chemical fertilizers as a component of inm in rice

Chemical Fertilizers as a component of INM in Rice

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Introduction

Different kinds of chemicalfertilizers are available to supply nutrients to the rice crop.



Chemical fertilizers supply largest amounts of nutrients to rice crop even when INM practices are followed.

On an average rice crop removes 20-27 kg N, 8-18 kg P2O5 and 20-40 kg K2O per tonne of grain harvested.

Nitrogenous fertilizers

Fertilizers used are: Urea, ammonium sulphate, DAP, CAN, Nitrification inhibitors’ coated urea and slow release fertilizers



A dose 100-150 kg N/ha is recommended for high yielding varieties of rice. Hybrids where yield potential ranged between 8-10 t/ha will need higher doses of N (180-200 kg N/ha).

Improving nitrogen use efficiency of rice



Nitrification inhibitors can also be used to reduce N losses. Contd…

Nitrogen use efficiency (NUE) of rice, especially under lowland conditions, is low, i.e. 30-50%.

Significant proportion of N is lost by denitrification, ammonia volatilization and leaching etc. in rice.

NUE can be increased by split application, deep placement and use of nitrification inhibitors and slow-release N fertilizers.

Two split doses are recommended for short and medium duration varieties, while 3 split doses are recommended for long duration varieties.

Sulphur coated urea is also a useful fertilizer for rice.


Chemical Fertilizers as a component of INM in RiceImproving nitrogen use efficiency of rice

Nitrification inhibitors retard the nitrification process in soil and thereby reduce leaching and denitrification of N.

Number of chemicals have been reported to have nitrification inhibiting properties. Most widely tested chemicals are: N-Serve (2-chloro 6 trichloromethyl pyridine), AM(2-amino-4-chloro-6methyl pyrimidine), DCD(dicyandiamide) and ST (Sulphathiazole).

Increased rice yields and increased NUE in India has been reported through N-Serve, AM, ST and DCD.

Neem oil coated urea (500-1000 ppm) enhances grain yield and nitrogen use efficiency in rice. This product is now available in the Indian market.

Phosphatic fertilizers



The general practice is to broadcast P fertilizers just before final puddling in the case of transplanted rice and final ploughing in the case of direct seeded rice

contd….

Single super phosphate, diammonium phosphate (DAP), rock phosphate(RP) and N:P:K fertilizers are the important sources to supply P to rice

On an average rice needs 40-60 kg P2O5/ha

P application is generally recommended at final puddling before transplanting/final ploughing or at broadcasting in the case of direct seeded rice

In the case of non-availability of fertilizer in time, it can be top-dressed within 30 days of transplanting and at the most may be extended to 40 days on medium soils



Phosphatic fertilizers

Particle size of RP is an important property that affects its efficiency.

Dipping of roots of rice seedlings in P-slurry has also been found reasonably good.

There has been considerable interest in the direct use of rock phosphate (RP) in rice.

Rock phosphate needs to be generally applied 3-4 weeks before transplanting and should be incorporated in soil for better results.

Some workers also recommend higher rates of RP application as compared to water soluble P fertilizer.

Higher efficiency of RP in acid soils is due to lesser P fixation.

Potassic fertilizers



Due to high costs mostly MOP is used for rice. Potassium application is mostly recommended at the time of sowing/ transplanting.

Response of kharif rice is generally higher than rabi rice. This could partly be due to the fact that disease incidence in rice is more during kharif season.

Potassium application reduces the severity of bacterial diseases of rice. Severity of fungal diseases such as brown leaf spot, Cercospara leaf spot, sheath blight, stem rot and Helminthosporium sp is also reported to be reduced by K application.

There are mainly two potassium fertilizers namely, muriate of potash(MOP) (KCl) containing 60% K2O and sulphate of potash(SOP) (K2SO4) containing 48% K2O.

Sulphur



The other kind of sources of S are those materials which are marketed and used only as a source of S. These are referred to as S-fertilizers and include elemental S, gypsum, iron pyrites and phosphogypsum(a byproduct of phosphoric acid industry). Most S is applied to soil at sowing.

Substitution of high analysis fertilizers such as urea and DAP for ammonium sulphate and single superphosphate has been the main cause for wide spread S deficiency in Indian soils.

In general, rice responds to 20-40 kg S/ha.

There are 2 kinds of sources of S. The first kind are the popular fertilizers containing S as the nutrient other than that for which fertilizer is applied. For example, single superphosphate (SSP) is marketed as phosphate fertilizer but contains 12% S.

Micronutrients fertilizers

If zinc is not applied in soil at transplanting/ sowing and zinc deficiency symptoms appear, foliar spray of 0.5-1.0% zinc sulphate is recommended.



Deficiency of 3 micronutrient have been reported in rice-growing areas of India. First of all zinc deficiency in rice fields was noticed in tarai soils. Later deficiency of Fe was noticed on sandy soils of Punjab. Of late boron (B) deficiency in rice has been reported on highly calcareous soils of Bihar.

Zinc sulphate and zinc oxide are the important zinc fertilizers available in India.

Application of 25 kg zinc sulphate(heptahydrate)/hectare is generally recommended in India (for rice). Dipping rice roots in 2-4% ZnO suspension has also been found to be very effective.

Contd…..




When foliar application is must, solution of 0.2% borax (with lime twice the weight of borax) is recommended to avoid injury to foliage).

Fe chlorosis in rice is better controlled by foliar spray of 0.5% Fe-sulphate.

Soil application of B should be made when deficiency of B has been established. Indiscriminate use may result in toxicity of plants.


Chelated Zinc - Powder - 12% Zn - EDTA



Zinc Sulphate - Crystalline (ZnSO4.7H2O) - 21% Zn

Zinc Sulphate Mono Hydrate - Powder (ZnSO4.H2O) - 33% Zn

Ferrous Sulphate - Crystal/Powder (FeSO4.H2O) 19% Fe

Copper Sulphate - Crystal/Powder (CuSO4.5H2O) - 24% Cu

Manganese Sulphate - Powder (MnSO4.H2O) - 30.5% Mn.

Let Us Sum Up

Due attention is required to improve the use efficiency of the expensive fertilizer resource. Different sources of fertilizers discussed in this presentations would help in improving the rice productivity .



Sustainable rice production through integrated nutrient management will require integrated strategies for the use of various sources of plant nutrients in conjunction with efficient soil, water and crop management practices.

chemical fertilizers as a component of inm in rice

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