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Evaluation of the Soil Fertility Status for Fertilizer Recommendations for Wetland Rice

M. A. Rahman
Ministry of Agriculture, GoB, Dhaka

Anwar Iqbal
PSO(Soils)
Bangladesh Agricultural Research Council, Farmgate, Dhaka-1215

N. I. Bhuiyan
CSO and Head
Soil Chemistry Division, BRRI, Joydebpur. Gazipur, Bangladesh

S. M. Nabi
PSO
Horticulture Research Centre, BARI, Gazipur.

Abstract/ Executive Summary:

Evaluation of the soil fertility status of the Khadimnagar soil series was made for the purpose of recommending fertilizers for wetland rice cultivation. Soil samples were analysed using the Agroservices International (ASI) methods, Results obtained were related to the critical levels of different plant nutrients and finally treatment combinations were formulated for a greenhouse study on BRI4 rice. Laboratory analysis showed that, soils of Khadimnagar series are deficient in NPKSCa and B, while through sorption studies this particular soil was found to be below the critical level in respect of P,K,S, Zn and Cu. The plant dry matter yield data reveled that the Khadimnagar soil is deficient in NPK and S but not in Zn. The study suggests that, the predicted optimum treatment and the critical levels of nutrients determined by the ASI methods were not applicable for wetland rice soils of Bangladesh.

Keywords: Fertilizer, Soil fertility, Wetland Rice, Fertilizer recommendation

Location: BRRI, Joydebpur, Gazipur.

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soil fertility

Objectives:

i) To characterize soils with respect to their nutrient status and absorption capacities,

ii) To relate soil analytical result with the critical level of different nutrients, and

iii ) To formulate fertilizer recommendation for wetland rice

Methodology:

Bulk soil samples (50 kg each) were collected from the Khadimnagar soil series from a depth of 0-20 cm. Air dried samples were crushed, passed through a 2.0 mm sieve and mazed throughly. One kg portions of each bulk sample were used for laboratory analysis. Description of the collected soil samples is given. The soil samples were analyzed using the modified sodium bicarbonate extraction procedure (ASI method). In the ASI method 0.25 N NaHCO₃ + 0.01 M EDTA=0.01 N NH₄F are used for analysis of P,K, Cu, Fe, mn and Zn. Analysis was done for NH₄-N, extractable acidity, Ca and Mg using In KCI extraction procedure. Analyzed of S and B were done using the Ca (H₂PO₄)2 extraction procedure. The pH and organic C content were also determined. Standard laboratory procedures were followed for sorption studies. The sorption studies were accomplished by adding various rates of the elements in solution to a soil sample. The amount of solution added was sufficient to completely saturate the soil sample and leave an excess standing on the sample. This produced anaerobic condition in samples for a few hours. The sample containers were left open to air dry which required about three days. This system allowed the clement to react with the soil under moisture regimes ranging from complete saturation to air drying and simulated in short period of time, the kind of reaction which might be expected to take place under field conditions. A greenhouse study was conducted with BRI 14 rice. Except for N and Mo, the optimum treatment was determined based on laboratory analytical data. Sorption curves for P. K, Cu, Mn, Zn, S and B were constructed when the extracted value from the original soil sample was below three times the deficiency critical level of the elements. Then to bring the level to three times the deficiency critical level the required amount obtained from the sorption curve was added. The Ca/Mn ratio was maintained within the range of 1.2 to 6.2 and Mn/K ratio was maintained within 1.6 to 14 by adding Ca. Mn or K into the soil samples. The entire work including the greenhouse study was done at the BRRI Central Station. A 500g priori or the air dried soil sample was taken in a polyethylene bag and as per treatment, an amount of nutrient solution was added to it. All the treatments were established in a similar way. One day after addition, the nutrients were thoroughly mixed with the soil by repeated shaking. The soil was then put into plastic pots and puddled adding required amounts of pond water. The pots were placed in the greenhouse in a randomized complete block design with 4 replications. After 3-4 days of puddling, 15 rice seedlings (BR 14) ( 14 day old) were transplanted ill each pot. After 10 days, the number or plants per pot was thinned to 10 . After thinning, 0.02g of Furadan 3G was added to each pot as a plant protection measure. Water was added regularly to maintain a wetland condition one plant protection measure. Water was added regularly to maintain a wetland condition one half of the total of planting. The position of the pots were rearranged several times in the greenhouse to minimize micro-environmental effects. After six weeks, the plants were harvested at the ground level. The plant samples were over dried at 70⁰C (+ 5⁰C) for two days and their dry weights were recorded.

Source of Information: Bangladesh J. Agri. 1997, 22: 41-46

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The predicted optimum treatments for the Khadimnagar soil formulated on the basis of laboratory studies did not behave as real optimum treatments under the greenhouse condition. The critical levels or different nutrients in soil by the ASI method appeared to he not applicable for wetland rice soils or Bangladesh. The present approach or fertility evaluation can he used as an effective tool for wetland rice culture utter ascertaining precisely the critical levels or different nutrients. Further studies will he needed before going for generalized recommendations.

Knowledge Management: Journal