Conservation tillage rotation enhanced soil structure and soil nutrients in long-term dryland agriculture

Abstract

Conservation tillage has been proposed as an effective way to conserve soil water in dryland agriculture. However, long-term continuous mono-tillage including conservational and conventional tillage has been proved to have limited improvements or some defects on soil structure and nutrients enhancement. Combining different tillage practices in a rational rotation that adapts to the cropping system may optimize the advantages and improve the potentials of mono-tillage practices. Soil porosity, aggregates, water, organic carbon, nitrogen and crop yield were investigated in a ten-year (2007–2016) long-term conventional with conservation tillage rotation experiment which contained four tillage systems, NT (no-tillage), ST (subsoiling), CT (conventional tillage), and NCS rotation (no-tillage, conventional tillage and subsoiling rotated annually) in a dryland field to assess the soil pore system, aggregates, nutrients content and productivity. Compared with three mono-tillage systems (NT, ST and CT), the NCS rotation significantly decreased soil bulk density by 3.8–8.4 % and increased soil porosity by 3.2–6.7 % (P < 0.05) after ten years. NCS rotation increased soil capillary porosity by 9.7–36.3 %, reduced inactive porosity by 4–8.1 % when compared to continuous mono-tillage (NT, ST and CT), optimized soil porosity distribution at 0−60 cm soil depth till the tenth year. Meanwhile, compared with mono-tillage, NCS rotation improved soil macroaggregates content (0.25–5 mm) by 35.2–46.4 % and resulted in 40.3–113 % higher macroaggregates content than ten years before at 0−40 cm soil depth (P < 0.05). As the experiment continues, soil organic carbon (SOC) and nitrogen (TN) at different tillage systems accumulated at rates of 1.65−2.01 Mg ha−1 year−1 and 0.14−0.21 Mg ha−1 year−1, respectively, NCS rotation resulted in the highest soil nutrients accumulation (SOC: 57.98 Mg ha−1, TN: 6.40 Mg ha−1), better soil nutrients distribution and suitable C/N (9.01) for crop growth and soil enhancement. Additionally, NCS rotation conserved more soil water in fallow period (394 mm) and during crop growth season (winter wheat: 352 mm, spring maize: 384 mm), produced higher winter wheat (5169 kg ha−1) and spring maize yield (8251 kg ha−1). The long-term rotational research showed that NCS rotation optimized soil structure (soil porosity, soil aggregates) and enhanced soil nutrients (SOC, TN), provided better soil conditions for crop production in dryland rain-fed farming agriculture.