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Study of Nitrogen Use Efficiency and Yield of Rice Influenced by Deep Placement of Nitrogen Fertilizers

R.S. Rea
Department of Agriculture, Texas State University, San Marcos, USA

M.R. Islam
Department of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

M.M. Rahman
Department of Soil Science, Bangladesh Agricultural University, Mymensingh, Bangladesh

K. Mix
Department of Agriculture, Texas State University, San Marcos, USA

Abstract/ Executive Summary:

Continuous increase of nitrogen fertilizer use adversely affecting the soil health as well as the environment. It necessitates the systematic study of the impact of nitrogen (N) fertilizer use-reduction on crop yield. In this article, the effects of deep placement of nitrogen fertilizers on nitrogen use efficiency (NUE) and yield of rice variety “BRRI dhan46” were investigated and compared for three N formulations: urea super granule (USG), NPK briquettes and prilled urea (PU). The experiment was conducted in randomized complete block design (RCBD) with eight N treatments replicated three times. The treatments were applied by varying doses (0, 52, 78 and 104 kg ha^-1) of nitrogen fertilizers in a known identical soil and weather condition. Applications of PU, USG and NPK briquettes exhibited significant differences on yield attributes of rice. Results revealed maximum grain yield of 6.391 t ha^-1 (54% increases over control) for the dose USG 104 kg ha^-1 which is statistically similar to the dose USG 78 kg ha^-1 and NPK briquettes 104 kg ha^-1. The deep placement of USG and NPK briquettes enhanced both the recovery of applied N and N use efficiency compared to broadcast application of prilled urea. However, USG 78 kg ha^-1 showed maximum apparent N recovery, N use efficiency, gross margin and marginal benefit-cost ratio. Thus, an application of 78 kg ha^-1USG can be recommended for profitable cultivation of rice variety BRRI dhan46.

Keywords: Apparent nitrogen recovery, Marginal benefit-cost ratio, Nitrogen use efficiency, Prilled urea, Urea super granule.

Location: Soil Science Field Laboratory of Bangladesh Agricultural University, Mymensingh,

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Rice, Fertilizer

Objectives:

To study the NUE, grain yield, straw yield, apparent nitrogen recovery (ANR) and marginal benefit cost ratio for different doses to evaluate optimum dose.

Methodology:

Experimental site, weather, soil and variety The experimental site is located at Soil Science Field Laboratory of Bangladesh Agricultural University, Mymensingh, 24.75ºN latitude and 90.5ºE longitude, elevation 18m above the sea level and is located in the agroecological zone (AEZ) of the Old Brahmaputra Floodplain. The average temperature, rainfall and relative humidity were respectively 26.4ºC, 190.2 mm and 84.5%. Since some of the attributes such as soil pH, total nitrogen in soil, available phosphorus and exchangeable potassium reportedly affect NUE, it is important to quantify those attributes of experimental site. The selected field soil was a typical rice growing silt loam soil. The amount of total nitrogen in the soil was 0.136%, available phosphorus 3.16 ppm, exchangeable potassium 0.095% and the pH 6.07. BRRI dhan46, a high yielding variety of rice was used as the test crop in this experiment. It is a transplant rice cultivar and matures after 150-155 days of transplanting with average dry yield 5.0-7.5 Mt ha^-1. Treatments The experiment was carried out with the following treatments: Fertilizer applications All treatments were controlled for N only and before application of N fertilizers, the water in the rice plots was drained. Nutrients P, K, S and Zn were provided according to soil test recommendations and typical production demands. All treatments received S (18 kg ha^-1) and Zn (3 kg ha^-1) from gypsum and zinc oxide. Treatments T1, T2, T3, T4 and T5, received P (25 kg ha^-1) and K (50 kg ha^-1) from TSP (Ca (H₂PO₄)2) and muriate of potash (KCl), respectively. Treatments T6, T7 and T8, P and K were supplied from NPK briquettes. The PU was applied in three equal splits. The first dose of PU was applied 10 days after transplanting (DAT), the second dose was added as top dressing at 35 DAT (active tillering stage) and the third dose was top dressed at 55 DAT (panicle initiation stage). USG and NPK briquettes were applied after 10 DAT. The USG and NPK briquettes were placed at 8-10 cm depth between four hills at alternate rows. Irrigation, weeding and other agronomic practices were done whenever necessary. Data collection and analysis method Data collected for analysis of variables were: plant height, effective tillers per hill, panicle length, grains panicle^-1 and 1000-grain weight, grain and straw yield of BRRI dhan46 were recorded. For determination of yield attributes five hills were selected and number of tillers per hill, number of filled and unfilled grains per panicle and thousand grain weight was measured. The above ground plant parts were segmented into different components as leaf, stem, leaf sheath and panicle and were dried in an oven for 72 hours at 70⁰C. After drying to14% moisture, the grain yield of rice was measured as metric ton ha^-1. The straw yield of rice was recorded as metric ton ha^-1 on sun dry basis. For determination of total nitrogen semi-micro Kjeldahl method of Bremner and Mulvaney was used. The NUE (kg grain yield increase kg^-1 N applied) was determined by the following formula: NUE = (GY+N– GY0N) / FN; Where, GY+N = grain yield in treatment with N application, GY0N = grain yield in treatment without N application and FN = amount of fertilizer N applied (kg ha^-1). The apparent N recovery was calculated by the following formula: ANR (kg ha^-1) = (UN+N - UN0N) /FN; where, UN+N is total N uptake (kg ha^-1) with grain and straw; UN0N is the N uptake (kg ha^-1) in control; FN is amount of fertilizer N applied (kg ha^-1). All the data were statistically analyzed by F-test and the mean differences were ranked by DMRT at 5% level (Gomez and Gomez, 1984). All collected data were subjected to MSTAT-C software package to perform analysis of variance (ANOVA).

Source of Information: SAARC J. Agric., 17(1): 93-103 (2019)

Article Link (Online Journal): DOI: https://doi.org/10.3329/sja.v17i1.42764

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Based on grain yield, the treatments may be ranked in the order of T3>T4>T6>T7>T5>T2>T8>T1. Deep placement of USG at the rate of 104 kg ha^-1 and at the rate 78 kg ha^-1 performed better in increasing grain yield of rice compared to PU and NPK briquette. Thus, the deep placement of N fertilizers demonstrated the most positive effect on grain yield.

Knowledge Management: Journal