Time and source of nitrogen application in rice and wheat

Abstract

The results of four field experiments conducted for 2 or 3 years on two soils, loamy sand (Typic Ustipsamments) and silty clay loam (Natric Ustochrept) showed that in rice, application of N in three equal amounts was more efficient than one or two applications, irrespective of source of N and type of soil. The results further showed that application of the first dose of N 7 days after transplanting rice was more beneficial than its application at transplanting. Calcium ammonium nitrate was significantly inferior to urea and/or ammonium sulphate for rice in both soils. There were no significant differences in wheat yield, N concentration or uptake due to time and source of N application.

Assessment of the nitrogen management strategy using an optical sensor for irrigated wheat

“…Thus, different GreenSeeker optical sensorbased fertilizer N management scenarios in wheat as listed in Tables 4, 5, 6, and 7 were evaluated vis-à-vis blanket recommendations of 120 and 150 kg N ha -1 . Application of fertilizer N in two equal split doses-half at sowing and half at crown root initiation stage (along with first irrigation) has been found beneficial in increasing grain yield and N uptake of wheat, and it is a general recommendation for wheat over a vast area in the IndoGangetic Plain (Meelu et al 1987). Nitrogen uptake of irrigated wheat proceeds very slowly until tillering begins, and N flux (kg N ha −1 day −1 ) increases to a maximum around Feekes 6 stage (Doerge et al 1991).…”

“…The second dose coincides with first irrigation event around 21 days after planting. This being a blanket recommendation for the region consists of applying N doses at planting and crown root initiation stage (Meelu et al 1987) high enough to meet the crop requirement as well as to compensate the losses of N via ammonia volatilization, denitrification and leaching (Bijay-Singh and Yadvinder-Singh 2003). To achieve high fertilizer use efficiency, prescriptive N doses at planting and crown root initiation stage (or first irrigation stage) can be moderately reduced provided N needs of the crop taking into account the field-to-field and temporal variability are worked out using a suitable criteria to apply a corrective fertilizer dose coinciding with second or third irrigation event.…”

Need based nitrogen management using the chlorophyll meter and leaf colour chart in rice and wheat in South Asia: a review

“…Generally N is applied to wheat in two equal split doses-basal at land preparation and top dressing at crown root initiation (Meelu et al 1987). Suitable criteria were lacking to determine whether or not N application at maximum tillering is needed.…”

Nitrogen losses and fertilizer N use efficiency in irrigated porous soils

“…In humid regions or in wetland rice ecosystems, soils are less likely to contain or retain residual NO3. Therefore, fertilizer N needs should be estimated by multiplying the expected yield by a factor that can be adjusted to take into account the economic optimum as well as such factors as expected mineralization and use of manures and legumes [ 15,22,56].…”

“…The 1000-grain weight was only slightly influenced by N fertilization. Since both [30] panicle density and spikelet number are known to be determined within 70 days after transplanting of rice, N uptake during this period was found to be critical to achieve a maximum grain yield response to applied N. Thus application of N in three equal doses at transplanting, tillering and panicle initiation proved more efficient in terms of grain yield than in one or two doses irrespective of source of N [15,56]. Obviously fertilizer applied at a time when crop needs are high will lead to reduced losses of applied N from the soil-plant system.…”