Alternatives for Nitrogen Diagnosis for Wheat with Different Yield Potentials in the Humid Pampas of Argentina

Abstract

A correct determination of nitrogen (N) fertilization thresholds in wheat that is based on objective yield produces efficient use of this nutrient. Nitrogen fertilization recommendations for traditional wheat require determination of nitrate (NO 3 − )-N availability at 60 cm deep at planting time. However, this methodology is complicated, expensive, and time-consuming; thus, the determination of NO 3 − -N level at a lesser depth and at a different time would be desirable. The goals of this work were to determine available N in soil thresholds for traditional and French germplasm wheats and the feasibility of diagnosing N requirements by measuring NO 3 − -N at 40 cm deep, at planting or tillering times, in the southeastern Pampas. The experiments were factorial combinations of N rates and fertilization times (planting and tillering) at different sites and years during 2002-2006. Nitrogen fertilization significantly increased grain yield and protein content. French varieties presented greater grain yield (23%), lower protein content (11%), and greater yield per N unit, indicating greater N-use efficiency (NUE) than traditional varieties. A similar relationship was determined between grain yield and available N at both sampling depths. This might be explained by the strong association between NO 3 − -N content at 60 and 40 cm deep at both sampling dates. Maximum yield and available N determined at 60 or 40 cm soil deep showed that thresholds were lower for tillering than for planting, regardless of the genotype (152 and 174 kg of available N, respectively). Available N thresholds for 95% of maximum yield were less at 0-40 cm deep than at 0-60 cm deep (10 and 14 kg N ha −1 for traditional and French genotypes, respectively). The results of this experiment suggest the possibility of diagnosing N requirements for wheat by measuring NO 3 − -N content at 40 cm deep, instead of the usual 60 cm, for both traditional and French genotypes.

Using Canopy Indices to Quantify the Economic Optimum Nitrogen Rate in Spring Wheat

“…In 2011 and Necochea, the greatest N response can be partially explained by low N0 3 --N and Nan levels observed at sowing, for one side, and for the high yield potential of the site (Table 1 and 2). Similar responses were determined by other authors in the SEB Barbieri et al, 2012;Reussi Calvo et al, 2013).…”

“…The worldwide fertilizer NUE for cereal production is approximately 33%, and the fertilizer N lost represents a value of $15.9 billion (USD) (Raun and Johnson, 1999). In Mollisols of the Pampas Argentina, the most extended methodology to diagnose N fertility for spring wheat (Triticum aestivum L.) is mainly based on the determination of soil nitrate N (NO 3 --N) content (0-60 cm depth) at sowing Barbieri et al, 2012;Reussi Calvo et al, 2013).…”

“…To use it, different N availability thresholds (soil + fertilizer) have been suggested, which varies according to the area, farming systems, and target yield (Barbieri et al, 2012;Garcia et al, 2010). However, the application of this diagnosis method does not consider the impact of input costs and their relation to the price of the product (input-output ratio).…”

Delineation of management zones to improve nitrogen management of wheat

“…In south-eastern Buenos Aires province, the benchmark or common N fertilizer rate (Nf) that most farmers use is Nf = CT À x, where Nf = N fertilizer, CT = critical threshold of N available at sowing (125 kg N ha À1 for yields <4500 kg ha À1 ; 170 kg N ha À1 for yields of about 6000-7000 kg ha À1 ) Barbieri et al, 2012) and x is the N-nitrates availability at 0-60 cm of sowing depth. The N fertilizer rates applied were a control (0 N), 125 À x (the traditional benchmark) and 170 À x.…”

Soybean and wheat response to lime in no-till Argentinean mollisols

“…In this region, crop production has been significantly increased in the last years as consequence of better management practices which included P and N fertilization and, occasionally, S fertilization. On the other hand, a reduction in soil organic matter (Sainz Rozas et al, 2011) and the large area under no-tillage has increased markedly the N deficiencies and crop response to this nutrient (Sainz Rozas et al, 2008;Velasco et al, 2012;Barbieri et al, 2012). Therefore, applied N rate to crops has been increased contributing to progressive soils acidification (Sainz Rozas et al, 2011).…”