M. A. Saleque

Yield and phosphorus efficiency of some lowland rice varieties at different levels of soil-available phosphorus

Abstract A field experiment was conducted on an Aerie Haplaquept soil to study the effect of phosphorus (P) deficiency in soil on the P nutrition and yield of five modern varieties of rice, viz., Purbachi, BR1, BR3, BR14, and BR29, popular with the rice farmers of Bangladesh. Soil‐available P in the different plots of the experimental field varied widely, from 2.8 to 16.4 ppm. This plot to plot variation in soil‐available P content resulted from differences in the total amounts (0 to 480 kg ha‐1) of P the plots had received over a period of 8 years in a long‐term P fertilizer trial conducted previously in the same field. Phosphorus deficiency in soil drastically reduced the grain yield of all the rice varieties. In severely P deficient plots, where soil‐available P was around 3 ppm, the yield was less than 1 ton ha‐1 while in plots containing an adequate P level, i.e., >6 ppm, the yield was more than 41 ha‐1. Rice yield increased linearly with an increase in soil P content up to 6 ppm, and the highest gra...

Long‐Term Integrated Nutrient Management for Rice‐Based Cropping Pattern: Effect on Growth, Yield, Nutrient Uptake, Nutrient Balance Sheet, and Soil Fertility

Abstract A 7‐year‐long field trial was conducted on integrated nutrient management for a dry season rice (Boro)–green manure (GM)–wet season rice (T. Aman) cropping system at the Bangladesh Rice Research Institute Farm, Gazipur during 1993–1999. Five packages of inorganic fertilizers, cow dung (CD), and GM dhaincha (Sesbania aculeata) were evaluated for immediate and residual effect on crop productivity, nutrient uptake, soil‐nutrient balance sheet, and soil‐fertility status. Plant height, active tiller production, and grain and straw yields were significantly increased as a result of the application of inorganic fertilizer and organic manure. Usually, the soil‐test‐based (STB) fertilizer doses for a high‐yield goal produced the highest grain yield of 6.39 t ha−1 (average of 7 years) in Boro rice. Application of CD at the rate of 5 t ha−1 (oven‐dry basis) once a year at the time of Boro transplanting supplemented 50% of the fertilizer nutrients other than nitrogen (N) in the subsequent crop of the cropping pattern. A positive effect of GM on the yield of T. Aman rice was observed. Following GM, the application of reduced doses of phosphorus (P), potassium (K), sulfur (S), and zinc (Zn) to the second crop (T. Aman) did not reduce yield, indicating the beneficial residual effect of fertilizer applied to the first crop (Boro rice) of the cropping pattern. The comparable yield of T. Aman was also observed with reduced fertilizer dose in CD‐treated plots. The total P, K, and S uptake (kg/ha/yr) in the unfertilized plot under an irrigated rice system gradually decreased over the years. The partial nutrient balance in the unfertilized plot (T1) was negative for all the nutrients. In the fertilized plots, there was an apparent positive balance of P, S, and Zn but a negative balance of N and K. This study showed that the addition of organic manure (CD, dhaincha) gave more positive balances. In the T4c treatment at 0–15 cm, the application of chemical fertilizers along with the organic manures increased soil organic carbon by (C) 0.71%. The highest concentration of total N was observed with T4c followed by T4d and T4b, where CD was applied in Boro season and dhaincha GM was incorporated in T. Aman season. The sixfold increase in soil‐available P in T4b‐, T4c‐, T4a‐treated plots was due to the addition of CD. Dhaincha GM with the combination of chemical fertilizer helps to mobilize soil‐available P by 3 to 6 ppm. The highest amount of soil‐available S was found in T4c‐ and T4a‐treated plots. It was 2.5 times higher than that of the initial soil. The application of CD and dhaincha GM along with chemical fertilizers not only increased organic C, total N, available P, and available S but also increased exchangeable K, available Zn, available iron (Fe), and available manganese (Mn) in soil.

INFLUENCES OF PHOSPHORUS DEFICIENCY ON THE UPTAKE OF NITROGEN, POTASSIUM, CALCIUM, MAGNESIUM, SULFUR, AND ZINC IN LOWLAND RICE VARIETIES

A field experiment was conducted to study the effect of phosphorus (P) deficiency on the mineral nutrition of five modern, high-yielding rice varieties, Purbachi, BR1, BR3, BR14, and BRRIDHAN29. The available P in the soils of different plots of the experimental field varied from 2.8 to 16.4 mg kg−1. Such a wide range of available P in the different plots resulted from differences in the amounts of P (0 to 480 kg ha−1) applied over a period of 8 years during a previous long-term P fertilizer trial in the same field. The relationship among the P, potassium (K), and magnesium (Mg) concentrations in rice straw and grain in a soil P deficiency situation were especially noteworthy. The K concentration in rice straw was negatively correlated with the P concentration (r = −0.42 to −0.60), but in the case of grain the coefficient of correlation between P and K concentration were positive (r = 0.60 to 0.74). There was a strong positive relationship between the P and Mg concentration in grain (r = 0.70 to 0.97). These results suggest that the P deficiency in soil does not only affect the P nutrition of rice, but may also affect the uptake of other nutrients, especially that of K and Mg. The concentration of P in rice straw or grain increased or decreased, obviously, with an increase or decrease in the available P level in soil. Of interest, however, was the observed effect of the P concentration on the concentrations of nitrogen (N), K, and Mg in rice straw and grain.

Effect of moisture and temperature regimes on available phosphorus in wetland rice soils

Abstract A laboratory experiment was conducted to evaluate the effects of water and temperature regimes on availability of soil phosphorus (P). Four soil samples with variable levels of available P collected from a long‐term P frequency trial were incubated under two moisture regimes, continuous waterlogging (CWL) and alternate wetting and drying (AWD) at 20°C and 30°C temperature for 90 days. The samples were extracted with 0.5M NaHCO3 for available P determination after incubation. Increase in temperature increased available P content and this increase was more prominent in CWL conditions. Available P in all the soils tested was higher under CWL than AWD conditions, however, the increase in available P due to CWL environment was more pronounced in soils with higher available P.

Variety-Specific Nitrogen Fertilizer Recommendation for Lowland Rice

Abstract Nitrogen (N) is the most limiting nutrient for rice in tropical Asian soils, and almost every farmer has to apply the costly N fertilizer to get a desirable yield of rice. Modern high yielding rice varieties may have differences in accumulating and using N from soil and applied fertilizer. An experiment with 10 rice genotypes was conducted to estimate their efficiency to use inherent soil N, applied fertilizer N, and to predict optimum N input for a desirable yield. The genotypes were grown at two N levels: 0 and 130 kg N ha−1. Under the N control plots, the grain yield of rice varied from 3.26 to 4.63 t ha−1, and the yield range in the N treated plots was 4.69–6.24 t ha−1. The tested rice genotypes varied in straw N concentration (0.45%–0.73%) and grain N concentration (0.81–1.53%). Therefore, the N requirement among the tested rice genotypes varied from 9.02 to 13.78 kg t−1 in the N control plots and from 10.93 to 15.66 kg t−1 in the N-treated plots. Despite their modern plant characteristics, the tested genotypes significantly varied in N use efficiency and apparent N recovery. The BR4839-17-5-2-2-HR5 gave agronomic N use efficiency of 18.38 kg grain/kg applied N, whereas in BR6209-16-3 it was only 5.15 kg/kg. The apparent N recovery of the BR4839-17-5-2-2-HR5 was 34.85%, which was as low as 11.25% in BR6209-16-3. The calculated N fertilizer dose for the observed yield varied from 78 to 113 kg ha−1, compared to a flat soil test-based recommended dose. For a target yield of 6.0 t ha−1, the required N fertilizer for the advance line BR4839-17-5-2-2-HR5 was 91 kg ha−1, compared to 109 kg N ha−1, which was required for the variety BRRI Dhan 29. The study shows that the N fertilizer recommendation for rice would be more cost-effective if the genotypic efficiency in N use of rice at biochemical level is taken into account.

Response of wetland rice to potassium in farmers’ fields of the Barind tract of Bangladesh

Abstract Six trials were conducted in the dry and wet seasons on potassium (K)‐deficient Barind soils (Aeric Haplaquept) to evaluate the response of rice to potassium (K) fertilizer. The application of 30 kg K ha‐1 significantly increased rice grain yields at all the test locations. In some cases, grain yield increased consistently up to 120 kg ha‐1 of applied K. Rice yield responded quadratically to K application. The calculated maximum K doses were 114 kg ha‐1 for the dry season and 165 kg ha‐1 for the wet season. The calculated optimum doses of K application were 100 kg ha‐1 and 147 kg ha‐1 for the dry season and wet season, respectively. Application of K fertilizer increased K content only in the straw, but not in the grain. The K use efficiency of wetland rice at 30 kg K level was 16.7 kg grain kg‐1 applied K in the dry season and 10.0 to 33.3 kg grain kg‐1 applied K in the wet season. The K uptake by rice was higher in the dry season than in the wet season. The average apparent K recovery at 30 kg K...

Quantity–Intensity Relationships and Potassium Buffering Capacity of Four Ganges River Floodplain Soils

Ganges river floodplain soil extends from Nepal through India to Bangladesh, which is a good niche for rice–rice and rice–wheat cropping systems in Asia. Application of potassium (K) fertilizer does not give any yield benefits to rice and wheat grown on most of the Ganges floodplain soils in Bangladesh. Understanding of soil K dynamics in this soil is important for the development of K management for rice–rice and rice–wheat cropping pattern in the region. Four Ganges floodplain soils, Sara clay loam, Ghior clay loam, Gopalpur silt, and Ishurdi silt loam, were evaluated for labile K (ΔK0), K intensity ( ), change in solution (ΔK), equilibrium exchangeable K (EKo), magnitude of conversion of solution K to exchangeable K (α), and potential buffering capacity of K (PBCK). The four soils had exchangeable K [ammonium acetate (NH4OAc extracted)] of 0.17 to 0.43 cmol kg−1, with the least in Ishurdi silt loam and the most in Ghior clay loam. The greatest ΔK0 (−0.81 cmol kg−1) was observed in Gopalpur silt, and the least (−0.25 cmol kg−1) was found in Ishurdi silt loam soil. The four soils exhibited equilibrium values of 0.007 to 0.021 (mmol L−1)1/2, with the least in Ishurdi silt loam and the greatest in Gopalpur silt soil. The greatest EK0 (0.66 cmol kg−1) was observed in Ghior clay loam, and the least (0.21 cmol kg−1) was in Ishurdi silt loam. Four soils were also different in the magnitude of conversion of solution K to the exchangeable K (α), being the greatest (67%) in Ghior clay loam and the least (25%) in Gopalpur silt soil. The tested soils were similar in PBCK [36.80–39.39 cmol kg−1/(mmol L−1)1/2]. The characteristics of ΔK0, , ΔK, EKo, α, and PBCK in the studied soils varied with the depth. Future research is needed to calibrate the characteristics of K dynamics for soil fertility management and to predict how long a nonresponsive soil can meet crop K demand for rice–rice and rice–wheat cropping systems.

Effect of organic and inorganic fertilizers and rice straw on carbon sequestration and soil fertility under a rice–rice cropping pattern

ABSTRACT Rice–fallow–rice, the dominant cropping system in Bangladesh, has received little attention regarding soil organic carbon (SOC) changes through organic amendments. Understanding the contributions of organic amendments in C sequestration is important for carbon budgeting. This study determined the effect of organic amendments on CO2 emission to the atmosphere and C sequestration in soil. A series of field experiments in five consecutive rice seasons were conducted during 2010–2012 at the research farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Bangladesh, using five treatments – control, cow dung (CD), poultry manure (PM), rice straw (RS) and soil test-based fertilizer (STB). The carbon application rate from CD, PM and RS was 2 t C ha−1 season−1. Carbon dioxide production from rice fields was measured through NaOH absorption followed by HCl titration. The difference in the amount of cumulative CO2 evolution and SOC accretion between the control and organic treatments gave apparent C balance and C sequestration. CD, PM and RS contributed to the positive soil nutrient balance. Application of CD, PM and RS resulted in 36, 28 and 37% loss of applied C through emission, respectively. The application of organic C through RS, CD and PM accounted for 10, 30 and 49% sequestration, respectively. There were 34, 23 and 53% unaccounted amounts of applied C from CD, PM and RS, respectively, which may be attributed to anaerobic decomposition where CO2 was not produced, or escaping of the produced CO2 through aerenchyma channels to the leaf surface. Poultry manure was found to be efficient in increasing carbon and other nutrients in soils, and contributed to a higher grain yield of rice compared to RS and CD. Due to STB fertilization, microbial activities might be enhanced and favored better growth of root biomass, which contributed to slight sequestration of SOC in the rice–rice cropping system.

System productivity, nutrient use efficiency and apparent nutrient balance in rice-based cropping systems

A 2-year field experiment was conducted to assess system productivity, nutrient use efficiency and apparent balances of phosphorus (P) and potassium (K) in diversified rice-based cropping systems at Gazipur, Bangladesh. Four cropping systems: wheat–fallow–rice, maize–fallow–rice, potato–fallow–rice and mustard–fallow–rice in main plots and four nutrient combinations: NPK, NK, NP and PK in sub-plots were arranged in a split-plot design with three replications. Receiving the NPK treatment, all the component crops gave the highest yield, and omission of N from fertilizer package gave the lowest yield. The maize–rice system removed the highest amount of N (217 kg ha−1), P (41 kg ha−1) and K (227 kg ha−1) followed by wheat–rice, potato–rice and the least in mustard–rice system. The wheat–rice and maize–rice system showed negative K balance of –35.5 and –60.4 kg ha−1 in NPK treatment, while potato–rice system showed a positive K balance of 31.0 kg ha–1 with NPK treatment. The N, P and K uptake and apparent recovery by the test crops may be used for site-specific nutrient management. The K rates for fertilizer recommendation in wheat and maize in Indo-Gangetic plain need to be revised to take account for the negative K balance in soil.

Evaluation of two concepts of fertilization for wheat in a calcareous soil of Bangladesh

Two popular concepts of soil fertilization, basic cation saturation ratio (BCSR) and sufficiency level of available nutrients (SLAN), were tested on a calcareous soil (Aeric haplaquept) during 1995-1996 at the Bangladesh Rice Research Institute (BRRI) Regional Station Rajshahi using wheat as a test crop. According to BCSR concept the soil was deficient in potassium (K) and according to SLAN concept it was deficient in phosphorus (P), respectively. Potassium dose of 120 kg ha-1 [to attain 2% saturation of total cation exchange capacity (CEC) according to BCSR] along with other two doses (0 and 60 kg K ha-1) and P dose of 50 kg ha-1 (to attain available P at sufficiency level) along with other two doses (0 and 100 kg P ha-1) were compared in a randomized complete block design. The application of 50 kg P ha-1 significantly increased plant height, spikes m-2, grains per spike, grain and straw yields of wheat over 0 kg P ha-1 with or without K but increasing P dose from 50 to 100 kg P ha-1 did not give additional yields. The agronomic parameters and yields were not affected significantly by K application. Similar results were also observed in nutrient content and nutrient uptake. Thus, SLAN concept appeared as an effective tool for fertilizer recommendation for the calcareous soil while BCSR gave no apparent result there.