EFFECT OF GREEN MANURING AND PHOSPHORUS LEVELS IN RICE-BLACKGRAM CROPPING SEQUENCE
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Date
2018
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Acharya N.G. Ranga Agricultural University
Abstract
A field experiment entitled “Effect of green manuring and phosphorus levels in rice-blackgram cropping sequence” was conducted for two consecutive years (2015-2016 and 2016-2017) on sandy clay loam soil of Agricultural College Farm, Bapatla. The experiment was laid out in a split plot design and replicated thrice during kharif season. The treatments consisted of dhaincha green manure crop (M1), sunnhemp green manure crop (M2) and without green manure (M3) as main plot treatments during kharif season and three phosphorus levels to rice crop comprising of 45 kg P2O5 ha-1 (L1), 60 kg P2O5 ha-1 (L2) and 75 kg P2O5 ha-1 (L3) as sub- plot treatments and are replicated thrice.
The rabi experiment was laid out on the same site in a split-split plot design without disturbing the soil for succeeding blackgram crop and each of the kharif plot was divided into three sub-sub plots to receive three doses of phosphorus (D1: No P, D2: 50% RDP and D3:100% RDP) to each plot. The experiment on rice-blackgram sequence as detailed above was repeated on a separate site but in the same block during kharif and rabi in 2015-16 and 2016-17, respectively. Popular cultivars of rice and blackgram viz., BPT-2231 and LBG 752 respectively, were chosen for the study.
Data collected on growth parameters (plant height, drymatter accumulation), yield attributes (panicle length, number of panicles m-2, total number of grains panicle-1, filled grains panicle-1 and test weight), grain yield, straw yield, harvest index and nutrient uptake of rice were subjected to statistical analysis and results indicated that all the characters studied were significantly higher with dhaincha green manure incorporation in combination with 75 kg P2O5 ha-1 recorded significantly higher growth parameters of rice and it was on a par with sunnhemp green manure incorporation in combination along with 75 kg P2O5 ha-1 during both the years of study. Significantly the highest grain yield of rice was recorded with dhaincha green manure incorporated treatment (5592 and
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5587 kg ha-1) when compared to control (5049 and 5003 kg ha-1) during 1st and 2nd year of study respectively. Among the phosphorus levels applied to rice crop the highest grain yield (5545 and 5567 kg ha-1) was recorded with 75 kg P2O5 ha-1 and it was on a par with 60 kg P2O5 ha-1 during both the years of study.
None of the interactions was found to be significant in respect of all the characters studied during both the years of study.
Physical and nutritional (quality) characters of rice grain like amylase content, volume expansion ratio and water uptake were significantly influenced by green manure incorporation only. Whereas, milling quality parameters like hulling, milling and head rice recovery percentages were not significantly influenced by application of green manuring and phosphorus levels to rice crop.
Growth parameters, yield attributes, seed yield, economic returns and nutrient uptake of blackgram were significantly influenced by the green manure incorporation and phosphorus levels to kharif rice crop and different doses of phosphorus to rabi blackgram. Plant height, drymatter accumulation, number of pods per plant, number of seeds pod-1, test weight, seed yield, haulm yield, economic returns and nutrient uptake of blackgram were significantly higher with dhaincha green manure incorporation in combination with 75 kg P2O5 ha-1 to kharif rice crop and 100% RDP to rabi blackgram and it was on a par with sunnhemp green manure incorporation along with 75 kg P2O5 ha-1 to kharif rice crop and 100% RDP to rabi blackgram.
Irrespective of different green manures and phosphorus levels applied to rice crop and phosphorus doses imposed to succeeding blackgram, (No P toP100% ), 100% RDP treatment increased the seed yield significantly in first and second year of study i.e 884 kg ha-1 and 855 kg ha-1 respectively. The maximum seed yield of blackgram was recorded with 100% RDP applied to blackgram and residual effect of dhaincha green manure incorporation to preceding rice crop along with 75 kg P2O5 ha-1 to rice crop
The higher gross, net returns and return per rupee investment was obtained with dhaincha green manure incorporation with 75 kg P2O5 ha-1 to kharif rice crop and 100% RDP to rabi blackgram and it was found on a par with sunnhemp green manure incorporation with 75 kg P2O5 ha-1 to kharif rice crop and 100% RDP to rabi blackgram.
Overall, the field studies conducted for two consecutive years clearly indicated that incorporation of green manures preceeding to rice crop and application of 75 kg P2O5 ha-1 to kharif rice crop and 100% RDP to rabi blackgram treatment had a significant influence in increasing productivity and profitability in rice - blackgram sequence. It is therefore, from this study, it can be concluded that application of green manures with 60 kg P2O5 ha-1 to kharif rice crop and 50 % RDP to succeeding rabi blackgram is the best and the most profitable cropping sequence of Krishna Agro climatic zone of Andhra Pradesh.
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D5614
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