| In order to investigate the effect of ammonium polyphosphate?APP?proportion in total P of nutrient solution on the growth of greenhouse vegetables,two kinds of vegetables,lettuce and leaf lettuce,were chosen for the study in this paper.To study the effects of APP proportions in total P on growth,yield and quality of the selected vegetables,seven different APP/PDP P ratios were set up,they are:0:100%,25%:75%,33%:67%,50%:50%,67%:33%,75%:25%,100%:0,under the same supply level of other nutrients,so as to determine the appropriate APP/PDP ratio for different vegetables.The main conclusions are as follow:?1?Under the condition of same level of P supply,the net photosynthetic rates?Pn?of lettuce and leaf lettuce were effectively promoted by properly increasing the proportion of APP in total P.The highest Pn of lettuce was obtained(15.01?mol·m-2·S-1)when APP/PDP was 1:1,which was significantly higher than that of CK?16.53%?.The highest Pn of leaf lettuce was16.60?mol·m-2·S-1 when APP/PDP was 1:1,which was significantly higher than that of ACK?12.08%??2?Under the same supply level of the P,the SPAD values of the lettuce and leaf lettuce were effectively promoted by properly increased APP proportion in total P innutrient solution.When APP/PDP was 2:1,the SPAD value of lettuce was 22.27,which was significantly higher than that of other treatments,and significantly increased by 26.69%compared with CK.When APP/PDP was 1:2,the SPAD value of leaf lettuce was 40.70,which was increased by 20.77%compared with ACK.?3?The content of Vc in lettuce was effectively increased by increasing the proportion of APP in total P.When APP/PDP was 2:1,Vc content of lettuce was 23.50 mg/100g,which was20.33%higher than CK.When APP/PDP was 3:1,the highest soluble sugar content of lettuce was 50.63 mg/g,which was significantly higher than that of CK.When APP/PDP was 2:1,the highest content of soluble proteinof lettuce was 4.50mg/g,which was significantly higher than that of CK?9.49%?.?4?Under the condition of keeping the same level of P supply,the Vc content of leaf lettuce was effectively increased by properly increasing the proportion of APP in total P in nutrient solution.When APP/PDP was 3:1,the highest content of Vc and soluble sugar were 24.43mg/100g and 37.11 mg/g,respectively.When APP/PDP was 2:1,the highest content of soluble protein was 5.65 mg/g.?5?Under the same supply level of P,average weight lettuce per plant was effectively increased by properly increasing of APP ratio in total P.The average weight per plant was 99.43g when APP/PDP was 2:1,which was increased by 13.69%compared with CK.At the same time,P uptake of above-ground-part of lettuce reached 16.47 mg per plant.The highest yield of leaf lettucewas 117.10g?APP/PDP=2:1?,which was 16.99%higher than that of ACK.When the APP/PDP was 1:1,the highest uptake of P in the above-ground-part of leaf lettuce was 24.41mg/plant.?6?Based on the TOPSIS analysis of analytic hierarchy process and entropy weight method,the comprehensive evaluation of lettuce and leaf lettuce was carried out.The optimal schemes were as follows:when grown at 2/3APP and 1/2APP,lettuce and leaf lettuce were the best in growth,yield and quality,respectively. |
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