COST-EFFECTIVE N AND P MANAGEMENT SCHEDULES FOR RICE-BLACKGRAM CROP SEQUENCE

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Date
2006
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PROFESSOR JAYASHANKER TELANAGANA STASTE AGRICULTURAL UNIVERSITY, RAJENDRANAGAR
Abstract
Development of cost-effective nutrient management schedule with integration of green manures, fertilizer-N and non-conventional source of P like phosphate rock would play a vital role in increasing the productivity and profitability of a unique rice-blackgram cropping system adopted in coastal belt of the Krishna-Godavari agro-climatic zone. Two field experiments, one each on N and P management in rice blackgram sequence, were conducted over two years (2002-2004) on sandy clay loam soils of Agricultural College Farm, Bapatla. The study on N management consisted of 16 treatments resulted from four green manuring treatments in main plots viz., (i) no green manuring, (ii) incorporation of sole dhaincha, (iii) incorporation of greengram intercropped with dhaincha rows at flowering and (iv) incorporation of greengram intercropped with dhaincha rows after picking of pods from greengram and four fertilizer-N levels in sub plots as 0, 50, 75 and 100 kg ha-1 arranged in a split-plot design. The study on P management consisted of 36 treatments with the same four green manuring treatments as main plots, with three sources of P application viz., DAP, SSP and phosphate rock with DAP in 1:1 ratio as sub-plots and three times of application of P viz., all as basal, 1/2 basal + 1/2 tillering and 3/4 basal + 1/4 at PI stage as sub-sub plots arranged in a split-split plot design for rice crop. At the end of the crop during the two consecutive years, blackgram was sown as a relay crop in the same plots with the same design to assess the residual effects of treatments given to rice in rice-blackgram sequence. Both the experiments were repeated in another site of the same field. The cultivars used in the study for greengram, blackgram and rice were LGG-460, LBG-645 and MTU-2077, respectively. The growth parameters of rice like plant height, number of tillers and LAI at 60 DAT were significantly increased by green manuring in situ, N levels and by their interaction. Incorporation of sole dhaincha or greengram intercropped with dhaincha rows at flowering significantly increased all growth parameters and advanced the days to 50% flowering compared to other green manuring treatments. Similarly, yield attributing characters such as productive tillers, number of grains panicle-1 (total and filled) and 1000-grain weight including NPK uptake at maturity of rice increased significantly with the incorporation of sole dhaincha or greengram intercropped with dhaincha rows at flowering alongwith fertilizer-N @ 75 or 100 kg ha-1 than that with fertilizer-N alone. Green manuring in situ preceding rice increased the productivity of rice, irrespective of fertilizer-N applied. Green manuring in situ either with sole dhaincha or greengram intercropped with dhaincha rows incorporated at flowering together with 50 kg N ha-1 gave rice productivity on a par with that of application of 100 kg N ha-1 alone showing the possibility to cut back fertilizer-N requirement by 50 kg ha-1 to achieve similar rice crop productivity. The fertilizer-N replacement values for incorporation of sole dhaincha, green gram at flowering and after picking of pods with intercropped dhaincha rows were 54.9, 43.9 and 29.1 kg ha-1 and 50.4, 45.4 and 25.4 kg ha-1 during the first and the second year of study, respectively. Though the fertilizer-N replacement values obtained for incorporation of greengram after picking of pods with intercropped dhaincha rows were lower than those of other green manuring treatments, the additional yield of greengram in this treatment of 660 and 700 kg ha-1 during the first and second year of study, respectively, showed the scope to compensate for reduction in rice productivity following this treatment. Consistently, higher values for all the growth parameters were recorded from P application through DAP than those of phosphate rock and DAP applied in 1:1 ratio or through SSP alone, irrespective of the year of study. The application of P through phosphate rock and DAP in 1:1 ratio was found as effective as that of SSP or DAP in influencing growth when applied with green manuring. Though all the sources of P application, when applied the entire quantity of P as basal only, application of P through DAP reflected in superior rice growth to that of the other sources. Similar to growth parameters, application of P through DAP to rice showed consistent superiority over SSP or phosphate rock and DAP in 1:1 ratio in increasing yield parameters and yield. However, such superiority was not observed when rice was preceded by green manuring in situ, showing the scope for the use of phosphate rock in conjunction with green manuring. Regardless of source, application of P all as basal to rice resulted in higher productivity than that of topdressing. Uptake of NPK by rice also showed similar trend as that of growth and yield. Available NPK status in soil after harvest of rice was higher when green manuring preceded rice than that when fallow preceded, irrespective of the source and time of P application to rice. High residual status of NPK after harvest of rice was reflected in growth and yield of blackgram that followed rice in the sequence. Overall, the field studies conducted over two consecutive years, involving two-crop sequence in every year, clearly indicated the importance of green manuring in increasing the rice and blackgram productivity by economizing the fertilizer-N usage and increasing the P use efficiency of phosphorus sources used including phosphate rock, a non-conventional source.
Description
University : ACHARYA N. G. RANGA AGRICULTURAL UNIVERSITY Year of Submission : 2006 Development of cost-effective nutrient management schedule with integration of green manures, fertilizer-N and non-conventional source of P like phosphate rock would play a vital role in increasing the productivity and profitability of a unique rice-blackgram cropping system adopted in coastal belt of the Krishna-Godavari agro-climatic zone. Two field experiments, one each on N and P management in rice blackgram sequence, were conducted over two years (2002-2004) on sandy clay loam soils of Agricultural College Farm, Bapatla. The study on N management consisted of 16 treatments resulted from four green manuring treatments in main plots viz., (i) no green manuring, (ii) incorporation of sole dhaincha, (iii) incorporation of greengram intercropped with dhaincha rows at flowering and (iv) incorporation of greengram intercropped with dhaincha rows after picking of pods from greengram and four fertilizer-N levels in sub plots as 0, 50, 75 and 100 kg ha-1 arranged in a split-plot design. The study on P management consisted of 36 treatments with the same four green manuring treatments as main plots, with three sources of P application viz., DAP, SSP and phosphate rock with DAP in 1:1 ratio as sub-plots and three times of application of P viz., all as basal, 1/2 basal + 1/2 tillering and 3/4 basal + 1/4 at PI stage as sub-sub plots arranged in a split-split plot design for rice crop. At the end of the crop during the two consecutive years, blackgram was sown as a relay crop in the same plots with the same design to assess the residual effects of treatments given to rice in rice-blackgram sequence. Both the experiments were repeated in another site of the same field. The cultivars used in the study for greengram, blackgram and rice were LGG-460, LBG-645 and MTU-2077, respectively. The growth parameters of rice like plant height, number of tillers and LAI at 60 DAT were significantly increased by green manuring in situ, N levels and by their interaction. Incorporation of sole dhaincha or greengram intercropped with dhaincha rows at flowering significantly increased all growth parameters and advanced the days to 50% flowering compared to other green manuring treatments. Similarly, yield attributing characters such as productive tillers, number of grains panicle-1 (total and filled) and 1000-grain weight including NPK uptake at maturity of rice increased significantly with the incorporation of sole dhaincha or greengram intercropped with dhaincha rows at flowering alongwith fertilizer-N @ 75 or 100 kg ha-1 than that with fertilizer-N alone. Green manuring in situ preceding rice increased the productivity of rice, irrespective of fertilizer-N applied. Green manuring in situ either with sole dhaincha or greengram intercropped with dhaincha rows incorporated at flowering together with 50 kg N ha-1 gave rice productivity on a par with that of application of 100 kg N ha-1 alone showing the possibility to cut back fertilizer-N requirement by 50 kg ha-1 to achieve similar rice crop productivity. The fertilizer-N replacement values for incorporation of sole dhaincha, green gram at flowering and after picking of pods with intercropped dhaincha rows were 54.9, 43.9 and 29.1 kg ha-1 and 50.4, 45.4 and 25.4 kg ha-1 during the first and the second year of study, respectively. Though the fertilizer-N replacement values obtained for incorporation of greengram after picking of pods with intercropped dhaincha rows were lower than those of other green manuring treatments, the additional yield of greengram in this treatment of 660 and 700 kg ha-1 during the first and second year of study, respectively, showed the scope to compensate for reduction in rice productivity following this treatment. Consistently, higher values for all the growth parameters were recorded from P application through DAP than those of phosphate rock and DAP applied in 1:1 ratio or through SSP alone, irrespective of the year of study. The application of P through phosphate rock and DAP in 1:1 ratio was found as effective as that of SSP or DAP in influencing growth when applied with green manuring. Though all the sources of P application, when applied the entire quantity of P as basal only, application of P through DAP reflected in superior rice growth to that of the other sources. Similar to growth parameters, application of P through DAP to rice showed consistent superiority over SSP or phosphate rock and DAP in 1:1 ratio in increasing yield parameters and yield. However, such superiority was not observed when rice was preceded by green manuring in situ, showing the scope for the use of phosphate rock in conjunction with green manuring. Regardless of source, application of P all as basal to rice resulted in higher productivity than that of topdressing. Uptake of NPK by rice also showed similar trend as that of growth and yield. Available NPK status in soil after harvest of rice was higher when green manuring preceded rice than that when fallow preceded, irrespective of the source and time of P application to rice. High residual status of NPK after harvest of rice was reflected in growth and yield of blackgram that followed rice in the sequence. Overall, the field studies conducted over two consecutive years, involving two-crop sequence in every year, clearly indicated the importance of green manuring in increasing the rice and blackgram productivity by economizing the fertilizer-N usage and increasing the P use efficiency of phosphorus sources used including phosphate rock, a non-conventional source.
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