| 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 the significance of the study on vegetable production in our city is becoming more and more obvious. In order to explore the best adaptability between different potassium fertilizers and leafy-vegetables, reduce potash costs and improve economic benefits of leaf vegetables, field experiments were set up to study the effects of different combination mode between potassium fertilizers and other fertilization on yields, quality and economic benefit of leafy-vegetables. The main results are followed.(1) Nutrient content and uptake of lettuce and Chinese cabbages were obvious difference at N15P5K10(OPT) in different reasons. Total N, P, K content and uptakes of lettuce were respectively3.50%,0.713%,3.93%and47.9kg/hm2,9.66kg/hm2,51.4kg/hm2.Total N, P, K content and uptakes of Chinese cabbages were respectively5.10%,0.575%,5.08%and77.5kg/hm2,8.76kg/hm2,77.2kg/hm2. Total N, P, K content and uptakes of lettuce in different yield levels were respectively2.92%,0.658%,4.43%and79.6kg/hm2,18.7kg/hm2,120kg/hm2(high yield level),3.50%,0.721%,5.42%and60.0kg/hm2,12.4kg/hm2,93.5kg/hm2(medium yield level),2.89%,0.616%,4.46%and30.3kg/hm2,6.33kg/hm2,45.9kg/hm2(low yield level), orders of it was K,P,N. The highest content (5.42%) and uptakes (120kg/hm2) were respectively at medium and high yield area, and the largest variability and worst stability of N, P, K content and uptake of lettuce were total potassium at each yield area. Total N, P, K content and uptakes of Chinese cabbage were respectively4.78%,0.726%,6.21%and133kg/hm2,20.4kg/hm2,174kg/hm2(high yield level),5.11%,0.593%,4.70%and88.3kg/hm2,10.1kg/hm2,81.1kg/hm2(medium yield level),3.59%,0.481%,3.81%and33.4kg/hm2,4.20kg/hm2,36.3kg/hm2(low yield level). The highest N content of lettuce was5.11%at medium yield level, total P and K was respectively0.726%and6.21%at high yield level, and total nitrogen, phosphorus, potassium content were most stable in high yield area, the stability order of total potassium content was K>N >P. Nutrient demand of Chinese cabbage was higher than lettuce, and there was no particular difference of N, P, K content and uptakes in the two different potassium fertilizers. KC1was recommended to be planted in lettuce and Chinese cabbage.(2) Study on effects of topdressing potassium chloride fertilizer on lettuce showed lettuce yield was obviously increased by15.8%(place1) and16.8%(place2) at basal application of potassium chloride fertilizer, compared to other treatments. The influence on vitamin C and amino acid content of lettuce leaf were different in different periods of topdressing KC1. The highest soluble sugar contents of lettuce leaf and stem were respectively1.665%and1.273%at basal application of KC1, and nitrate content of lettuce leaf and stem was respectively decreased by6.1%～29.8%and8.0%～16.6%at topdressing KCl compared to basal application of KCl. The highest yields, partial factor productivity from applied K, potassium agronomic efficiency and potassium utilization of lettuce were respectively46816kg/hm2,312.1kg/kg,42.5kg/kg,48.2%(place1) and43574kg/hm2,290.5kg/kg,41.7kg/kg,32.2%(place2) at basal application of KC1. It was no obvious regularity of total N and total P content of lettuce by topdressing KC1at different periods, the highest total K content were5.29%(leaf) and5.74%(stem), and total Cl content of lettuce leaf and stem were respectively0.396%(place1),0.905%(place2) and0.404%(place1),1.36%(place2) at basal application of KC1. The highest profit of lettuce was at basal application of KC1, respectively43679yuan/hm2and40437yuan/hm2. So KCl as basal fertilizer was appropriate to planting lettuce and other leaf-vegetables at autumn in Chongqing.(3) Study on the differences of lettuce and Chinese cabbages which were planted with potash and fertilization in different times showed that the highest yield, partial factor productivity from applied K, potassium agronomic efficiency and potassium utilization of lettuce and Chinese cabbages were respectively41882kg/hm2,279.2kg/kg,37.3kg/kg,26.2%(lettuce) and69213kg/hm2,461.4kg/kg,63.8kg/kg,41.1%(Chinese cabbage) at K1-3(basal application50%+leafage extending stage50%), and the most physiological efficiency of lettuce and Chinese cabbage were respectively277.4kg/kg and449.2kg/kg at K2-4(rosette stage50%+leafage extending stage50%). Amino acid content of lettuce leaf was improved by56.6%at basal application of KCl, the largest decline of nitrate content of lettuce leaf was23.7%at K2-3(basal application50%+leafage extending stage50%). Vitamin C content order was basal application100%<basal application50%+rosette stage50%<basal application50%+leafage extending stage50%<rosette stage50%+leafage extending stage50%, and soluble sugar content of Chinese cabbage was significantly increased by23.4%-92.9%.It was more advantageous to decrease nitrate content of Chinese cabbage by K2SO4than KCl. Total N, P, K, Cl contents of lettuce and Chinese cabbages were different in vegetable types and fertilization methods by topdressing potassium fertilizers at different periods.The biggest increase of total N content of lettuce leaf and stem were respectively8.0%and4.7%at K1-4(rosette stage50%+leafage extending stage50%) and effect of KCl was better than K2SO4. Economic benefits and input-output ratio of KCl was higher than K2SO4, the input-output ratio of lettuce at application of KCl was better than KaSO4.Compared to KCl, yield-increasing effect of lettuce and Chinese cabbages was not significant at topdressing K2SO4. In summary, KCl was recommended to be basal-fertilizer in Chongqing because of high cost of K2SO4. |
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