Abstract:

The purpose of this paper is to elucidate the optimum amount of nitrogen（N），phosphorus （P2O5）and potassium（K2O）in cucumber cultivated in solar-greenhouse under integral control of water and fertilization. The effects of nitrogen，phosphorus and potassium on the yield and quality of cucumber were investigated with the three factors and double saturated D-optimum design. A mathematical model for the optimization was established using nitrogen，phosphorus and potassium amounts as the independent variables，and the yield and quality of cucumber as objective function. The results showed that nitrogen，phosphorus and potassium significantly influenced the yield and quality of cucumber，but phosphorus and potassium had a higher effect than nitrogen. When the amount of N，P2O5，K2O reached to 861.5 kg · hm-2，306.1 kg · hm-2 and 1 082.0 kg · hm-2 respectively，the marginal yield effect reduced to zero. Similarly，the marginal quality effect reduced to zero when the amount of N，P2O5，K2O reached to 688.4 kg · hm-2，320.2 kg · hm-2 and 1 230.2 kg · hm-2 respectively. Through simulated computation，the schemes of optimized fertilization of cucumber were finally obtained. The yield of cucumber could reach to 138 000 kg · hm-2 or more，and the comprehensive score of quality achieved to 88 when the fertilizer rates are N 665.5–827.6 kg · hm-2，P2O5 267.9–334.3 kg · hm-2，K2O 1 043.1–1 235.0 kg · hm-2. The suitable ratio of N︰P2O5︰K2O is 1︰0.40︰1.53.

Key words: cucumber, nitrogen, phosphorus, potassium, solar greenhouse, integral control of water and fertilization