| As one of the most important fruits in the world,melon is very popular.In recent years,soilless cultivation technology has developed rapidly.The concentration of nutrient solution formula has a significant impact on the yield and quality of soilless cultivation crops.Due to the different nutrient uptake by crops under different fertilization rates,the quality of soilless cultivation crops will also be different to some extent.Further study of nutrient solution fertilization technology in greenhouse substrate cultivation is of great significance for improving crop quality and economic benefits.Therefore,whether it can effectively replace traditional chemical fertilizer to achieve the goal of weight loss and efficiency is worthy of our study.In this experiment,thin-skinned melon `Yumeiren'was selected as the test material,and different potassium nitrate concentrations were treated on the basis of special Yamazaki formula for melon.In 2017,five potassium nitrate concentrations were set: 0%,50%,75%,100% and 150%.They were expressed by NK0,NK50,NK75,NK100 and NK150,respectively.According to the results of 2017,the experimental treatment in 2018 increased by 65%,125% and 200%,that is,in 2018,five potassium nitrate concentrations were set: 0%,65%,100%,125% and 200%,respectively,expressed by NK0,NK65,NK100,NK125 and NK200.The effects of different potassium nitrate treatments on plant growth,nutrient uptake,fruit yield,quality and related enzyme activities and genes of thin-skinned melon were studied.The main results are as follows:1.During the growth and development of melon,the plant height,stem diameter and leaf number of melon increased with the increase of potassium nitrate concentration,while NK150 and NK200 treatment affected the growth index to a certain extent.The dry and fresh weight of roots and fruits treated with NK200 at fruit ripening stage was significantly lower than that of other treatments.At the same time,the chlorophyll content of leaves increased first and then decreased with the increase of potassium nitrate concentration.Pn was significantly lower in NK150 and NK200 treatments than in other treatments.2.Nitrogen and phosphorus uptake did not differ among treatments at vine elongation,fruit expansion and fruit ripening stages because of the different concentration of potassium nitrate;potassium uptake in NK0 treatment was the lowest,and there was no significant difference among other treatments.Potassium uptake increased with the increase of potassium nitrate concentration,while Ca and Mg contents in leaves decreased with the increase of potassium nitrate concentration.3.The yield per plant,soluble solids and soluble sugar content of NK0 and NK200 treatments were significantly lower than those of NK65-NK150 treatments.Compared with the yield increase effect of NK100,the yield per plant of NK65 and NK75 treatments had no difference;the utilization rate of K in vine elongation and fruit expansion was similar to that of NK50,NK65 and NK100 treatments;there was no significant difference among treatments at maturity.4.The contents of total esters and ethyl acetate in aroma components of fruits treated with NK0 were the lowest,and reached the maximum at NK100.There was no difference in Aroma Contents among NK65,NK100 and NK125 treatments.The variation trend of related components was the same as that of AAT,LOX enzyme activity and gene.In conclusion,under the condition of special substrate bag cultivation,there was no significant difference in yield,soluble sugar content and aroma between NK65 and NK75 treatment and NK100 treatment,and the effect was similar.Combining with the requirement of reducing fertilizer application,NK65 and NK75 treatments showed better results,that is,25% to 35% reduction of potassium nitrate was conducive to achieving high-quality production of melon. |
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