Significant soil degradation is associated with intensive vegetable cropping in a subtropical area: a case study in southwestern China

Ming Lu,Dave R Chadwick,Xinping Chen,Dunyi Liu,David S Powlson,Shengbi Long,Yi Liang

doi:10.5194/soil-7-333-2021

Ming Lu, Dave R Chadwick + Show 5 more

Open Access

https://doi.org/10.5194/soil-7-333-2021

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Abstract

Abstract. Within the context of sustainable development, soil degradation driven by land use change is considered a serious global problem, but the conversion from growing cereals to vegetables is a change that has received limited attention, especially in subtropical regions. Here, we studied the effects of the conversion from paddy rice to an oilseed rape rotation to vegetable production in southwestern China on soil organic carbon (SOC), total nitrogen (TN), the C/N ratio, pH, phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) based on face-to-face farmer surveys and soil analysis. In the vegetable cropping system, fertilizer application often exceeds the crop demand or levels recommended by the local extension service several times over. Thus, the crop use efficiency of N, P, K, Ca, and Mg was only 26 %, 8 %, 56 %, 23 %, and 28 %, respectively. In the vegetable cropping system studied, SOC, C stock, TN, and N stock were decreased significantly due to low organic inputs from crop residues and high tillage frequency. Furthermore, the soil C/N ratio decreased slightly; available P (AP) in the topsoil increased by 1.92 mg kg−1 for every 100 kg ha−1 of P surplus, and the critical levels of AP and CaCl2-soluble P in P leaching were 104 and 0.80 mg P kg−1. Besides, compared to the current paddy–rape rotation system, a clear trend of soil acidification was observed in the vegetable fields. However, increasing the contents of soil Ca and Mg significantly alleviated topsoil acidification, with the effect increasing over time. Given our findings, the potential benefits of conservation agricultural practices, integrated soil–crop system management strategies, and agricultural technology services for recovering the degraded soil and improving the vegetable productivity are discussed here.

Highlights

Land use changes are an important anthropogenic perturbation that can cause soil degradation (Lal, 2004, 2015), but the impacts of land conversion from growing cereals to vegetables have received little attention
The objectives of this study were to assess the impacts of the land use conversion from a paddy–rape rotation to vegetable production on soil pH, soil organic carbon (SOC), total nitrogen (TN), the soil C/N ratio, available P (AP), CaCl2-soluble P (CaCl2-P), and available base cations (K, Ca, and Mg)
Intensive openfield vegetable production in southwestern China can result in significant soil degradation and potential environmental pollution after conversion from paddy rice to an oilseed rape rotation

Summary

Introduction

Land use changes are an important anthropogenic perturbation that can cause soil degradation (Lal, 2004, 2015), but the impacts of land conversion from growing cereals to vegetables have received little attention. From 1997to 2017, total vegetable production increased by 98 % worldwide, and the area harvested increased by 59 % (FAO, 2017). These increases were driven by economic growth and an increased demand for vegetables associated with a raised awareness of their health benefits (Yan et al, 2012). In contrast to cereal crops, vegetable production requires more intensive management, including higher tillage frequencies and fertilization rates, and higher nutrient and water inputs due to the shallow root systems of most vegetable species (Wang et al, 2018a, b; Yan et al, 2013; Zhang et al, 2017). Overuse or misuse of fertilizers in vegetable fields is a long-standing problem across the world (Conley et al, 2009)

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