Study On K,N And P Absorption And Potassium Diagnosis Of Lettuce At Different K Fertilizer Level

Potassium is one of essential nutrient of leaf vegetables, which has a degree of impact on yield, quality, nutrient and economic benefit of leafy-vegetables in the growth and development process of leafy-vegetables. There are many types of vegetable cultivations in Chongqing of China, at the same time, a lot of questions about vegetable quality are left in the countrywide at present. So far, Chongqing has not carry out systematic research about demand characteristics and diagnosis of potassium on leafy vegetables. Therefore, to study the potassium absorption and distribution of lettuce in all the growth cycle, and how to improve the lettuce’s yield、quality and soil available potassium are major issues. In order to explore the best adaptability of potassium fertilizer, field experiments were set up to study the potassium absorption and diagnosis of lettuce. The main results are followed.(1) The biomass of the two lettuces had a tendency of increase firstly and then drop down. The growth rate of Jinxiangyu had a close relationship with growth period. After the regression analysis of biomass and days, the optimal regression equations were gained which was cubic curve (y=bo+b1x+b2X2+b3x3).The biomass of K2was the highest between the two lettuces. After the regression analysis of potassium uptake and days, the optimal regression equations were gained which was power curve (y=b0xb1). From the view of growth stages, the potassium content of opening period was the highest. The max potassium uptake of the two lettuces were173.57kg/hm2�'�168.73kg/hm2in100days. From the view of different growth stages, the potassium content of opening period was the highest; the biomass and potassium uptake of Xiangyoujiuhao were higher than Jinxiangyu.(2) The application of potassium fertilizer could significantly increase the yield of lettuce; and Xiangyoujiuhao was higher than Jinxiangyu. Different varieties lettuce had different potassium absorption in the harvest, Jinxiangyu was147.4-167.3kg/hm2while Xiangyoujiuhao was129.3-164.2kg/hm2, K uptake of the two lettuce averaged by2.93kg and2.87kg per1000kg, maybe the data can be the basis for the amount of potassium fertilizer of in the lettuce production.(3) Different K rates on the quality of lettuce were different. Suitable amounts of K could improve the content of sugar and reduce the nitrate and VC, while the amino acid content had a positively associated relationship with K rates. The quality ingredients of different varieties of lettuce were different, the amino acid of Xiangyoujiuhao was higher while nitrate of Jinxiangyu was higher.(4) The nitrogen content of opening period was the highest between52.1and55.1g/kg. The nitrogen uptake rate of the two lettuces had a tendency of increase firstly and then drop down. The nitrogen absorption of K2treatment was the highest between all the treatments. The application of potassium fertilizer could also increase the nitrogen absorption of lettuce. Nitrogen uptake by lettuce increased more and more with the growth. At harvest time, two varieties of lettuce nitrogen absorption reached to154kg/hm2and153.7kg/hm2, the average of nitrogen absorption of the two lettuce were2.61kg and2.71kg per1000kg.(5) The application of potassium fertilizer could also increase the phosphorus absorption of lettuce; the maximum value was21.36kg/hm2and21.57kg/hm2respectively. The average of phosphorus absorption of the two lettuce were0.390kg and0.384kg per1000kg. But different dosage of potassium fertilizer treatment had no significant effects on lettuce phosphorus absorption. Maybe we should take other measures to improve the absorption of phosphorus in lettuce.(6) The stability order of total N, P, K content and uptake were K>N>P. To product1000kg lettuce, the proportion of N,P,K were1:0.15:1.12(Jinxiangyu) and1:0.14:1.06(Xiangyoujiuhao).(7)The stability order of potassium content of the part of lettuce were old leaves> main vein> functional leaves> side leaves>young leaves. Only the potassium content of the old leaves in fast growing period had a significant relationship with biomass and K rates. So, we could suggest the time of potassium diagnosis was in fast growing period, and the site of lettuce was the old leaves.