Use of Nitrogen Fertilizer in a Targeted Way to Improve Grain Yield, Quality, and Nitrogen Use Efficiency

Abstract

Nitrogen fertilizer management in rainfed Mediterranean environments can be nancially risky because of the strong interaction between N and water availability on yield. is study was conducted to investigate whether the use of split-applications of N fertilizer that targeted speci c growth stages could improve grain yield, grain protein concentration (GPC), and nitrogen use e ciency (NUE) of dryland wheat (Triticum aestivum L.). Experiments with 7 N-application timings, two N-rates, and two wheat varieties were conducted at two sites over two seasons. Despite the seasonal rainfall in both years being below the historic averages, delayed or split N applications were able to signi cantly increase grain yield (2.50 vs. 2.25 t ha -1 ), GPC (14.0 vs. 12.4%), N uptake (111.2 vs. 101.2 kg ha -1 ), N harvest index (70.7 vs. 61.7%), agronomic e ciency (4.6 vs. 1.7 kg kg -1 ), and apparent recovery (59.3 vs. 44.6%) compared with N applied only at sowing. No single N treatment was able to consistently produce the highest yield, GPC or NUE across the N rates, locations, and years because of the in uence of timing and amount of rainfall during the season. Compared with applying all the N at sowing a targeted use of N, using split/delayed N applications at speci c growth stages to manage canopy development in response to the seasonal pattern of rainfall, increased yield, quality, and NUE, even in years with below average rainfall, thus lessening exposure to nancial risk with rainfed wheat in dry years.

Can additional N fertiliser ameliorate the elevated CO2‐induced depression in grain and tissue N concentrations of wheat on a high soil N background?

“…Such an effect of N treatment on grain [N], albeit small, was observed in our study, even though N application that targets grain protein would ideally be applied later in the season (Hooper et al, 2015). However, there was no interaction between N application Grain N in cereals is supplied by root uptake during grain filling or by translocation of N previously accumulated in the biomass.…”

“…The N source and management methods to meet additional crop demands for N in a high‐[CO 2 ] atmosphere need to be carefully considered (Bloom, ; Carlisle, Myers, Raboy, & Bloom, ), because N fertiliser can have large negative impacts on the environment (Robertson & Vitousek, ) and already constitutes a relatively costly and risky farm input in these cropping systems primarily limited by low and unreliable rainfall (Angus, ). Probably even more important than such quantitative considerations are qualitative aspects of nitrogen management (Bloom, ), such as selection of nitrogen form to promote uptake of reduced nitrogen so that biochemical limitations to nitrate assimilation can be circumvented (Bloom et al., ; Carlisle et al., ), or appropriate timing of N applications to target grain N (Hooper et al., ).…”

“…This would imply that insufficient soil N supply is not the only mechanism contributing to decreased [N]. Recent meta-analyses suggested that high soil N supply cannot fully restore, but at best only moderates the negative effect of e[CO 2 ] on tissue and grain [N] Wang et al, 2013 In cereals such as wheat, N requirement for growth and grain yield is generally satisfied before that of increased grain protein, so that grain protein concentration can be increased by N application above the level needed for growth and yield responses (Fowler, 2003;Hooper, Zhou, Coventry, & McDonald, 2015). To understand whether N supply beyond the demand for growth and yield can restore grain protein under e[CO 2 ] to that achieved under ambient CO 2 , it would be important to investigate an agro-ecosystem that has adequate N supply for growth and yield.…”

Optimal Supply of Water and Nitrogen Improves Grain Yield, Water Use Efficiency and Crop Nitrogen Recovery in Wheat

“…Moreover, application of N during earlier growth stages can result in range of possible losses due to its greater immobilization, leaching, and clay fixation. The increase in grain yield of wheat with the three splits of N fertilizer may also be related to improved photosynthesis and grain weight (Table 4) resulting from enhanced availability for uptake (Table 6) throughout the growing season (Hooper et al, 2015) and also less losses of N from leaching.…”

Biochar Reduced Nitrous Oxide and Carbon Dioxide Emissions from Soil with Different Water and Temperature Cycles

“…To reduce agricultural impact on the environment, GHG emissions need to be reduced and N fertilizer effi ciency needs to be enhanced Mohammed et al, 2016). Traditional approaches to reduce GHG emissions include: (i) reducing the tillage intensity, (ii) reducing N fertilizer additions, (iii) adopting techniques, such as cover crops, that improve nutrient recycling; and (iv) splitting the N application (Clay et al, 2012(Clay et al, , 2015Reese et al, 2014;Kovács et al, 2015;Hooper et al, 2015). Unfortunately, some of techniques may increase labor and production costs while adversely eff ecting yield.…”