Examining crop root apparatus traits in a maize-soybean-winter wheat rotation under conservation agriculture management

Abstract

Conservation agriculture (CA) is a farming system that promotes minimum soil disturbance, maintenance of a permanent soil cover, and diversification of plant species and was introduced also in the Veneto region of north east Italy. CA is not always viewed as a win-win solution for sustainable production because of the increase in soil strength and compaction that may negatively impact root growth and crop production. In this study, our aim was to analyse root length density (RLD), mean diameter (MD), and root distribution to 90 cm at the flowering stage, following a maize-soybean-winter wheat rotation cycle under CA and conventional tillage (CV) at four farms. Root traits were related to soil physical properties (gravimetric water content, bulk density, and electrical resistivity) and to existent critical limits of penetration resistance (PR), and the degree of compactness (DC). CA management was not detrimental to root development and positively affected the RLD of maize (+70 %), soybean (+121 %) and winter wheat (+20 %) at 0–10 cm most likely because of increased nutrient availability. No specific physical limitations of soil were highlighted for the crop root apparatus in three (silty soils) out of four farms. Farm 3 (sandy soil) with a hardpan below 35 cm caused lateral root development in winter wheat, but not in maize or soybean. The yield gap between CA and CV (-3.9 t ha−1 for maize, -0.4 t ha-1 for soybean and -0.7 t ha-1 for winter wheat) may have been due to other agronomic factors, notably insufficient weed control in CA. Critical limits of PR (2 or 33.5 MPa) and DC (87 %) did not seemed to impair root traits, irrespective of the tillage system, suggesting that further studies on soil-specific mechanisms between soil compaction and root apparatus are warranted.