Effect of fertilization on yield, net income and soil environment in Qingdao protected vegetable production systems

To increase fertilizer use efficiency, reduce fertilizer cost and limit environmental pollution by fertilization, the study on effects of fertilizer application on yield, net income and soil environment in protected vegetable production systems in Qingdao were conducted. The study showed that excessive use of nitrogen (N), phosphorus (P) and potassium (K) fertilizers in tomato and cucumber fields, with N, P₂O₅ and K₂O average annual application rates of 1 841.5 kg·hm^-2, 864.0 kg·hm^-2 and 1 978.7 kg·hm^-2 for cucumber; and 1 436.7 kg·hm^-2, 833.6 kg·hm^-2 and 1 643.7 kg·hm^-2 for tomato, respectively. Organic manure and chemical fertilizers were applied at relatively reasonable rates, suggesting that much attention had been paid to the use of organic manure. Annual N, P₂O₅ and K₂O application rates had significant effects on annual yield and net income. Linear equations adequately explained the relationships of yield, net income with fertilizer application rate in the region. Soil nitrate-N content increased with increasing annual application rate of N. The protected vegetable fields of 31.4% farmer household had high or relatively high nitrate-N contents. Soil available P also increased with increasing annual P₂O₅ application rate. Similarly, 74.3% farmer household' protected vegetable fields had high soil available P content. Protected vegetable soils apparently acidified, 68.6% farmer household' protected vegetable field soil was acid or subacid, showing acidifying tendency. The results suggested that N, P₂O₅ and K₂O application rates should drop. Also new techniques such as computerized fertilization, integrated water-fertilizer managements, bacteria treated straws, soil straw return, etc., should be popularized to ensure the development of sustainable protected vegetable production in Qingdao.