Nitrogen balance in organic horticultural rotations
Organic agriculture (OA) is a more sustainable farming approach than conventional agriculture to maintain ecosystem services and biodiversity. The main challenge of OA is to improve nutrient management in order to increase yields and reduce the risk of N losses. With this aim, a three-year field organic crop rotation with rye and vetch as green manure over the autumn/winter, followed by potato and lettuce (2012), Swiss chard and turnip (2013), and Portuguese cabbage and carrot (2014), was arranged as a randomized block design. The objective was to assess crop growth, crop nutrient uptake, and N mineralization determined by field incubation, in response to soil amendment with green manure (GM), GM with 20 and 40 t ha‑1 farmyard manure (FYM) compost (C20 and C40) and GM with 1 and 2 t ha‑1 of immature commercial organic fertilizer (CF1 and CF2). The difference between supplied nutrients (P, K, Ca and Mg) through soil organic amendments and nutrient uptake by organic horticultural crops was positive for C20 and C40, whereas the K, Ca and Mg balance was negative for GM, CF1 and CF2. The N balance was positive for all treatments except for GM. However, daily N mineralization for CF1 and CF2 occurred mostly during the first seven days after soil organic amendment with this fertilizer, increasing the risk of N losses. In contrast, the highest value of daily N mineralization for C20 and C40 occurred during the period of higher crop N demand, contributing to improve the synchronization between N mineralization and crop N demand and, consequently, improving the apparent N recovery efficiency during crop rotation. Therefore, the application of FYM compost with green manure contributed to build-up soil fertility, reducing N leaching impact.
Pinto, R., Brito, L.M., Mourão, I. and Coutinho, J. (2020). Nitrogen balance in organic horticultural rotations. Acta Hortic. 1286, 127-134
apparent N recovery efficiency, compost, field incubation, nutrient balance, organic agriculture