Rotational benefit of pulse crop with no-till increase over time in a semiarid climate

Water deficit is the major constraint to crop production in dry temperate climates and no-till (NT) has been widely recommended to increase water conservation, crop yields, and soil organic carbon (SOC) content. In this study, tillage practice [conventional tillage (CT), minimum tillage (MT), NT and annually alternating tillage with NT (NT/MT)]] and crop rotation [fallow-wheat (Triticum aestivum L.; FW), continuous wheat (CW), and wheat-pulse (WP) rotation] effects were investigated in a long-term experiment over three decades. Although NT increased soil water conservation and water use efficiency (WUE) compared to CT and MT, wheat yields were not higher for NT during the first 13 years when nitrogen (N) fertilizer was broadcast in the soil. After 1996, when N fertilizer was side-banded during seeding, CW-NT had 6% higher yields than CW-MT although not significant. The mean yield of pulse crops was 14 % higher for NT than MT, where the greatest yield benefit was found in warmer and drier years so NT is also adaptation to weather variability. The yield advantage of wheat after pulse in WP compared to CW increased by 41 kg ha⁻¹ yr⁻¹ (P < 0.001), indicating that the benefits of pulse crop on wheat production increases with time. Annual grain N uptake was greater in WP than CW or FW and greater for NT than MT for WP. The biennial tillage in CW-NT/MT benefitted the wheat yield in the following NT year so that it was greater than those of both CW-MT and CW-NT in those years. The rankings of SOC stock to 15 cm or 30 cm were generally the same as to 7.5 cm but differences were only significant to 15 cm in some samplings and only a trend (P < 0.10) was detected to 30 cm after 29 years. Unexpectedly, the CW-NT/MT had the highest SOC stocks and such regular periodic tillage warrants further investigation. The pulse-wheat rotation under NT was the best cropping system for achieving a combination of efficient use of fertilizer N and high annual crop yield and quality, for which the benefit of pulse in rotation increases over time.