IMPACf OF FERTILIZATION TO RICE BASED ON AN OPTIMUM NUTRIENT TREATMENT ONYIELD OF RESIDUAL BLACK GRAM AND ITS ECONOMICS

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1 Legume Res.. 28 (1) ; IMPACf OF FERTILIZATION TO RICE BASED ON AN OPTIMUM NUTRIENT TREATMENT ONYIELD OF RESIDUAL BLACK GRAM AND ITS ECONOMICS M.R. Latha and V. Murugappan Department of Soil Science and Agricultural chemistry. Tamil Nildu Agricultural University. Coimbatore India ABSTRACf Field experiment was conducted in an experimental soil belonging to Kalathur series in Cauvery Delta in the rice-rice-pulse system to evaluate the influence of Optimum Nutrient Treatment evolved on the basis of nutrient sorption studies and experimental soil initial analysis, on the yield in rice and to study the subsequent residual effect of the imposed treatments on the yield of blackgram. The results of the experiment revealed that considerable amounts of residual N, P and K were left in the soil due to application of N, P and K fertilizers to the kwuvai and thaladl season rice crops. Thiswas evidenced in the enhancement of grain and haulm yields of blackgram doe to N or P or K fertilization. Zn omission from the ONT did not attain statistical significance in its influence onblackgram yield. Blanket fertilizer application reduced the yield of nutrients. Economics of fertilization also revealed the usefulness of the optimum nutrient treatment over the blanket recommendation. INTRODUcnON Rice-rice-pulse is the most prevalent cropping system in the major rice growing tract of Tamil Nadu, viz., the Cauvery delta zone comprisingof ltichy, Thanjawr, Tiruvarur and Nagapattinarn districts. Also, pulses are generally raised as a residual crop to utilize the available nutrients and residual moisture after rice crops grown during kuruvai (June September) and thajadi (October-February) seasons in this area. The yield of pulses is considerably low due to poor management practices. Nutrient management is an essential component in any crop management. The present study was attempted to study the residual effect of fertilization by Optimum Nutrient Treatment(ONT) defined based on nutrient sorption studies and initial analysis of soil and blanket dose of fertilizers applied to rice crops in the two seasons prior to growing of residual pulse crop. MATERIAL AND METHODS Field experiment was conducted in a farmer's holding for three seasons in succession during in order to define fertilizer optima for the rice crops and also to evaluate the residual effect of fertilizer application on blackgram. Rice (var. ADT 36) in kuruvai season (June-September) followed by rice (var. CO 43) in thajadi season (October-February) and followed by a residual blackgram (var. T9) (February-May) were the cropping sequence fouowed in the experiment. l'he experimental site was located in Ramapuram village in Thanjavur district. The experimental soil belonged to Kalathur series. This soil is a benchmark soil in this zone with a distribution of 1.61lakh ha (13 per cent of the total area of the zone). Thesite is located at 10 50' North latitude and 78 50' East longitude atanaltitude of 54 m above MSL. The mean annual rainfall of the region is 906 mm. The mean maximum and minimum temperatures are 32.6 and 23.3 C, respectively. The relative humidity ranges from 68.5 per cent (1416 hrs) to 79.3 per cent (07 16 hrs). The monthly mean evaporation rate is 280 mm. In the experiment, there were 12 treatments. The ONT formed the central treatment. In each case of N, P and Kthere were three more levels, viz., a zero level, one below and another above the ONT level. Except the variable nutrient in each case, other nutrients were kept equal to that of ONT. All these ten treatments received

2 Vol. 28, No. I, Table 1. Treatments for the field trial Treatments N P K Zn (kg ha 1) N O K NP NP NP2K N2P o K N 2 P j K NPJ NP2K O NP2K j NP2KJ NP2K2-Zn Blanket Fertilizer ADT36 rice CO 43 rice Zn as in ONT. Besides there was one treatment which was ONT minus Zn. Also a blanket fertilizer treatment was included for comparison. The treatments for field trials imposed for rice is given in Table 1. The treatments were replicated four times in a randomized block design (RBD). The fertilizer prescription equation from the All India Soil Test Crop Response Study Project of the Department of Soil Science, Tamil Nadu Agricultural University, Coimbatore was used for fixing the N fertilizer rates (Anonymous, 2000). For other nutrients, the ONT formulated through laboratory studies and green house experimentsformed the basis for fixing the rates. The fertilizer prescription equation used as the basis to fix the N rates for Kalathur soil series is given below: FN = 5.29 T SN where FN is the fertilizer N in kg ha- I, T is the yield target in quintals ha- I and SN is alkaline KMn0 4 -N in kg ha- I. In both cases, for the KMnO4-N in the initial soil and for a yield target of 70 quintals ha- I the FN was calculated. Besides, a zero level and one below and one above this level of N corresponding to 70 quintals/ha of yield target were fixed for each experimental soil. In the ONT, P level was 12 mg kg-i. Therefore 24 kg P ha- I formed the central treatment. On the basis followed for N, other P rates for the experiments were arrived and are shown in Table 1. The K level in ONT was me 100 g -I in Kalathur series. This worked out to be 35 kg ha- I, which formed the central treatment. Similar to that of Nand P, other K rates were arrived and are presented in Table l.the level of Zn in ONT was 3.25 mg kg- I for Kalathur series. Therefore 6.5 kg Zn ha -I formed the Zn level in ONT. Other than this, there was only one ONT minus Zn treatment (Table 1). According to the Crop Production Guide of Tamil Nadu Agricultural University, the recommended level of N, P, K and Zn for ADT 36 rice (short duration variety) are 120, 17, 28 and 5.5 kg ha- I respectively. The recommended level of blanket fertilizer for CO 43 rice, which is a medium duration variety is 150, 22, 42 and 5.5 kg ha- I of N, P, K and Zn, respectively. The fertilizer sources used for the experiment were urea for N (46 per cent N), superphosphate for P (16 per cent water soluble PP5), muriate of potash for K (60 per cent KP) and zinc sulphate for Zn (22 per cent Zn). Blackgram (var. T9) was raised as a residual crop after the second rice crop. The land was prepared to necessary tilth by spade digging without disturbing the plot boundaries.

3 14 LEGUME RESEARCH Table 2. Grain and haulm yield of residual T9 blackgram in Kalathur series Treatments N O K 2 NP2K2 N 2 K 2 (ONn N 3 K 2 Np o K 2 NP 1 K 2 N2P3 NP2 K " N2P1 N 2 K 3 ONT-Zn Blanket fertilizer Mean SE(d) CD (P = 0.05) Grain yield (kg ha- 1 ) Haulm yield (kg ha- ' ) Three blackgram seeds per hole were dibbled by adopting spacing of 30 x 10 em and after germination, two healthyseedlings in each hole were maintained. The crop was harvested at maturity. The grainandstrawyield of rice crops and grain and haulm yield of blackgram were recorded treatment wise at the time of harvest. The data collected from field experimentswere subjected to statistical analyses using the computer software IRRISTAT (lrri, 1993). The economics of fertilization due to these two approaches were worked out for the cropping system. RESULTS AND DISCUSSION The results of the experiment revealed that considerable amounts of residual N, P and K were left in the soil due to application of N, P and K fertilizers to the previous kuruvai and thaladi season rice crops. This was evidenced in the enhancement of grain and haulm yields due to N or P or K fertilization (Table 2). Jeyaraman (19B7) also reported expression of such a residual effect of N fertilization to rice onthe succeedingblackgram crop. Gopala Rao et a/. (1991) had recorded significant increases in yield of residual b!ackgram due to P fertilization to the preceding rice crop. Yield enhancement in the residual blackgram due to N. P and K fertilization to the preceding two rice crops was also reported by Rehman et a/. (19BB), Indulkar and Malewar (1990) and Selvi and Ramaswami {1995}. However, the levels of these fertilizer nutrients did not vary grain and haulm yields among themselves in the present study. Withholding Zn from ihe ONT did not influence blackgram response, but grain and haulm yields were significantly lower with blanketfertilizer doseascomparedtothe ONT. The economics of fertilization through blanket recommendation and optimum nutrient treatment were worked out and given in Table 3. It could be inferred that the ONTfaired better in terms of profit due to fertilization in both the rice crops. In ADT 36 Rice, there was monetary gain of Rs.3,655/- in ONT than the blanket fertilizer dose. The figure for CO 43 rice was Rs.1,142/- and T9 blackgram was Rs.735 respectively. In kuruvai {June-Sep} season the yield of rice is higher than the tha/adkoct- Feb} season due to the favourable weather and increased nutrient use efficiencies leading to higher profits. The profit due to ONT as compared to blanket dose is higher in kuruvai due to the larger difference in nitrogen between these two tre'ltments as compared to the tha/adi season. Since Blackgram was raised as a residual crop without the application of fertilizers and its yield was still higher under

4 l\;l Z... l\;l o (J1... (J1 Table 3. Economics of fertilization in rice-rice-pulse croppingsystem through ONT and blanket fertilizer treatments Treatments Grain yield (kg/ha) Value of grain yield (Rs.)' Cost of fertilizers (Rs.)' Profit due to fertilization (Rs.) Fertilizer by optimum nutrient treatment ADT 36 rice CO 43 rice T9 Blackgrarn ADT 36 rice CO 43 rice 27,936 31,089 T9 Blackgram ADT 36 rice CO 43 ric" T9 ADT 36 rice CO 43 rice BJackgram 5,424 2,866..2,866 25,070 28,223 T9 Blackgram Fertilizer as blanket dose ,680 29,897 4,836 2,265 2,816 21,415 27,081 6,045, Economics were calculated using a price of per kg of N as Rs. 8.67, PP5as Rs. H.06, Kp as Rs. 6.20, Zn as Rs and one kg of ADT 36 rices Rs. 4.00, CO 43 rice as Rs.4.75 and T9 Blackgram as Rs ,780

5 16 LEGUME RESEARCH ONT as compared to the blanket dose of fertilizer, the evolved ONT is found to be better in its residual effect on blackgram. Thusfertilization to previous rice crops had profound influence on blackgram crop. Since, pulses are grown as a residual crop to utilize the available nutrients and moisture, the study on the effect of fertilization to rice crops on the yield of residual pulse in a Rice-ricepulse cropping system assumes significance. ACKNOWLEDGEMENT Theauthorwishes toacknowledgethe financial support provided by the Potash Phosphate Institute of Canada - India Programme (PPIC-IP) for the investigation. REFERENCES Ancnymous (2000). Compendil1m of Research on Soil Test Crop Response Studies and rationalized fertilizer recommendations for crops in Tamil Nadu ( ). Gopala Rao. P. et al. (1991). Indian J. Agron., 36(2): lndulkar. B.S. and Malewar, G.U. (1990). Fertil. News, 35: lrri (1993). lrristat, Biometrics Unit, lnt. Rice Res. Inst., Los Banos, Phillipines. Jeyaraman, S. (1987). Indian J. Agron., 32(4): Rehman, A. etal. (1988). Nudeus(Karachi), 25: Selvi, S. and Ramaswami, P.P. (1995). Madras Agric. J., 82: