Mercy GeorgeBeena JacobKAU2019-02-212019-02-211994170511http://krishikosh.egranth.ac.in/handle/1/5810096248PGAn experiment was conducted at the Agricultural Research Station, Mannuthy during the summer and kharif seasons of 1993 to evaluate the effect of cowpea and groundnut residue incorporation on the productivity of succeeding rice crop in comparison to a green manure Sesbania rostrata and a pre-rice fallow under four levels of N (0, 35, 70, and 105 kg/ha). The experiment was laid out in a split plot design with four replications. Biomas yield on dry weight basis was higher for groundnut and sesbania (7.0 t/ha) while N accretion was higher from cowpea (133kg N/ha). Extractable ammonium in the soil was the highest in sesbania incorporated treatments and minimum in plots preceded by fallow. Sesbania underwent faster mineralization compared to residues and mineral-N accumulation reached a peak 15 days after incorporation. Cowpea residue and sesbania incorporation resulted in higher plant height and tiller production. The dry matter production of rice by incorporation of sesbania was on par with cowpea residue when 70 kg N/ha was applied for rice. Sesbania incorporated treatments recorded the highest leaf area index whereas chlorophyll content at boot leaf stage was maximum in cowpea residue treated plots. Number of spikelets per panicle and total number of spikelets per panicle were higher in sesbania incorporated treatments which was on par with that of cowpea residue treated plots. Grain yield was higher after sesbania (3.24 t/ha) and cowpea residue (3.23 t/ha) incorporation and sesbania along with 70 kg N/ha produced the highest grain yield of 3.74 t/ha. N, P and K contents of grain were maximum when rice was grown after cowpea residue incorporation. Total uptakes of N, P and K at harvest were also the highest after cowpea residue incorporation which was statistically similar to that of sesbania incorporation. Even though NPK uptake increased by application of 105 kg N/ha, they were on par with 70 kg N/ha. Groundnut-rice system and sesbania-rice system were comparable in retaining a higher level of soil fertility. Net income was higher from groundnut-rice system whereas return per rupee invested was higher for cowpea-rice system.ennullThesis