Impact of cropping systems on soil quality

Abstract

The agricultural intensification process implemented during the last 20 years consisted of replacing a crop-pasture rotation system with a continuous no-till cropping system that affected the functional properties of the soil in the medium term. The hypothesis of this study was that the annual cropping intensification process could be characterized, at the commercial level, by soil property indicators that capture changes in the pathway of cropping systems (CSs) in the medium term. The objectives were: i) to identify CSs based on land use; and ii) to characterize soil properties associated with different CSs. Based on this, a database was built with the land use description from 2014 to 2020 of 45 farms belonging to farmers associated with FUCREA and AUSID. A Principal Component Analysis (PCA) was performed with 14 land use indicators to select those that best summarized all the information. The selected indicators were pasture-crop ratio (PCR), soybean frequency during the summer annual cropping phase (SSbCF), intensification of annual cropping phase index (IAI), and intensity of soil use index (ISI). By performing a Cluster Analysis with these indicators, the following CSs were identified: pasture-crop rotation (ROT-PC), continuous cropping with high frequency of C4 photosynthesis species (CC_Corn), and continuous cropping with high frequency of soybean (CC_Soybean). Based on the identified CS, 64 representative sites were selected within a 60 km radius from the coordinates −33.17 S and −57.80 W, Uruguay's most influential annual cropping area, assessing 46 soil properties sensitive to changes in their management in the medium term and capable of affecting productivity. A PCA was used to select the properties that best summarized the information. A Linear Discriminant Analysis (LDA) with the selected variables and the identified CS groups determined a loss in soil fertility (organic carbon and electrical conductivity) and nutrient availability (potassium), which is related to CS diversification (CC_Soybean> CC_Corn>ROT-PC).