Nutrient balance and soil changes in plastic greenhouse vegetable production

Nutrient surplus in intense production system such as plastic greenhouse vegetable production (PGVP) may affects soil degradation and further influences sustainable utilization. In this study, we analyzed nutrient balance of nitrogen (N), phosphorous (P) and potassium (K) in PGVP and measured soil fertility properties, pH and electrical conductivity (EC) in the North, the Middle and the South of Shaanxi Province, northwestern China. Considerable nutrient surplus was found in PGVP systems, and the average nutrient balance of N, P and K were 1407.0, 682.9 and 1169.1 kg ha−1 season−1, respectively. Soil organic matter, total N, total P, total K, available P and available K in PGVP soil were 27%, 49%, 42%, 3%, 200% and 54% greater than those levels in open fields, respectively. Average pH value in greenhouse soil was 0.53 lower than that in open field, and EC value in greenhouse soil (547.11 μS cm−1) was more than triple that in open fields (157.14 μS cm−1). Soil acidification and secondary salinization has occurred in PGVP. Soil P/K ratio in PGVP systems reflected that nutrient surplus in the South (0.080) and the Middle (0.077) were greater than those in the North (0.061). The differences in nutrient accumulation rate and soil pH changes among different regions were the comprehensive results affecting by both fertilization and soil types. We deduced that fertilization in PGVP in Shaanxi Province was excessive, which may further accelerate soil nutrient accumulation, acidification and secondary salinization.