LAUSR

Abstract Field experiments were conducted during summer and rainy ( kharif ) seasons (April-November) of 2009 and 2010 for two consecutive years at the research farm of the Indian Agricultural Research Institute, New Delhi. The objectives of this study was to determine the effects of summer green manuring crops [ Sesbania aculeata (Dhaincha), Crotalaria juncea (Sunhemp) and Vigna unguiculata (Cowpea)] and zinc (Zn) fertilizers [EDTA-chelated Zn (12% Zn), ZnSO 4 .7H 2 O (21% Zn), ZnSO 4 .H 2 O (33% Zn), ZnO (82% Zn) and ZnSO 4 .7H 2 O + ZnO (50% + 50%)] and on the diethylene triamine penta-acetic acid (DTPA) extractable (available) Zn concentration in soil and total Zn content in of Basmati rice cv. ‘Pusa Basmati 1’plants at periodic intervals. Beneficial effects of summer green manuring crops and Zn fertilizers on DTPA-extractable (available) Zn concentration in soil and total Zn content in dry matter of Basmati rice at periodic intervals were observed, with significant increases in all the determined parameters, in comparison with the control (no Zn application or summer fallow). The rates of increase varied among summer green manuring crops and Zn fertilizers during both the years. Among the summer green manures, incorporation of Sesbania aculeata led to a significant increase in mean Zn content in Basmati rice grain (31.5 and 32.4 mg kg −1 grain) and straw (167.5 and 172.1 mg kg −1 straw) compared with Crotalaria juncea , Vigna unguiculata and summer fallow treatments. Among the Zn fertilizers, significant improvement in Zn concentration in Basmati rice dry matter and DTPA-extractable Zn content in soil at various growth stages were recorded with EDTA-chelated Zn (12% Zn) application, followed by ZnSO 4 .7H 2 O (21% Zn), ZnSO 4 .H 2 O (33% Zn), ZnSO 4 .7H 2 O + ZnO (50% + 50%), ZnO (82% Zn) and control (no Zn application). The highest mean Zn concentration in Basmati rice grain (33.9 and 35.7 mg kg −1 grain) and straw (173.5 and 177.4 mg kg −1 straw) was recorded with EDTA-chelated Zn (12% Zn) application in 2009 and 2010, respectively. The ZnSO 4 .7H 2 O (21% Zn) application was the second best treatment after EDTA-chelated Zn (12% Zn), but was statistically inferior to it. The lowest values were recorded with control (no Zn application) during both the years of experimentation. The amount of Zn content in soil has been found to be significant positively correlated with the Zn concentration of Basmati rice dry matter during both the years of experimentation. Significantly higher levels of residual fertility in soil after harvest of Basmati rice was observed with application of EDTA-chelated Zn (12% Zn) and Sesbania aculeata incorporation compared with rest of Zn sources and summer green manures during both the years.