Impact of reduced potassium nitrate concentrations in nutrient solution on the growth, yield and fruit quality of melon in hydroponics

• Simple management of K nutrition in hydroponics can produce low K content melon.
• KNO3 restriction from anthesis to harvest produce 43% lower K content melon fruits.
• Fruit yield not decrease due to reduced K levels upto zero after anthesis to harvest.
• Translocation of plants parts K to fruits during reproductive stage is a key issue.
• We suggest quantitative management of K nutrition from vegetative growth period.

In general, foods with high K content are restricted to the patient with chronic kidney disease but our daily diets including melons are rich in K. Thus, they cannot eat usual diets with other family members, as it is eating normal melon fruits are like a dream to the dialysis patients. As a result of this normal diet restriction, their qualities of life (QOL) decrease greatly. Therefore, melon (Cucumis melo L. cv. Panna) were grown in nutrient solution with reduced KNO3 concentrations from anthesis till harvest to investigate its impact on the fruit K content while maintaining normal growth, yield and other fruit qualities. Three independent melon cultures were verified during the spring seasons from 2009 to 2011. In spring 2009, hydroponic culture of melon in nutrient solution with 1/1 and 1/4th levels of KNO3 has been investigated while the levels were decreased further as to 1/1, 1/2, 1/4, 1/8 and 1/16th or even as 1/1, 1/8 and 0, during spring 2010 and 2011, respectively. A general trend of decreasing K content in fruit was observed with the decrease of KNO3 concentration in nutrient solution without significant decline in fruit yield. Plant growth variables were not decreased greatly except root dry weights in nutrient solution with reduced KNO3. Citric acidity was decreased significantly due to KNO3 restriction in the first two cultures while soluble solids content was found to be decreased only in spring 2011. In spring 2009, melon plants were grown in nutrient solution with 1/4th KNO3 decreased fruits K by 39% compared to fruits K in standard nutrient solution whereas, it was decreased by about 35% and 43% when melon plants were grown in nutrient solution with 1/16th and 0 levels of KNO3 in the spring 2010 and 2011, respectively. Supplementation of melon fruits containing lower K than usual can be a very useful prevention method for the patient with chronic kidney diseases. It was evident that fruit K content was not decreased expectedly even after limiting the K level to zero. The possible reason behind might be the excessive absorption into the plant parts during vegetative growth and storage before the start of K restriction in turn translocated into the melon fruits. Therefore, consideration of K translocation from leaves and stems to fruits during fruit developmental stage is an important issue for this study. Quantitative supply of KNO3 to culture solutions of melon during vegetative growth would be lowers the fruit potassium considerably.