Conservation tillage and optimized fertilization reduce winter runoff losses of nitrogen and phosphorus from farmland in the Chaohu Lake region, China

In order to test the efficacy of conservation tillage and optimized fertilization on reducing N and P runoff losses, a 4-year (2007-2011) runoff plot experiment was conducted in the Chaohu Lake region, East China. There were four treatments including: (1) conventional tillage (CT, basal fertilization without mulch), (2) conventional tillage with straw mulching (CTS), (3) optimized fertilization (OPF, split applications) and (4) no-tillage with straw mulching plus optimized fertilization (NTS + OPF). Results showed that CTS and NTS + OPF exhibited significant reduction of seasonal runoff and soil losses compared with CT (P < 0.05). OPF decreased runoff by 6-10 and soil loss by 9-27 % in the various years, but differences were not always statistically significant. Interestingly, winter wheat and rapeseed yields were on average higher in the conservation tillage and optimized fertilization treatment than in the CT treatment. Compared with CT, CTS reduced N losses by 14-25 %, OPF by 12-21 % and NTS + OPF 20-28 %. Similarly, CTS reduced P losses by 20-32 %, OPF by 11-21 % and NTS + OPF by 23-30 %. NTS + OPF was the most effective treatment for reducing nutrient losses. The reduction of runoff volume was mainly responsible for the decreased nutrient losses. Our findings indicates that conservation tillage and optimized fertilization may reduce N and P losses via runoff while maintaining or enhancing crop yields during the winter-crop growing seasons in the Chaohu Lake region.

为了测试保护性耕作和优化施肥对减少氮、磷径流流失的效果，在中国东部巢湖地区进行了一项为期4年（2007 - 2011年）的径流小区试验。试验设置了4种处理方式，包括：（1）传统耕作（CT，基肥，无覆盖）；（2）传统耕作加秸秆覆盖（CTS）；（3）优化施肥（OPF，分次施肥）；（4）免耕加秸秆覆盖及优化施肥（NTS + OPF）。结果表明，与CT相比，CTS和NTS + OPF在季节性径流和土壤流失方面显著减少（P < 0.05）。在不同年份，OPF使径流量减少6 - 10%，土壤流失量减少9 - 27%，但差异并非总是具有统计学意义。有趣的是，在保护性耕作和优化施肥处理下，冬小麦和油菜籽的产量平均高于CT处理。与CT相比，CTS使氮流失量减少14 - 25%，OPF减少12 - 21%，NTS + OPF减少20 - 28%。同样，CTS使磷流失量减少20 - 32%，OPF减少11 - 21%，NTS + OPF减少23 - 30%。NTS + OPF是减少养分流失最有效的处理方式。径流量的减少是养分流失降低的主要原因。我们的研究结果表明，在巢湖地区冬作物生长季节，保护性耕作和优化施肥可通过减少径流来降低氮、磷流失，同时维持或提高作物产量。