Effects Of N,K,Mo On The Nitrate Accumulation,Yield And Quality Of Water Spinach

By means of hydroponic culture, applying three-factor (N, K, Mo) five-level orthogonal rotational design and computer technology, this paper studied effects of N, K, Mo application on the nitrate accumulation, yield and quality of water spinach (Ipomoea aquatica, Forsk. ) , built corresponding regression mathematical models, and analyzed respective effect and interactions of the three fertilizer factors on them and correlations between nitrate accumulation and NR, GS activity of water spinach . The result indicated:(1) N was the main factor in nitrate accumulation, and the nitrate content of water spinach significantly increased with the rising of N fertilization amounts. In relatively low concentration (the level codes of K, Mo range from - 1. 682 to 0) the nitrate content increased with the rising of K fertilization amounts and significantly decreased with the rising of Mo; in comparatively high concentration (the level codes of K, Mo range from 0 to 1.682) the nitrate content decreased with the rising of K fertilization amounts and increased with the rising of Mo. There were significantly negative interactions between the three factors to the nitrate accumulation of water spinach, that was it would decrease the nitrate content by the high supply of K, Mo on the basis of supplying N, especially when supplying maximum N (the level code of N was 1.682) the effect was more significant.(2) There was a negative correlation between NR activity of water spinach and N fertilization amounts, but the NR activity increased with high supply of K. In relatively low concentration (the level code of Mo ranges from - 1.682 to 0) the NR activity increased with the rising of Mo fertilization amounts, but decreased with the rising of Mo in comparatively high concentration (the level code of Mo range from 0 to 1.682). In the three factors the effect of K on it was greatest, next was Mo. The NR activity of water spinach had a extremely significantly negative correlation with the nitrate accumulation, and the correlated coefficient was -0.7724.(3) In relatively low concentration (the level code of N ranges from - 1.682 to 0) the GS activity of water spinach decreased with the risingof N ferti1ization amounts and increased with the rising of N incomparatively high concentration (the level code of N ranges from 0 to 1.682). It increased with the rising of Mo fertilization amounts and decreased with the rising of K. There was a negative correlation between GS activity of water spinach and nitrate accumulation, but the correlation was not significant.(4) The yield of water spinach significantly increased With proper fertilization of N, K, Mo, and N was the major factor influencing the yield, next was K, the smallest was Mo. The quality of water spinach also significantly improved with appropriate fertilization of N, K, Mo. In the three factors the contribution of N to the yield and quality of water spinach was greatest, effect of K on vitamin C and dry matter content as well as that of Mo on protein content came second, and effect of Mo on vitamin C and dry matter content as well as that of K on protein content were minimum. There were significantly positive interactions of N-K and K-Mo and negative interaction of N-.Vto to the yield and quality of water spinach, that was it would benefit to increasing the yield and improving the quality by supplying K, Mo with the rising of N fertilization amounts, and it would decrease the yield and nutrient content by supplying K or Mo with the rising of Mo or K fertilization amounts.(5) On the basis of mathematical models between N, K, Mo fertilizer and yield, nitrate content, vitamin C content, protein content as well as dry matter content of water spinach, applying the method of probability analysis, and through synthetical optimixing the optimum combination of N, K, Mo for hydroponic culture of water spinach was obtained .which was N: 354.9-382. 2mg/L; K. 514. 8-557. 7mg/L: Mo: 62. 4-76. 8Hg/L.