulation of heat under mulch would affect cucumber in midsummer for the cropping tomato-cucumber system (tomato planted in April and cucumber in the same field from July to August). One significant problem with the use of white polyethylene mulch was enhanced weed growth beneath the mulch, which would compete with the crop for nutrients and water in addition to reducing the soil-warming effect. Consequently, in this study, herbicides were used in conjunction with the white polyethylene film mulch. Since herbicide was applied to all the treatments, the superiority of white polyethylene film mulch was observed during the autumn season. On perusal of groundnut pod yield data against scientific background, higher pod yield was recorded under flat bed and the yield obtained under flat bed was 22.13% higher than broad beds and furrows and 36.08% higher than ridges and furrows. It was reported that the land configuration broad beds and furrow was working very well under dryland/rainfed situations due to moisture conservation during the dry spell and excess water drainage during the
102
K. Subrahmaniyan et al.
continuous wet spell. Since under irrigated conditions assured moisture supply is given to groundnut crop as per the demand, the land configuration of broad beds and furrows yielded less than flat bed. Sanjeev and Ngachan (2001) reported that the flat bed system had more numbers of functional leaves/plant, DMP and pod yield of groundnut and better soil moisture availability when compared to broad beds and furrows in the irrigated groundnut. The reason for this was that the flat bed system exposed a smaller area to the sun compared to broad beds and furrows and thus more evaporation from the bed edges would have taken place in broad beds and furrows, which resulted in lesser soil moisture availability to the crop and had yielded lower than the flat bed system. Although ridges and furrows are said to be working to the expectation against high radiation, this technology did not work very well under irrigated conditions. This might be due to the nature of soil type where this land configuration was practiced. The present experiment field was red sandy loam soil and hence lower yield was obtained. Sanjeev and Shivani (2001) reported the same scientific background, where only 433 kg/ha of pod yield was obtained under ridges and furrows compared to broad beds and furrows (875 kg/ha) and flat bed (1063 kg/ha) in a clay loam soil under irrigated condition. Summarizing the results, plastic mulching in groundnut with adoption of flat bed land configuration could be an important agricultural practice in semi-arid areas to improve soil properties and hence crop productivity.
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