Nutrients accumulation in black oat (Avena strigosa) and pearl millet (Pennicetum glaucum) after application of herbicides glyphosate or glufosinate-ammonium

Abstract

Cover crops used in conservative cropping systems can accumulate large amounts of nutrients, reducing nutrient losses from the soil-plant system and improving the nutrient use efficiency in crops. However, recent researches demonstrated that herbicides used to kill cover crop could decrease N status in the straw, reducing the nutrient availability to the cash crop. In this context, the aim of this work was to investigate the effect of glyphosate or glufosinate-ammonium application in K, P, Ca, Mg, S and C status in plant´s tissues of black oat (Avena strigosa) and peal millet (Pennicetum glaucum) desiccated with herbicides. An experiment was carried out under greenhouse conditions using a factorial design 2x3. The evaluated factors were cover crop (black oat or peal millet) and cover crop management (1-Control- mechanical cut, without herbicide application; 2-Glyphosate- cover crop desiccation with glyphosate; 3-Glufosinate- cover crop dessication with ammonium-glufosinate). Dry mass production, nutrients accumulation in plants part and entire plants and the nutrient´s utilization efficiencies were determined. The nutrients accumulation in plants was not reduced by herbicides; however, a lower dry matter and C accumulation was observed after herbicides application. Glyphosate increased K, P, S and C remobilization from leaves to stalks, but glufosinate did not affect it, suggestion a lower effect of this herbicide in nutrients availability to cash crop. Herbicides did not affect K, P, Ca, Mg and S losses from plants, thus the total amount of these nutrients in the system should be not affected by glyphosate or ammonium glufosinate utilization. However, since glyphosate changes these nutrients distribution among plant´s parts, increasing nutrients in the stalks and reducing nutrients in the leaves of pearl millet, it may affect nutrient availability to cash crops, since leaves mineralization is faster than stalks mineralization on soil. In this sense, the herbicide application is a practice that should be considered for prediction of nutrients availability in soil-plant systems, aiming improve the nutrient´s use efficiency.