Abstract
Adequate fertilization strategies are paramount to fulfill increasing demands for food, feed and fiber while reducing environmental impacts. However, their optimization under Mediterranean no-till systems has received little attention. The objective of this work was to assess winter cereal yield and water and N use efficiencies in a rainfed semiarid Mediterranean climate under (i) a range of pre-plant fertilizers [control without N fertilizer (0 N), and the following at 75 kg N ha−1: mineral N (MIN), swine slurry (SS), poultry manure (PM), and compost (COM)], (ii) fertilizer incorporation: no-tillage without incorporating (NT) or incorporation with a vibrocultivator (INC) and (iii) application of urea-ammonium nitrate solution (UAN) as top-dress as a control without UAN (UAN-) or 50 kg N ha−1 (UAN+). The experiment covered six cropping seasons (2012–2019).Pre-plant applications had similar responses in crop yield, biomass, N uptake, grain N, water-use efficiency for biomass (WUEb), and water-use efficiency for yield (WUEy) but were greater than 0 N. The lack of differences between pre-plant fertilizers would be explained by the high amount of residual N and the mineralized N during the crop cycle. Top-dress UAN increased WUEy and crop yield in all the cropping seasons by an average of 587 kg grain ha−1, which represented 18 % of the total annual production. Averaged across variables and the growing seasons, INC reduced soil water content and WUEb by 10 % (from 24.3 to 21.8 kg ha−1 mm−1). Also, INC reduced grain yield by 9% (from 3799 to 3450 kg ha−1) by reducing the number of spikes m-2 produced, pointing out that INC resulted in water deficit during the early reproductive period of the crop. While INC is often consider a best management practice to reduce NH3 volatilization losses from broadcast fertilizer applications, the results demonstrate that in rainfed Mediterranean agroecosystems water is more limiting than the N that could be potentially lost by volatilization.
Highlights
The sustainable use of N fertilizers is key for maintaining a growing population while avoiding losses of reactive N to the environment such as nitrate leaching, ammonia volatilization and nitrous oxide emission to the atmosphere (Mosier, 2002)
While incorporation with a vibroculti vator (INC) is often consider a best management practice to reduce NH3 volatilization losses from broadcast fertilizer applications, the results demonstrate that in rainfed Mediterranean agroecosystems water is more limiting than the N that could be potentially lost by volatilization
The experimental design consisted of the combination of (i) a range of pre-plant fertilizers [control without N fertilizer (0 N), and the following at 75 kg N ha− 1: mineral N (MIN), swine slurry (SS), poultry manure (PM), and compost (COM)], (ii) fertilizer incorporation: no-tillage without incorporating (NT) or incorporation with a 5-cm depth pass of a vibrocultivator (INC) and (iii) application of urea-ammonium nitrate solution (UAN) as top-dress at the beginning of tillering as a control without UAN (UAN-) or 50 kg N ha− 1 (UAN+) arranged in a split-strip block design with three blocks
Summary
The sustainable use of N fertilizers is key for maintaining a growing population while avoiding losses of reactive N to the environment such as nitrate leaching, ammonia volatilization and nitrous oxide emission to the atmosphere (Mosier, 2002). N fertilization represents a major cost for field crop production Maresma et al, 2016) and its management is key in rainfed areas, where crop growth, N mineraliza tion dynamics, N uptake and N losses strongly depend on the magnitude and distribution of precipitation. Rainfed agriculture is the dominant crop and forage production system throughout the world with around 80 % of the global surface (Hatfield et al, 2001; Rockstrom and Karlberg, 2009). A proper nitrogen rate is difficult to estimate in many rainfed areas due to precipitation unpredictability. Low productivity in arid and semiarid rainfed areas forced farmers to diversify their sources of revenue by focusing on animal production. Traditional live stock farms have undergone drastic intensification leading to a high concentration of animals in rural areas (Sanchez-Bascones et al, 2019)
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