Madras Agric. J., 98 (10-12): 344-346, December 2011

Short Note

Effect of Long Term Fertilization on Phosphorous Fractions Under Finger Millet-Maize Cropping Sequence S. Hemalatha1* and S. Chellamuthu2 1

Department of Soil Science & Agricultural Chemistry, 2 Water Technology Centre, Tamil Nadu Agricultural University, Coimbatore - 641 003.

A long term field experiment on different doses of graded fertilizers with and without FYM under finger millet-maize cropping sequence is in progress at the Tamil Nadu Agricultural University, Coimbatore, since 1972. The effect of continuous fertilization on soil inorganic Phosphorus (P) fractions was studied after 36 years of cropping cycle on a sandy clay loam soil. Long-term application of 150 % NPK increased the soil inorganic P fractions followed by 100 % NPK + FYM. But the availability of P is higher in the plots receiving 100 % NPK + FYM. The integrated nutrient management significantly increased the availability of the nutrients. Key words: Long term fertilization, finger millet - maize, inorganic P fractions

Phosphorus (P) is one of the seventeen nutrients essential for the plant growth. It is the nutrient, which records high residual efficiency. So the application of P through manures and fertilizers over years would build up the soil reserves due to the fixation of appreciable portions of the applied phosphorus into forms of low solubility. The total P content of Indian soils ranged from 100 to 200 ppm (Tandon, 1987). The total P in soil consists of inorganic and organic P forms. The major active forms of inorganic P are aluminium P (Al-P), iron P (Fe-P) and calcium P ( Ca-P) while the occluded P becomes less active. All these forms exists in all soils, but generally Al-P and Fe-P are more abundant in acid soils, where Ca-P is dominated in neutral and alkaline soils. The present investigation was undertaken to study the effect of long term application of graded doses of inorganic fertilizers with and without FYM on inorganic P fractions in the finger millet–maize cropping sequence (after 36 years) grown on an Inceptisol at Coimbatore. Materials and Methods The investigation was carried out at Tamil Nadu Agricultural University, Coimbatore in the on going long – term fertilizer experiment laid out during 1972 for studying the effects of various fertilizer treatments on P fractions with fixed cropping rotation consisting of finger millet–maize. The climate of this area is semi arid tropical with a dry season from January to June and wet season upto December. Temperature varies from 31ºC ( May – June ) to 21º C ( December – January). The soil of the experimental site is fine montmorillonitic, isohyperthermic and classified as Vertic Ustropept. The experiment consisted of ten treatments and was laid out in a randomized block *1Corresponding author email: [email protected]

design with four replications. The treatment details are (T1) – 50 % NPK, (T2) – 100 % NPK, (T3) – 150 % NPK, (T4) – 100 % NPK + Hand weeding (HW), (T5) – 100 % NPK + ZnSO4 (Maize alone), (T6) – 100 % NP, (T7) – 100 % N, (T8) – 100 % NPK + FYM (Finger millet alone), (T9) – 100 % NPK (-S), (T10) – Control. The optimal amounts of N, P2O5 and K2O (100 % NPK) are 90:45:17.5, 135:67:5.35 kg ha-1 for finger millet and maize respectively. The fertilizers used were urea, single super phosphate, diammonium phosphate (T9 only), muriate of potash and zinc sulphate. The application of FYM @ 10 t ha1 was done once a year at the time of planting of finger millet and fertilizers were applied to each crop in the rotation. The size of the plot was 10 m x 20 m with 5 m wide strip separating each replication. Surface soil samples (0-15 cm) were collected treatment wise. The soil material was air dried, passed through a 2 mm sieve and stored. The soil inorganic phosphorus fractions (Saloid P, Al-P, Fe-P, Ca-P and reductant soluble P) were estimated by the method described by Peterson and Corey (1966). Results and Discussion The range of saloid – P content was from 10.79 to 26.2 ppm in absolute control to 150 per cent NPK (Table.1). Lower saloid – P contents were observed under 100 per cent N and control plots. The 150 per cent NPK registered a spectacular increase in saloid – P than the above two levels. Hand weeding or ZnSO4 application or inclusion of S free sources in fertilizer schedule did not increase the saloid – P content over that of 100 per cent NPK treatment and these treatments were on par. This fraction was the least among the inorganic P forms evaluated.

345 Table 1. Effect of treatments on soil inorganic P fractions under long-term fertilization Saloid P

Al-P

Fe-P

Rs-P

Ca-P

T1- 50% NPK

12.78

19.18

18.68

18.71

112.82

T2- 100% NPK

16.97

34.87

20.98

19.03

165.40

T3- 150% NPK

26.21

50.24

31.45

31.26

257.93

T4- 100% NPK+ HW

16.52

41.34

21.94

21.71

194.38

T5- 100 %NPK+ ZnSO4

15.98

45.70

21.84

21.87

198.30

T6- 100% NP

16.50

39.88

19.84

18.43

199.15

T7- 100% N

11.75

21.81

18.66

14.33

118.25

T8- 100% NPK+ FYM

19.38

42.94

22.15

27.56

137.32

T9- 100% NPK (S-free)

16.77

33.66

18.74

15.22

101.31

T10- Absolute control

10.79

18.88

14.97

12.40

91.57

SED

0.55

1.42

0.51

0.73

1.86

CD (P=0.05)

1.13

2.93

1.06

1.51

3.81

Additions of graded doses of fertilizer phosphorus had resulted in considerable increase in the saloid form of phosphorus. The increase might be due to the transformation of applied P into Saloid and Al-P under aerobic conditions in the first instance and then to Ca-P with time (Jain and Sarkar, 1979) and to the formation of dicalcium phosphate in the calcareous soil which is usually recovered during fractionation as saloid (Singh and Sarkar,1986). Control and N alone treatments recorded the lowest values as they did not receive P fertilization. The Al-P content varied from 1.18 ppm in absolute control to 50.24 ppm in 150 per cent NPK. Among the treatments, the highest concentration was under 150 per cent NPK (50.24) followed by 100 per cent NPK + FYM (42.94 ppm) and least being in the control plot (19.18 ppm). Progressive increase in the quantum of NPK applied from 50 to 150 per cent of optimum level was accompanied by a corresponding increase in the amount of Al-P. In fact 50 per cent level of NPK could not produce any significant increase in Al-P (19.18 ppm) over that of control (18.88 ppm). These two treatments being on par with each other. All the other treatments have increased the Al-P over that of control. Aluminium phosphate recorded the highest concentration next to Ca-P which dominated all the inorganic fractions of P. However, the relative concentration of Al-P was lower as compared to Ca-P due to the calcareous nature of experimental soil. Increased Al-P with higher rates of fertilizer P (Rokima and Prasad, 1991) was also observed in the long term fertilizer experiment of Palmpur (Sudhir Agarwal et al., 1987) The amount of Al-P in the control was the lowest due to continuous cropping and removal of P from the soil native reserve. In contrast, the Al-P concentration in the treatment which did not receive

P fertilizer (100 per cent N) continuously produce equal amount to that of 100 per cent NPK treatment. This is attributed to the release of P from the soil reserve sites to meet the crop requirement. Among the treatments continuous addition of 150 per cent optimal NPK recorded higher values of Fe-P in the post harvest soils of finger millet during the year 2008 -09. Among the treatments 100 per cent NPK, 100 per cent NPK + ZnSO4, 100 per cent NPK + hand weeding were on par with each other. The present study revealed that the Fe-P content of the soil increased in the combined treatment of organics with inorganics. This could be attributed to the formation of Fe-P due to the reduction of Fe3+ to Fe2+ resulting from the release of organic acids from the decomposition of organic materials are observed by Jaggi (1991) or due to the shift in the P equilibrium to Fe-P as observed by Tripathi and Minhas (1991) and Rokima and Prasad (1991). During the period of investigation, the reductant soluble P ranged between 12.40 and 31.26 ppm. Among the treatments, the highest reductant soluble P was associated with 150 per cent NPK, while the second highest was under the control in both the years. ZnSO 4 addition increased the reductant soluble P over that of all other treatment combinations. Exclusion of S from the fertilizer schedule reduced the P over that of S containing sources. Among the treatments, 150 per cent NPK treatment recorded higher amount than rest of the treatments for the crop evaluated during the study period. The reductant soluble phosphate represents the occluded form of phosphates on soil components and enrichment of a deficient soil with P makes it conducive for build-up of various P fractions including reductant soluble P (Singaram and Kothandaraman, 1992).

346 Among the P fractions estimated, Ca-P was the dominant form. The Ca-P status in the soil varied from 92 to 258 ppm. The Ca-P status was generally lower in control plot (91.56) and higher in 150 per cent NPK (258 ppm). Similar to reductant soluble P, exclusion of S from the fertilizer schedule reduced the Ca-P over that of S containing sources. Due to the calcareous nature of the experimental soil the dominating inorganic fraction of P was the Ca-P accounting for nearly 62 per cent of the total inorganic P and 39 per cent of the total P (Kothandaraman and Krishnamoorthy, 1977).Increasing rates of P addition resulted in concomitant increase in the CaP of the soil possibly due to the higher concentration of soil Ca which might have reacted with the applied P into the system as opined by Singaram and Kothandaraman (1993). Besides, the amount of Ca added to the soil was considerable since the source of fertilizer P being super phosphate which contains considerable amount of external source of P application resulted in lower Ca-P concentration under those treatments which did not receive P. Conclusion All the P fractions increased with increasing levels of fertilizer doses and were higher under continuous application of 150 per cent NPK followed by 100 per cent NPK + FYM. Among all the fractions Ca-P dominated, the rest of the fractions and this may be due to the calcareous nature of the experimental soil. References Jaggi, R.C.1991. Inorganic phosphate fractions as related to soil properties in some representative soils of Himachal Pradesh. J. Indian Soc. Soil Sci., 39:567568.

Jain, J.M. and Sarkar, M.C.1979. Transformation of inorganic phosphorus under field conditions and its effect on P uptake and grain yield of wheat. In: Phosphorus in soil crops and Fertilizers. Bull. Indian Soc. Soil Sci.,12:460-464. Kothandaraman, G.V. and Krishnamoorthy, K.K. 1977. Distribution of inorganic phosphorus fractions in Tamilnadu soils. Madras Agric. J., 64: 516-521 Peterson, G.W. and Corey, R.B.1966. A modified Chang and Jackson procedure for routine fractionation of inorganic soil phosphates. Soil Sci. Soc. Am. Proc., 30: 563-565 Rokima, J. and Prasad, B.1991. Integrated nutrient mgt-II. Transformations of applied P into inorganic P fractions in relation to its availability and uptake in calcarious soil. J. Indian Soc. Soil Sci., 39: 703-709. Singaram, P. and Kothandaraman, G.V. 1992. Residual, direct and cumulative effect of phosphate fertilizers on inorganic phosphorus fractions in soils after finger millet (Elusine coracana) Maize (Zea mays) cropping sequence. Indian J. Agric. Sci., 62:118-123. Singaram, P. and Kothandaraman, G.V. 1993. Effect of P sources on phosphorus uptake by finger millet and changes in inorganic P fractions. J. Indian Soc. Soil Sci., 41: 588-590. Singh, K.P. and Sarkar, M.C.1986. Effect of fertilizer phosphorus and farmyard manure on inorganic phosphorus transformation in soils. J. Indian Soc. Soil Sci., 34:209-212. Sudhir Agarwal,T., Singh, A. and Bharadwaj, V. 1987. Inorganic soil phosphorus fractions and available P as affected by Long Term fertilization and cropping pattern in Nainital Tarai. J. Indian Soc. Soil Sci., 35:2528. Tandon, H.L.S. 1987. Phosphorus Research and Agricultural Production in India. FDCO, New Delhi, pp.S III / 2 (1/ 12) Tripathi, D. and Minhas, R.S.1991. Influence of fertilizer phosphorus and farmyard manure on transformation of inorganic phosphate. J. Indian Soc. Soil Sci.,39: 472-476.

Received: March 2, 2011; Accepted: November 21, 2011