Rainfed Wheat and Soybean Productivity in a Long‐Term Tillage Experiment in Central Italy

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Abstract
Tillage plays a key role in cropping system sustainability due to its impact on soil properties, crop yields, economic returns, labor, and energy requirements. The objective of our research was to compare the effects of no‐tillage (NT) and conventional tillage (CT) on durum wheat (Triticum durumDesf.) and soybean [Glycine max(L.) Merr.] productivity in a long‐term, 2‐yr rotation field experiment initiated in 1986 under a Mediterranean climate. The 16‐yr (1990–2005) average grain yield for NT wheat was 8.9% lower than that for CT wheat (3.97 vs. 4.36 Mg ha−1). Differences between tillage systems were significant in 6 out of the 16 seasons and were small when planting was early, weed control was good, and rainfall deficit occurred during the grain filling period. The 16‐yr average grain yield for soybean was significantly lower under NT than under CT (2.60 vs. 3.08 Mg ha−1) but differences between tillage systems were small and not significant in 12 out of the 16 seasons. In comparison to wheat, NT soybean had higher weed pressure. Nitrogen concentrations in wheat and soybean were little affected by tillage. Phosphorus concentrations in wheat grain and straw were generally higher under NT, while differences in soybean tissue P due to tillage were negligible.