Abstract
Limited information exists on how tillage and nitrogen (N) fertilization affects small-scale variation in nitrogen use efficiency (NUE) and crop performance. In a two-year field study under temperate conditions, we investigated how tillage (NT, no-tillage; CT, conventional tillage) and N fertilization affected the small-scale variation in NUE and winter wheat performance (grain yield, Gw; grain protein concentration, GPC). A randomized complete block design with three replications was used. Within each tillage plot (12 × 35 m2), N rates (0, 50, 100, 150, 200, 250 kg N ha−1) were completely randomized within each of four groups of microplots (1.5 × 1.5 m2). Early-season soil mineral N (Nmin) was also monitored in both years. At rates < 150 kg N ha−1, NT was not competitive with CT in terms of Gw and NUE. Gw and aboveground plant N were not correlated with Nmin prior to application of N fertilizer. NT usually led to larger spatial heterogeneity of Nmin, Gw, and NUE. The small-scale variability of Gw, GPC, NUE, and N supply decreased with increasing N fertilization rates under both tillage systems. Significant increases in Gw and GPC were observed with increasing N rates, whereas NUE decreased slightly with increasing N rates in both NT and CT. The overall moderate spatial variation in Nmin, Gw, and NUE did not justify site-specific N fertilization in these small fields, with the exception of the stony within-plot positions, which were not responsive to rates of N > 50 kg N ha−1.
Highlights
Wheat is one of the world’s most important staple crops with forecast annual production of 757.4 million metric tons in 2019 contributing to global food security and providing 20% of total dietary calories and protein needs [1,2]
The results indicated that at low rates of N supply (Ns) fertilization, no-tillage (NT) showed a significantly lower nitrogen use efficiency (NUE) than conventional tillage (CT) in both years of this study
Given the increasing needs for N fertilizer inputs to manage yield improvements, more understanding of the interactions with N availability and any additional benefits associated with NT is required
Summary
Wheat is one of the world’s most important staple crops with forecast annual production of 757.4 million metric tons in 2019 contributing to global food security and providing 20% of total dietary calories and protein needs [1,2]. For an important food crop such as wheat, it is essential to increase the fertilizer nitrogen use efficiency in view of satisfying the growing demands and the decreased cropland [5,6]. Low soil nitrogen (N) availability is a common factor limiting the growth and crop production worldwide and the application of N fertilizer has become an important, cost-effective strategy used to increase crop yields in intensive agricultural systems [7]. Of the total fertilizer N applied, approximately half is consumed by the three most important cereals (rice, wheat, and maize) with 50-year (1961–2010) average application rates of 69, 51, and 77 (kg ha−1), respectively [9]. The average N uptake gaps, to achieve 80% of the full yield potential, are 87, 77, and 43 kg N ha−1 for wheat, barley, and maize, respectively
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