Criteria of Nitrate Concentration in Soil Solution and Leaf Petiole Juice for Fertigation of Cucumber under Greenhouse Cultivation in Gyeonggi region

Abstract

To develop a technique for efficient management of fertility for cucumber in greenhouse, a quick test method to quantify nitrate (NO₃ - ) content in soil solution and leaf petiole juice using a simple instrument that are easy to use for farmers was investigated. N fertilizer (urea) was applied at 0, 50, 100 and 200% levels of the recommended application rate from 30 days after transplanting to harvest by soil fertigation treatments. Stable results were obtained from analysis of nitrate (NO₃ - ) using top 10 t h or 11 th leaf petioles collected between 10 to 11 am in the morning. Under the semiforcing culture, NO₃ - content of leaf petiole juice was highest at 60 days after transplanting (DAT) at all fertigation treatments. Appropriate NO₃ - content of leaf petiole juice was 2,418±78～2,668±118 at 45 DAT, 3,032±90～3,332±63 at 60 DAT, 2,709±50～3,158±155 at 75 DAT, 2,535±49～2,907±83 at 90 DAT, and 2,242±48 ㎎ L -1 at 105 DAT. In addition, appropriate NO₃ - content of soil solution was 167±9～212±15 at 45 DAT, 83±10～112±12 at 60 DAT, 49±3～92±6 at 75 DAT, 71±9～103±9 at 90 DAT, and 73±9 ㎎ L -1 at 105 DAT. The cucumber yield at 100% N level of fertigation was 7,770 ㎏ 10a -1 and no difference in yield was found at 200% N level of fertigation. However, there was 12% decrease in yield at 50% N fertigation and, 17% decrease at 0% N fertigation. Under retarding culture, NO₃ - concentration of leaf petiole juice was highest at 55 days after transplanting (DAT) at all fertigation treatments. Appropriate NO₃ - content of leaf petiole juice was 2,464±102～2,651±33 at 45 DAT, 3,025±71～3,314±84 at 55 DAT and 2,488±92 ㎎ L-1 at 65 DAT, respectively. Appropriate NO₃ - content of soil solution was 111±10～155±14 at 45 DAT, 93±7～147±14 at 55 DAT, 67±4 ㎎ L -1 at 65 DAT, respectively. The cucumber yield at 50% N fertigation was not different from 1,697 ㎏ 10a -1 of 100% N fertigation level and even with that of the 200% N fertigation. However, there was 21% decrease in yield at 0% N fertigation.