Nitrogen sources for rice in typic ustropept wetland soil in India
2001
Suresh, S. (Tamil Nadu Agricultural Univ., Kovilpatti - 628501, Tamil Nadu (India))
There is enormous potential to increase rice production in India and elsewhere by enhancing the efficiency of applied N. This can be done by matching the source of N fertilizer with soil-crop management systems. Therefore field experiments, one in Kharif (Jul-Oct) and the other in rabi (Oct-Feb) crop seasons with rice varieties ADT36 and IR20, respectively, were conducted in sandy clay wetland rice soil in India. Grain yield was found higher with the use of neem cake coated urea and urea gypsum as fertilizer, than the conventionally applied prilled urea. Neem cake is waste material from the manufacture of oil from the neem tree. The oil is a known botanical pesticide. Combined application of Gliricidia green leaves as fertilizer (called green leaf manure) with prilled urea was less efficient in increasing yield. Application of N at 175 kg/ha (kilogram per hectare) was found to be necessary for getting higher grain yield of rice during both crop seasons, when ordinary prilled urea was used. Application of neem cake coated urea recorded the lowest Nitrosomonas population in the soil compared to prilled urea. Nitrosomonas are bacteria that convert the nitrogen from the fertilizer into a simpler form that the plant could directly use. The loss of N by downward movement into the lower part of the soil (a process called leaching) was lowest when neem cake coated urea and urea gypsum was used, and highest at prilled urea at 225 kg N/ha. Application of neem cake coated urea also increased the available KMnO4-N content of the soil compared to prilled urea. The use of neem cake coated urea and urea gypsum could save 50 kg N/ha
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