Abstract
Soil-related obstacles resulting from continuous monoculture have limited the sustainable development of the tomato industry in China. An experiment on tomatoes with seven continuous monoculture treatments (the 1st, 3rd, 5th, 7th, 9th, 11th, and 13th crops, respectively) was conducted in a solar greenhouse, to investigate the influence of monoculture on soil quality. Most soil quality indicators first increased and then decreased with increasing continuous monoculture crops, and significant differences among crops were observed. Indicators at the 13th crop were significantly lower than those at the other crops in terms of average well color development (AWCD), substrate richness (S), the Shannon diversity index (H), and the McIntosh index (U) of the soil microbial community (SMC), soil urease (UR), and neutral phosphatase (N-PHO) activities, and available nitrogen (AN) and potassium (AK). However, fungal abundance (FUN) at the 13th crop was significantly higher than that at the other crops. As principal component analysis (PCA) revealed, SMC functional diversity at the 1st, 11th, and 13th crops were similar, and were obviously distinguished from those at the other crops. Moreover, the tomato yield was significantly and positively correlated with soil-available potassium and SMC functional diversity indexes. Our findings indicated that short-term continuous monoculture, e.g., for fewer than seven or nine crops, was beneficial for soil quality improvement. However, continuous monoculture for greater than 11 crops had adverse effects on soil enzyme activities, soil microbial abundances, soil chemical properties, soil SMC functional diversity, and the tomato yield, particularly at the 13th crop.
Highlights
Solar greenhouses offer advantages such as a high land utilization rate, short production cycle, and high technical content
Our study demonstrated that the total soil microbial abundance, bacterial abundance, B/F value, and soil microbial community (SMC) functional diversity indicators, initially increased and gradually decreased with the increase of continuous monoculture crops in a solar greenhouse
The changes in soil microbial abundance and SMC functional diversity indicators suggested that short-term continuous monoculture was beneficial to soil microbial accumulation and SMC functional diversity promotion
Summary
Solar greenhouses offer advantages such as a high land utilization rate, short production cycle, and high technical content. They are suitable for crop production in the cold regions of northern China [1,2], and provide much higher yields and incomes than open field cultivation [3,4]. Most research has focused on screening superior varieties to alleviate pests and disease, introducing grafting techniques to enhance plant resistance, applying organic fertilizer to improve soil quality, or selecting alternative rotations to balance soil nutrition [18,19,20]. The relationships between soil microbial properties, soil enzyme activities, and continuous tomato monoculture in solar greenhouses, remain poorly understood
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