Lower soil chemical quality of pomelo orchards compared with that of paddy and vegetable fields in acidic red soil hilly regions of southern China

Abstract

Sustainable land management is considered an effective measure to ensure national food security by matching improved soil quality with enhanced crop productivity. The objectives of the present study were to evaluate soil quality status among paddy fields, vegetable fields, and pomelo orchards managed by continuous cropping systems, to establish a minimum data set (MDS) and recommend fertilization strategies to enhance productivity in acidic red soil hilly regions. The soil quality index (SQI) was calculated using the total data set (TDS) and MDS as indicator selection methods. A total of 51, 32, 44 soil samples (0–20 cm) were collected from different cropping systems in paddy fields, vegetable fields, and pomelo orchards, respectively. Eleven soil properties (geographical indicator (altitude) and 10 chemical parameters) were measured to evaluate soil quality of acidic red soil hilly regions in Pinghe County, Fujian province, southern China. The results showed significant differences in soil quality indicators between paddy fields, vegetable fields, and pomelo orchards, and altitude, total N, hydrolysable nitrogen (Avail-N), exchangeable calcium (Avail-Ca), and available zinc (Avail-Zn) were adopted as indicators in the MDS using principal component analysis (PCA). After scoring and weighting the selected indicators, the mean SQI scores of paddy field, vegetable field, and pomelo orchard soils were 0.267, 0.282, and 0.236 for TDS, respectively, and the SQI scores were 0.233, 0.256, and 0.166 for MDS. A significant positive correlation was observed between SQI and crop yield using both the TDS and MDS methods, indicating that the MDS method adequately represents the TDS method (R2 = 0.6839) for evaluation of the effects of farming production practices on soil quality. Overall, the unbalanced soil quality indicators, including rich in total N, organic matter and Avail-P, and deficient in Avail-N, Avail-K, Avail-Ca, Avail-Mg, Avail-Zn, and Avail-B, were implicated as the main limiting factors for crop production in the studied regions. Compared with paddy and vegetable fields, the lower total N and Avail-N status at higher altitudes were considered as the major factors limiting pomelo productivity. Therefore, there is a great potential for increasing pomelo productivity by improving soil quality with integrated nutrient management in acidic red soil hilly regions.