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Blanket fertilizer nitrogen (N) recommendations for large irrigated wheat tracts lead to low N-use efficiency due to field-to-field variability in soil N supply and seasonal variability in yield. To achieve high N use efficiency, a site-specific N management strategy using GreenSeeker™ optical sensor was evaluated. We conducted seven field experiments(More)
 A sandy loam was incubated under floodwater in the laboratory either in the dark or in the light (7 h day, 20  °C; 17 h night, 15  °C) and with four N sources [control, ammonium carbonate [(NH4)2CO3], ammonium chloride (NH4Cl), potassium nitrate (KNO3)]. In the dark, floodwater pH rose steadily from 6.4 to about 7.5 over 60 days in the control, KNO3 and(More)
Fertilizer nitrogen (N) is one of the major inputs in rice–wheat production systems in South Asia. As fertilizer N has generally been managed following blanket recommendations consisting of two or three split applications of preset rates of the total amount of N, improvement in N use efficiency could not be achieved beyond a limit. Feeding crop N needs is(More)
Poultry litter (PL) is an important nutrient source; however, no information is available regarding its value in supplying N and P in rice–wheat (RW) production. A three-year field study was conducted at Ludhiana, Punjab, India on a loamy sand soil to identify optimum combination of PL and N and P fertilizers for a sustainable RW production. The litter was(More)
Neem coated urea (NCU) applied to rice can result in high N use efficiency as it contains nitrification inhibition properties. Field experiments were conducted for three years (2005–2007) at Ludhiana (sandy loam soil) and Gurdaspur (clay loam soil) for evaluating the relative performance of NCU vis-à-vis ordinary urea as a source of N for transplanted(More)
The present investigation was undertaken to elucidate the effect of floodwater algae and green manure on floodwater pH and depth of aerobic soil layer which are mainly responsible for the nitrogen losses in lowland rice production systems. The study was conducted in an environmental chamber using a sandy loam soil. Cylindrical plastic bottles 7 cm in(More)
 The effects of floodwater algae and green manure on transformations of 15N-urea were studied in columns of a sandy loam soil in a growth chamber. The columns were flooded and either kept in the light, to allow algal growth, or in the dark (control) for 17 days before adding the labelled urea. Changes in urea-, NO3 –- and NH4 +-N levels and the pH of the(More)
In the Indo-Gangetic plain in South Asia, fertilizer nitrogen (N) application to irrigated wheat in two split doses at planting and at crown root initiation (CRI) stages of the crop is the general recommendation. Farmers have a tendency to apply another dose of N at maximum tillering (MT) stage to avoid the risk of N deficiency. However, appropriate(More)
Algal N labelled with 15N added to a flooded soil in laboratory columns without plants was studied to determine the changes over time in the fate of N assimilated by algae and to study how its fate is affected by (a) exclusion of light simulating complete closure of the rice canopy, and (b) addition of fertilizer-NH4 *. In the light but with no added(More)
Application of fertilizer N doses to rice (Oryza sativa L.) whenever leaf greenness as measured by chlorophyll meter (SPAD) and LCC falls below a fixed threshold is being extensively used for site-specific management of fertilizer N. As fixed threshold greenness varies with regions, rice cultivars and seasons, a dynamic threshold greenness concept in the(More)