RLO 8 Lesson: Organic manures as a component of INM in rice After completing this lesson, you will be able to: Understand the role of different organic manures as a component of Integrated nutrient management in rice.

Organic manures: An overview Organic manures are valuable by-products of farming and allied industries, derived from plant and animal sources. Organic manures have the advantage of supplying secondary and micronutrient along with NPK, which is important for sustained production. Organic manures increase the biological activity in soil by providing support for earthworms, micro-organisms, fungi and bacteria and helps in nutrient cycling. They also stabilize soils against erosion and floods, detoxify ecosystems and may even help counteract climatic change by restoring soil’s capacity to carbon sequestration.

Organic manures used/ available as a component of INM in rice Bulky organic manures – supply plant nutrients in small quantities and organic matter in larger quantities. Examples, farmyard manure (FYM), biogas slurry, composts, green manure, poultry manure, etc. Concentrated organic manures – contain higher percentages of major plant nutrients (NPK) as compared to bulky organic manures. Examples, oilcakes, fish manure, etc.

Farmyard manure (FYM) FYM is a decomposed mixture of dung and urine of farm animals along with the litter (bedding material) and left-over material from roughages or fodder fed to the cattle. On an average, it contain 0.5% N, 0.2% P2O5 and 0.5% K2O. Under INM practices of rice, about 50% N should generally be applied through organic manures. Hence, approximately 12 tonnes/hectare FYM would be needed to supply 60 kg N in rice.

Biogas slurry Biogas (Gobar gas) plant produces methane and biogas slurry, which could be used as a valuable manure in rice. Biogas slurry is quite rich in nitrogen than the original ingredients due to addition of living and dead micro-organisms. Biogas slurry also contains phosphates, potash, sulphur and a number of micro-nutrients like zinc and iron. Biogas slurry is extremely cheap and is made by locally available material. It can be directly used in rice after mixing with irrigation water.

Composts There are two kinds of composts available – Rural and Urban composts. Rural compost mostly uses crop residues and cattle dung and urine as the raw material, while urban compost uses city refuse which includes kitchen wastes, industrial wastes, waste materials from vegetable markets etc. as the raw materials. Both rural and urban composts could be successfully used in rice as a component of INM. The exact quantity would depend on the percentage of nutrients available in them and the proportion of nutrients to be supplied.

Green manures Green-leaf manuring : green leaves and tender green twigs collected from shrubs and trees grown on bunds, wastelands and nearby forest areas. The common shrubs and trees used are Glyricidia (Glyricidia maculata), Sesbania (Sesbania speciosa), Karanj (Pongamia pinnata), etc. This system is common in eastern, southern and central India. Green manuring in situ :green manures are grown and incorporated in the same field which is to be green-manured, either as a pure crop or as an intercrop with the main crop. Advantages: Building of organic matter and improved soil structure Nitrogen fixation and enhanced soil microbial activity Enhanced availability of native soil nutrients Improvement in soil physical properties and benefits of rooting action Weed suppression, soil and water conservation, enhanced crop yields

Many options are available for rice crop

Source: Yawalkar et al.(1996) Table. Potential N contributions of N- fixing legumes to succeeding crops in Indian soils Name Botanical name Sowing season Average yield of green matter (t/ha) N (% on green weight basis) N added (kg/ha) Sannhemp Crotalaria juncea Kharif 15.2 0.43 84.0 Dhaincha Sesbania aculeata 14.4 0.42 77.1 Mungbean Vigna radiata 5.7 0.53 38.6 Cowpea Vigna ungiculata 10.8 0.49 56.3 Guar Cyamopsis tetragonoloba 0.34 62.3 Senji Melilotus alba Rabi 20.6 0.51 134.4 Khesari Lathyrus sativus 8.8 0.54 61.4 Berseem Trifolium alexandrinum 11.1 60.7 Source: Yawalkar et al.(1996)

Before transplanting/ sowing of rice crop, sesbania (dhaincha) and sannhemp (sanai) are the better crops for green manuring. On an average, green manuring saves 60 kg nitrogen/ha in rice cultivation. Green manuring is known to increase grain yield of succeeding rice by 20-50% across the different states of India.

Poultry manure It is a rich organic manure, since liquid and solid excreta are excreted together resulting in no urine loss. It can be applied to the soil directly as early as possible, and then immediately mixed into the soil. Fresh poultry manure contains about 1.5% N, 1.1% P2O5 and 0.5 % K2O. It is suitable for rice crop also and can complement the chmical and bio-fertilizers in rice cultivation.

Oilcakes Many kinds of oilcakes can be used as a source of nutrients in crops. Oilcakes contain not only nitrogen, but also some phosphorus and potassium, along with a large proportion of organic matter. Before application to rice or any other crop, oilcakes should be well-powdered to facilitate their application and decomposition by soil microorganisms. Depending on crop, oilcakes are applied broadcast, drilled or placed near the root zone. The average nutrient content of important oilcakes is given on the next slide.

Average nutrient content of important oilcakes K2O (%) Castor cake 4.3 1.8 1.3 Cottonseed cake undecorticated 3.9 1.6 Neem cake 5.2 1.0 1.4 Karanj cake 0.9 1.2 Safflower cake undecorticated 4.9 Groundnut cake 7.3 1.5 Linseed cake

Summary Organic manures are the very important component of integrated nutrient management practices in the cultivation of rice. Besides supplying nutrients, they also improve the physical, chemical and biological properties of soil. Manures like, FYM, composts, green manures and oilcakes are integral part of INM in rice.