Kumar Rajesh, Devakumar C, Kumar Dinesh, Panneerselvam P, Kakkar Garima, Arivalagan T
Division of Agricultural Chemicals and Division of Agronomy, Indian Agricultural Reseach Institute, New Delhi 110 012, India.
J Agric Food Chem. 2008 Nov 12;56(21):10183-91. doi: 10.1021/jf802139q. Epub 2008 Oct 9.
The utility of neem (Azadirachta indica A Juss) oil coated urea as a value-added nitrogenous fertilizer has been now widely accepted by Indian farmers and the fertilizer industry. In the present study, the expeller grade (EG) and hexane-extracted (HE) neem oils, the two most common commercial grades, were used to prepare neem oil coated urea (NOCU) of various oil doses, for which mineralization rates were assessed in four soils at three incubation temperatures (20, 27, and 35 degrees C). Neem oil dose-dependent conservation of ammonium N was observed in NOCU treatments in all of the soils. However, a longer incubation period and a higher soil temperature caused depletion of ammonium N. Overall, the nitrification in NOCU treatment averaged 56.6% against 77.3% for prilled urea in four soils. NOCU prepared from EG neem oil was consistently superior to that derived from hexane-extracted oil. The performance of NOCUs was best in coarse-textured soil and poorest in sodic soil. The nitrification rate (NR) of the NOCUs in the soils followed the order sodic > fine-textured > medium-textured > coarse-textured. The influence of edaphic factors on NR of NOCUs has been highlighted. The utility of the present study in predicting the performance of NOCU in diverse Indian soils was highlighted through the use of algorithms for computation of the optimum neem oil dose that would cause maximum inhibition of nitrification in any soil.
印楝（Azadirachta indica A Juss）油包膜尿素作为一种增值氮肥的效用现已被印度农民和化肥行业广泛接受。在本研究中，使用两种最常见的商业等级的榨油级（EG）和己烷萃取（HE）印楝油来制备不同油剂量的印楝油包膜尿素（NOCU），并在三种培养温度（20、27和35摄氏度）下在四种土壤中评估其矿化率。在所有土壤的NOCU处理中均观察到铵态氮的印楝油剂量依赖性保存。然而，较长的培养期和较高的土壤温度导致铵态氮的消耗。总体而言，在四种土壤中，NOCU处理的硝化作用平均为56.6%，而粒状尿素为77.3%。由EG印楝油制备的NOCU始终优于由己烷萃取油制备的NOCU。NOCU在质地粗糙的土壤中性能最佳，在盐碱土中最差。土壤中NOCU的硝化率（NR）顺序为盐碱土>质地细的土壤>质地中等的土壤>质地粗糙的土壤。强调了土壤因子对NOCU硝化率的影响。通过使用计算在任何土壤中能最大程度抑制硝化作用的最佳印楝油剂量的算法，突出了本研究在预测NOCU在印度不同土壤中性能方面的效用。
