Productivity and nutrient uptake of maize (Zea mays)–wheat (Triticum aestivum) cropping system under different bio-sources and nitrogen levels

A field experiment was conducted during 2006–07 and 2007–08 at New Delhi to assess the growth, yield and nutrient uptake behavior of maize (Zea mays L.)–wheat [Triticum aestivum (L.) emend. Fiori & Paol.] cropping system under different bio-sources and nitrogen levels. Application of vermicompost (VC) equivalent of 60 kg N/ha, being at par with farmyard manure (FYM) equivalent of 60 kg N/ha recorded taller plants with more leaf area index (LAI) and grains/cob, resulting in 22.7 and 23.8% enhancement in grain yield of maize over control in 2006 and 2007, respectively. The residual fertility of FYM resulted in higher plant height, LAI effective tillers/meter row length and grains/spikelet of wheat over the VC and control. Grain yield of wheat with residual of FYM increased to the tune of 21.2 and 24.1% over the control; and corresponding increase over the VC application was 9.1 and 10.3% in first and second year, respectively. Similar response in respect of biological yield and N, P, K and Zn uptake to organic sources was also found. Increasing N doses had beneficial effect on growth and yield attributes of both the crops resulting in 21.5, 38.9 and 48.9% increase in grain yield of maize; and 30.0, 47.7 and 61.2% increase in grain yield of wheat due to application of 40, 80 and 120 kg N/ha over the control, respectively. The biological yields of maize and wheat and nutrients uptake by cropping systems also improved with increasing nitrogen levels. The net returns/ha from maize–wheat cropping sequence was maximum with the application of FYM. Increasing N doses showed the increasing pattern of net returns up to 120 kg N/ha. Expected N balance remained positive with organic sources and N levels. The data on gain or loss of N in soil indicated that N content in soil showed the positive trend with Azotobacter, FYM and 80 and 120 kg N/ha.