Soil water dynamics, root growth and water and nitrogen use efficiency of rainfed maize (Zea mays) in a semi-arid environment

A field experiment was conducted during kharif season of 2010 and 2011 in a sandy loam soil at New Delhi to study the effect of irrigation (depending on the rainfall) and nitrogen levels (0 kg N/ha, 60 kg N/ha, 120 kg N/ha and 180 kg N/ha) on soil water dynamics, root growth, productivity, water and nitrogen use efficiency of maize (Zea mays L.) (cv HQPM 1). Sufficient and well distributed rainfall during the kharif season of 2010 did not require application of irrigation and hence only nitrogen effects were observed. However in the year 2011, lower rainfall in the early period crop growth required application of a life saving irrigation to all treatments. After that no irrigation was supplied because of adequate and well distributed rainfall. Hence in both the years, only nitrogen effects were seen but not the irrigation effects. At early growth period, poor canopy coverage in no fertilizer treatment exposed the soil for evaporation resulting in lower soil moisture storage. However at peak growth and later stages, lowest soil moisture storage was observed in the treatments receiving 180 kg N/ha followed by 120 kg N/ha, 60 kg N/ha and the 0 kg N/ha treatments, probably because of better crop and root growth and correspondingly higher uptake of water by the crop. The RLD showed significant (P<0.05) variation among the nitrogen treatments in 0-15 and 15-30 cm soil depth for both the years of study. The plant water stress measured in terms of relative water content (RWC) and leaf water potential (LWP) decreased with the increase in nitrogen levels. The water expense efficiency increased significantly both for grain yield and total dry matter production where as partial factor productivity of nitrogen decreased significantly with the increase in nitrogen levels. There was significant increase in the grain yield and total dry matter production of maize with the increase in nitrogen doses. Hence it can be concluded that in years of well distributed and sufficient rainfall 180 kg N/ha will result higher grain and total dry matter yield and water expense efficiency of maize in sandy loam soils of Delhi region.