Distribution of inorganic N fractions and N availability indices in the rice soils of Meghalaya

摘要

The potentially mineralizable N was evaluated by different chemical oxidation methods in 53 rice soils representingfrom six districts of Meghalaya. A wide variation in dry matter yield and N uptake was observed in the sampled, ranging from 13.7 - 55.8g pot' and 155 - 1527 mg pot' with a yield and uptake response of 13 -91 and 28-171 per cent, respectively. The ammoniacal N in the soils rangedfrom 28-207 kg ha~(-1) with a mean of 88 kg ha~(-1) ', while the nitrate N rangedfrom 3 -44 kg ha~(-1) (mean 22 kg ha~(-1) ). Highest available N was recorded with dichromate oxidation that rangedfrom 1004 - 4390 kg ha~(-1) , whereas the alkaline permanganate akd acid permanganate extractable N recorded 182 - 603 and 157 - 470 kg ha~(-1) , respectively. Alkaline KMnO_4 and acid KMnO_4extractableN showed significantly higher relationship with all the plant growth pararfieters over the other extraction methods and the critical limits were found to be 320 and 286 kg ha~(-1) , respectively. The fertilizer recommendations for rice have to be modified so as to enhance the N use efficiency in the soils of Meghalaya.