RADHA KRISHNA MURTHY, VVIBHAJAM SAGAL KIRAN, B2020-03-042020-03-042019http://krishikosh.egranth.ac.in/handle/1/5810144160D5948A field experiment entitled “Response of rice sorghum cropping sequence to prevailing weather and nitrogen levels” was conducted for two consecutive years (2017-18 and 2018-19) on clay loam soils of Agricultural College Farm, Bapatla. The soil pH was slightly alkaline in reaction, medium in organic carbon, low in available nitrogen, medium to high in available phosphorus and high in potassium. The kharif experiments on rice consisted of three varieties viz., NLR145(V1), BPT-5204(V2) and NLR-34449(V3); as main plot treatments. Four nitrogen levels to rice viz., 60 kg N ha-1 (N1), 80 kg N ha-1 (N2), 100 kg N ha-1 (N3) and 120 kg N ha-1 (N4) as sub plot treatments. All the treatments were randomly allocated in three replications in a split plot design for kharif seasons. The rice crop was sown as direct seeded rice. The kharif imposed treatments were evaluated rabi seasons with RBD design in both the years of study on sorghum grown as sequence. Data collected on growth parameters, yield attributes, yield, nutrient uptake of rice and economic returns were subjected to statistical analysis which indicated that all the characters studied were significantly higher with the rice variety BPT-5204 with the application of 120 kg N ha-1. Whereas, significantly lower values were observed with rice variety NLR-34449 with application of 60 kg N ha-1 during both the years of study and in pooled data. xxiv A significant interaction between varieties and levels of nitrogen in rice was observed for drymatter accumulation at 90DAS during both the years, number of panicles m-2 during 1st year of study and grain yield during both the years with the treatmental combination of variety BPT-5204 and 120 kg N ha-1 and significantly superior to other treatmental combinations. Higher values of all weather health indices/climatic normals viz., GDD, HTU, PTU, TPR, HUE, HtUE, PtUE, PTI and RUE were recorded with variety BPT-5204(V1) followed by NLR-145 and NLR-34449 during both the years of study. Among the nitrogen levels, application of 120 kg N ha-1 recorded the optimum values of all weather health indices during both the years of study. The influence of weather health indices was found to be optimum to produce highest yields. Significant linear relationship was observed for drymatter and grain yield of all the three varieties and four nitrogen levels tested with weather health indices viz., GDD, HTU, PTU, TPR, HUE, HtUE, PtUE, and PTI during both the years of study. These regression equations could be applied to predict rice growth and yield using daily information on temperature, photoperiod, day length and sunshine hours during the crop season, to predict rice yields grown under different N levels. Significant and negative correlation was observed with the rice grain yield and micrometeorological parameters viz., canopy air temperature, canopy temperature and soil temperature for both the years of study and regression equations could be applied to predict rice yields under different nitrogen levels Growth parameters, yield attributes, grain yield, stover yield, nitrogen uptake and economic returns of zero till sorghum were influenced significantly by sorghum crop sown after the harvest of rice variety NLR-34449 and was on par with the variety NLR-145 and among the residual effect of nitrogen levels indicated that 120 kg N ha-1 resulted significantly superior over to residual treatments. The availability of N, P and K status after harvest of sorghum decreased due to high uptake of nutrients during both the years of study. The rice crop in both the years experienced 27.10C- 32.20C and 1 to 6 hrs day-1 bright sunshine hours during vegetative stages; 26.60C-29.80C and 1 to 6 hrs day-1 bright sunshine hours during reproductive phase and 22.40C26.30C and 4 to 6 hrs day-1 bright sunshine hours during maturity phases. The sorghum crop in both the years experienced 21.80C- 23.70C and 4 to 7 hrs day-1 bright sunshine hours during vegetative stages, 22.80C-28.10C and 6 to 8 hrs day-1 bright sunshine hours during reproductive phase and 27.60C-29.30C and 8 to 9 hrs day-1 bright sunshine hours during maturity phases. These are found to be most congenial and optimum for rice–sorghum crop sequence. The production potential was higher in rice-sorghum cropping sequence under the above weather conditions with early date of sorghum sowing and 120 kg N ha-1 residual nitrogen. xxv Path coefficient analysis indicated that there is a direct and indirect effects of morphological parameters on grain yield of rice varieties. Step down regression analysis indicated significant relation for high yields of three rice varieties with maximum temperature at vegetative stage, relative humidity in the morning at maturity, relative humidity in the evening at vegetative stage, sunshine hours at reproductive stage and rainfall at reproductive and maturity. These are: Y = -70894.95+610.29(RH13)+358.19(RH21)-28.43(RF2) for NLR-145 Y = -456495.33-8517.20(MAT1)+9233.55(RH11)+20.87(RF3) for BPT-5204 Y = 73989.44-1866.96(MAT1)-1214.78(SSH2)-19.41(RF3) for NLR-34449en-USnullThesis