Nitrogen (N) is the most critical externally added input for any crop production system. The half of the global population directly or indirectly depends on nitrogenous fertilizers for food supply. Today, Rice, wheat, and maize are consuming more than 90% of total nitrogenous fertilizer used in cereals. Underuse of nitrogen is associated with lower crop production while overuse leads to several soil and environmental related consequences. Therefore, response to applied nitrogen and its use efficiency have to be monitored properly for obtaining the maximum potential and sustainable yield. Efficiency of applied nitrogenous fertilizers is very low due to its various losses i.e. volatilization, leaching, surface runoff and denitrification from soil-plant system. Therefore, the proper understanding of advanced soil and plant management practices which helps in enhancement of nitrogen recovery efficiency is one of the key factors to enhance crop output, decreasing cost of cultivation, and to maintain environmental quality which ultimately adds towards the goal of achieving long term sustainable production system. In this review, an attempt has been made summarize the locally as well as scientific soil and crop management technologies used for improving use efficiency of applied N. This paper also discusses nitrogen cycling in soil-plant systems, various N losses pathways, present status and most possible management options at the farm level for enhancing nitrogen use in crop production system.

A case study was undertaken to assess the risk of sewage-irrigated soils in relation to the transfer of trace elements to rice and wheat grain. For this purpose, peri-urban agricultural lands under the Keshopur Effluent Irrigation Scheme (KEIS) of Delhi were selected. These agricultural lands have been receiving irrigation through sewage effluents since 1979. Sewage effluent, groundwater, soil, and plant (rice and wheat grain) samples were collected with GPS coordinates from this peri-urban area. Under wheat crop, sewage irrigation for four decades resulted into a significant buildup of zinc (141 %), copper (219 %), iron (514 %), nickel (75.0 %), and lead (28.1 %) in sewage-irrigated soils over adjacent tube well water-irrigated ones. Under rice crop, there was also a significant buildup of phosphorus (339 %), sulfur (130 %), zinc (287 %), copper (352 %), iron (457 %), nickel (258 %), lead (136 %), and cadmium (147 %) in sewage-irrigated soils as compared to that of tube well water-irrigated soils. The values of hazard quotient (HQ) for intake of trace toxic elements by humans through consumption of rice and wheat grain grown on these sewage-irrigated soils were well within the safe permissible limit. The variation in Zn, Ni, and Cd content in wheat grain could be explained by solubility-free ion activity model (FIAM) to the extent of 50.1, 56.8, and 37.2 %, respectively. Corresponding values for rice grain were 49.9, 41.2, and 42.7 %, respectively. As high as 36.4 % variation in As content in rice grain could be explained by solubility-FIAM model. Toxic limit of extractable Cd and As in soil for rice in relation to soil properties and human health hazard associated with consumption of rice grain by humans was established. A similar exercise was also done in respect of Cd for wheat. The conceptual framework of fixing the toxic limit of extractable metals and metalloid in soils with respect to soil properties and human health hazard under the modeling framework was established.

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An experiment was conducted with aim to investigate the effect of sowing dates and irrigation regimes on wheat grain quality. There was four sowing dates [November 1(S1), November 16 (S2), December 1(S3) and December 16 (S4)], in main plots and four irrigation regimes [25% (I1), 50% (I2) and 75% (I3) maximum allowable depletion (MAD) of available soil moisture (ASM) and I4 – four critical growth stages in sub plots. The results revealed that hectolitre weight decreased from 80.2 and 81.4 kg hl-1 in S1 treatment to 78.3 and 79.4 kg hl-1 in S4 treatment and 79.9 and 81.5 kg hl-1 in I1 treatment to 79.0 and 79.9 kg hl-1 in I3 treatment in 2010-11 and 2011-12, respectively. Grain hardness outcome was ≥75 in 2010-11 while it was <75 in 2011-12 irrespective of sowing dates and irrigation regimes. The highest percentage of flour recovery obtained in S1 treatment (68.2 and 63.2%) and I1 treatment (68.0 and 62.8%) with lowest coarse bran. On average, dry gluten content increased by 16.5 and 7.1% in S4 over S1 treatment in 2010-11 and 2011-12, respectively. Grain protein content increased from 11.9 and 12.8% in S1 treatment to 12.6 and 13.8% in S4 treatment in respective seasons. The milling and technological properties in S2 and I2 treatment was at par with S1 and I2 treatment. Therefore, it may be inferred that optimum milling and technological properties of wheat grain can be maintained by sowing till mid-November and irrigation scheduling up to 50% depletion of ASM.