Amina Khatun
Rice Farming Systems Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
M. K. Quais
Rice Farming Systems Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
A. A. Begum
Agronomy Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
M. A. Saleque
Soil Science Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh
M. S. U. Bhuiya
Department of Agronomy, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh
Nitrogen rates, Rice, Grain yield, Yield components, Straw yield.
Bangladesh Rice Research Institute’s experimental farm, Gazipur
Crop-Soil-Water Management
Fertilizer, Rice
The field experiment was conducted at Bangladesh Rice Research Institute’s experimental farm, Gazipur located at 23059/ N latitude, 90024/E longitude during Boro 2009-10 (November-April) season. The site is about 35 m above the mean sea level and has a subtropical climate, which is strongly influenced by the southwestern monsoon. It belongs to agro- ecological zone (AEZ) number 28 known as Madhupur Tract. The average annual rainfall is 2000 mm with more than 80% of it occurring from mid-June to the end of September. The mean lowest temperature (150C) is observed in January and the highest (300C) in May. The soil of the experimental field is Chhiata clay loam, a member of the fine, hyperthermic Vertic Endoaquept. The initial soil chemical properties at 0-15 cm soil depth were: pH 6.1, organic matter 2.02%, total N content 0.07%, available phosphorus (P) 10.14 mg kg–1 (0.5 M NaHCO3 extracted), exchangeable potassium (K) 0.17 c-mol(+)/kg soil (Neutral 1.0 N NH4OAc extracted), available sulfur (S) 20 mg kg –1 [Ca(H2PO4)2 extracted], and available zinc (Zn) 2.8 mg kg –1( 0.01N HCl extracted). The soil of the experimental plot was moderately acidic in nature and poor in fertility status. Two rice varieties, BRRI dhan28 and BRRI dhan29 were studied under irrigated conditions during Boro (November–April) season. BRRI dhan28 is a short duration high yielding Boro variety (growth duration 140 days) and BRRI dhan29 is a long duration high yielding Boro variety (growth duration 160 days). The experiment was conducted in a factorial randomized complete block design with three replications. Treatments comprised of two factors viz. two rice varieties and six N rates. The two rice varieties were BRRI dhan28 and BRRI dhan29 and the six N rates were 0, 50, 100, 150, 200 and 250 kg ha-1. Rice seedlings (40-45 days old) were transplanted in the first week of January 2010 and the crop was harvested on 26 April (BRRI dhan28) and 9 May (BRRI dhan29) 2010. Two - three rice seedlings were transplanted at 20 cm x 20 cm spacing. Unit plot size was 5 m x 4 m. All plots were surrounded by soil levees 30 cm high to avoid mixing of N among the plots. After transplanting the seedlings, intercultural operations like weeding, irrigation and pest control operations were done as and when necessary. Nitrogen was applied as urea in three equal splits at 20, 35 and 50 days after transplanting (DAT) for BRRI dhan28 and 20, 35 and 55 DAT for BRRI dhan29. Phosphorus, K, S and Zn were applied as triple super phosphate, muriate of potash, gypsum and zinc sulphate, respectively, during final land preparation as basal dose. Optimum dose of N was determined by differentiating the N response equation (Colwell, 1994). Two equations were compared (i) Quadratic equation and (ii) Square root equation. The form of the quadratic equation is as follows: Y = a + bN + cN 2; Where Y was estimated grain yield (kg ha-1), N was applied nitrogen fertilizer (kg ha-1), a, b and c were regression coefficients. Estimation of yield and yield components- At maturity, the crop was harvested manually at ground level. However, 16 hills from each plot were harvested at the ground level for estimating total straw yield. Grain yield was adjusted to 14% moisture content after sun drying and straw yield was recorded as oven dry basis. The 16 hills were selected at random from each plot just before harvesting to estimate plant height and tillers numbers. The panicle numbers were determined from 16 hill samples at harvesting. The panicles from the 16 hills were threshed. The grains and sterile spikelets were separated by a seed sorter (Kiya Seisakusho LDT, model 1973, Tokyo, Japan). After separation, the grains and sterile spikelets were counted by an automatic counter (Nagoya, model DC 1-0, Japan). Then the grain numbers per panicle and 1000 grain weight were measured at 14% moisture and sterility (%) were calculated by following standard procedures as described by (Yoshida et al., 1976). Rice plants from 5 m2 area from the middle of each plot were harvested at the ground level and threshed. The grains were dried in sun, winnowed, weighed and the yield was adjusted to 14% moisture content and expressed as t ha-1 using the following formula: Adjusted weight = W x (100 - M 1)/(100 - M 2) x 100; Where, W is the fresh weight of grains and M1 and M2 are the fresh and adjusted moisture percents of grains, respectively. Sterility was computed by dividing the number of unfilled spikelets by the total number of spikelets (filled grains + unfilled spikelets) and was expressed as percentage as follows: Sterility (%) = (unfilled spikelets/unfilled spikelets+filled grains) x 100; Analysis of variance (ANOVA) of the measured parameters was performed and the treatment means were compared using Duncan’s multiple range test (DMRT) at the 5% level of probability (Gomez and Gomez, 1984). The yield and yield components were analyzed by ordinary least squares linear regression as done by Dawe et al. (2000).
The Agriculturists 14(2): 48-60 (2016)
Journal