Soil Chemical Properties and Yield of Onion Crops Grown for Eight Years under No-Tillage System with Cover Crops

The use of cover crops in no-tillage systems can change soil chemical properties and crop yield over time. Studies using cover crops without the application of pesticides and soluble mineral fertilizers in no-tillage systems are important to reduce production costs, the need for mechanization, and to improve nutrient cycling and crop yield. The study aimed to evaluate how the use of different cover crops and the amount of dry matter produced by such species affect soil chemical properties and onion yield. Onion crops were grown for eight years without the use of pesticides and soluble mineral fertilizers in no-tillage system. The experiment was conducted from 2009 to 2016 in Ituporanga, state of Santa Catarina (SC), Brazil. The following treatments were used: barley (2010)/black oat, rye, oilseed radish, oilseed radish + rye, and oilseed radish + barley or black oat, and a control (consisting of weed species). A randomized block experimental design was used with eight replications. Plants from each treatment were collected 100 days after sowing in plot areas of 0.75 m2 to determine dry matter yield. The cover crops were desiccated and the onion seedlings were transplanted in July. The onion crops were harvested every November to evaluate yield. Soil samples were collected at depths of 0-10 and 10-20 cm after the onion harvest to evaluate soil chemical properties. The onion crop and residue deposition of single or intercropped black oat, rye, and oilseed radish improved and maintained soil chemical properties. The lower dry matter yield of cover crops found in the control treatment resulted in lower onion yields over the years. Cover crops combined with soil tillage limited to the planting rows increased total onion yields and yield of larger-sized onions as the system stabilized over time.