Neem cake: Serves as bio-fertiliser

Prof. (Dr) R.D. Gupta
The residue left after extracting oil from seeds of neem, is called neem cake. Neem cake varies widely in its composition. However, on broad basis its composition is : (i) Crude protein – 13 to 35 per cent, (ii) Carbobydrates-26 to 50 per cent, (iii) Crude fiber-8 to 26 per cent, (iv) Ash-5 to 18 per cent, (v) Acid insoluble ash – 1 to 17 per cent.
The so-called ‘neem cake’ has considerable local potential. Although too bitter for animal feed yet it appears to possess unique promise for being used as bio-fertilizer. It contains more percentage of nitrogen, phosphorus and potassium as compared to farm yard manure or compost or sewage sludge. In addition to nitrogen, phosphorus and potassium, it also has large amount of calcium, magnesium – secondary plant nutrients. Neem cake is widely used in India to fertilize cash crops like sugarcane and vegetables. Ploughed into the soil, it protects roots of many plants from the assaults of nematodes and white ants. It is probably ascribed to its content of the residual limonoids, which have an ability to block insect growth or prove an active agent against root-knot nematodes.
It is surprisingly to note that neem cake when added to the water in rice fields, renders their soils more fertile. This is apparently due to presence of an ingredient in the Neem cake that inhibits or checks the growth of nitrifying bacteria. Actually these bacteria remain in the initial stage of their growth and never reach the exponential stage of the growth. This results into converting of native soil organic nitrogenous compounds or added nitrogenous fertilizers (urea, ammonium sulphate, ammonium chloride) into ammonical form only and not in nitrate form. Owing to this whole of the process, there is almost no leaching loss of nitrogen from the soil. Leaching loss of nitrogen, especially in rice growing soils occurs through nitrate (NO3) which never happens in such soils when Neem cake is added in their waters. Thus, the fertility of these soils is enhanced. Further it is added that there is no or very little conversion of nitrogenous compounds into useless nitrogen gas (N2), nitric oxide (NO) or nitrous oxide (N2O) etc.
Urea, when mixed with Neem cake also inhibits the growth of the nitrifying bacteria (as stated above) and cuts down on the amount of urea converted to nitrogen losses in the soils. Neem cake is applied in certain parts of Madhya Pradesh. Coating of urea with Neem cakes by physically mixing before application to rice fields, is also the practice in many parts of this state. Cakes of neem are also used in many areas of Chhattisgarh. In some of tribal areas of Sambalpur district, in Odisha, the farmers apply Neem cake at the rate of 500 Kg ha-1. The farmers believe that this practice helps not only in providing nutrition to plants but also controls pests.
Neem coated urea though available in the market, meant for using rice growing soils, has not been very much popularised particularly in our state. Similar is the case with sulphur coated urea which operate on the same principle. Need of the hour is, therefore, to start with the research in this line. For Neem coated urea, Agronomists and Soil Scientists of Sher-e-Kashmir University of Agricultural Sciences and Technology (SKUAST), Srinagar / Jammu should come forward to chalk out the strategies in collaboration with Krishi Vigyan Kendras (KVKs), command Area Development and Agricultural Department on large-scale.
Neem cake is not the only source of fertilizer. In some areas of India, especially Karnataka, the farmers grow Neem trees for their green leaves and twigs. After attaining good growth in both of the parameters, these are lopped. The lopped leaves and twigs are ‘Puddled’ into flooded rice fields before transplanting the rice seedlings. Neem leaves have been used as mulch in tobacco fields in some parts of Sri-Lanka. Use of neem leaves as mulch produce more numerous and longer branches in tomato plants.
(The author is former Chief Scientist KVK cum Associated Dean, SKUAST, Jammu)