Search

Aim: Nitrogen use efficiency (NUE) in subtropical cropping systems is low causing a large quantity of reactive N loss to the environment. However, the mechanisms and pathways of such losses are poorly understood. The objectives of the research were to quantify N volatilization rates and corresponding NUE in a biochar and nitrapyrin-treated cabbage field using N-control as well as a 15N-based approach. Methods: The treatments consisted of: N-control, urea alone, urea with nitrapyrin (UN), urea with biochar (UB), and urea with biochar and nitrapyrin (UNB). In each plot, 15N-labeled urea was applied in 1 m2 micro-plots to repeat the treatments. Results: The UNB had higher (p < 0.001) crop yields than other treatments by 29, 23 and 16% over the urea, UN and UB treatments, respectively, while the UN and UB were also higher than the urea alone. The estimated 15N-based NUE was higher (p < 0.01) in the UNB (40%) than in the urea alone (32%) but similar to the UN (36%) and UB (38%). The N-control based calculation overestimated NUE by 2–13% relative to the 15N-based approach. The UNB treatment reduced NH3 volatilization by 37, 22, and 33% over urea alone, UB and UN, respectively (p < 0.01). Post-harvest soil organic carbon (SOC) and total N were higher (p < 0.001) in the UNB and UB treatments than the other treatments. Conclusion: Our results with a subtropical crop suggest that biochar alone or co-applied with nitrapyrin improves NUE and mitigates NH3 volatilization while increasing SOC and TN contents. [ABSTRACT FROM AUTHOR]

Composting is a good option of solid waste recycling, but its use by the farmers is limited because of its low nutrient status. Our study has considered organic amendments to increase nutrient status of MSW compost. We prepared three types of amended compost by mixing 20% mustard oil cake (MOC) and 30% poultry manure (PM) or cowdung (CD) or sugarcane press mud (SPM) with 50% MSW compost. Trichoderma viridi inoculum was used to accelerate the composting process. Different amendments improved the nutrient level of MSW compost. A field experiment was conducted to measure the performances of amended MSW composts alone and with fertilizers on yield and nutrient content of brinjal (Solanum melongena) and soil fertility. The experiment was carried out at Bangladesh Agricultural University research farm having silt loam texture, 6.7 pH and 2.79% organic matter; the soil was Aeric Haplaquept under the order Inceptisols. There were 10 treatments consisting of chemical fertilizers (urea, TSP, MoP, gypsum & zinc sulphate) and four types of MSW compost (3 enriched and 1 unenriched). The nutrient status of soil had increased due to application of composts. Based on the results of fruit (edible portion) yield and N, P, K and S concentrations of brinjal, and soil nutrient availability, the mixture 50% fertilizers +10 t ha-1 of enriched compost (MSW + MOC + SPM in a ratio of 5:2:3) was found as the best treatment. Results of this study have significant value in fertilizer management strategies for brinjal cultivation in sub-tropical countries. [ABSTRACT FROM AUTHOR]

Shallow tube well (STW) water, often contaminated with arsenic (As), is used extensively in Bangladesh for irrigating rice fields in the dry season, leading to potential As accumulation in soils. In the current study the consequences of arsenic from irrigation water and direct surface (0–15 cm) soil application were studied under field conditions with wetland rice culture over 2 years. Twenty PVC cylinders (30-cm length and 30-cm diameter) were installed in field plots to evaluate the mobility and vertical distribution of soil As, As mass balance, and the resulting influences on rice yield and plant-As concentration in Boro (dry season) and transplanted (T.) Aman (wet season) rice over the 2-year growth cycle. Treatments included irrigation-water As concentrations of 0, 1 and 2 mg L−1 ( Boro season only) and soil-As concentrations of 10 and 20 mg kg−1. Following the 2-year cropping sequence the major portion (39.3–47.6%) of the applied arsenic was retained within the rooting zone at 0–15 cm depth, with 14.7–19.5% of the total applied As at the 5–10 cm and 10–15 cm soil depths compared to 1.3–3.6% at the 35–40 cm soil depth. These results indicate the relatively low mobility of applied As and the likely continued detrimental accumulation of As within the rooting zone. Arsenic addition in either irrigation water or as soil-applied As resulted in yield reductions from 21 to 74 % in Boro rice and 8 to 80 % in T. Aman rice, the latter indicating the strong residual effect of As on subsequent crops. The As concentrations in rice grain (0.22 to 0.81 µg g−1), straw (2.64 to 12.52 µg g−1) and husk (1.20 to 2.48 µg g−1) increased with increasing addition of As. These results indicate the detrimental impacts of continued long-term irrigation with As-contaminated water on agricultural sustainability, food security and food quality in Bangladesh. A critical need exists for the development of crop and water management strategies to minimize potential As hazard in wetland rice production. [ABSTRACT FROM AUTHOR]

A study was made over 3 years to find out an optimum rate of Zn application for the maize–mungbean–rice cropping system in a calcareous soil of Bangladesh. Zinc application was made at 0, 2 and 4 kg ha−1 for maize (cv. Pacific 984, Thai hybrid) and at 0, 1 and 2 kg ha−1 for rice (cv. BRRI dhan33), with no Zn application for mungbean (cv. BARI mung5). Effect of Zn was evaluated in terms of yield and mineral nutrients contents (N, P, S and Zn). All the three crops responded significantly to Zn application. The optimum rate of Zn for the maize–mungbean–rice cropping system was found to be 4–0–2 kg ha−1 for the first year and 2–0–2 kg ha−1 for subsequent years particularly when mungbean residue was removed, and such rates for mungbean residue incorporation being 4–0–1 and 2–0–1 kg ha−1, respectively. For all crops, the Zn and N concentrations of grain were significantly increased with Zn application. For the case of grain-S, the concentration was significantly increased for maize and mungbean, but it remained unchanged for rice. The grain-P concentration on the other hand tended to decrease with Zn application. For maize, the grain-Zn concentration increased to 27.0 μg g−1 due to 2 kg Zn ha−1 treatment from 16.5 μg g−1 for Zn control and at higher Zn rate (4 kg Zn ha−1) the increment was very minimum. Another field experiment was performed over 3 years on the same soil to screen out maize varieties for Zn efficiency. Of the eight varieties tested, the BARI maize 6 and BARI hybrid maize 3 were found Zn in-responsive (Zn efficient) and the others Zn responsive (Zn-inefficient). [ABSTRACT FROM AUTHOR]

A study was undertaken to determine the effects of different concentrations of arsenic (As) in irrigation water on Boro (dry-season) rice (Oryza sativa) and their residual effects on the following Aman (wet-season) rice. There were six treatments, with 0, 0.1, 0.25, 0.5, 1, and 2 mg As L-1 applied as disodium hydrogen arsenate. All the growth and yield parameters of Boro rice responded positively at lower concentrations of up to 0.25 mg As L-1 in irrigation water but decreased sharply at concentrations more than 0.5 mg As L-1. Arsenic concentrations in grain and straw of Boro rice increased significantly with increasing concentration of As in irrigation water. The grain As concentration was in the range of 0.25 to 0.97 µg g-1 and its concentration in rice straw varied from 2.4 to 9.6 µg g-1 over the treatments. Residual As from previous Boro rice showed a very similar pattern in the following Aman rice, although As concentration in Aman rice grain and straw over the treatments was almost half of the As levels in Boro rice grain. Arsenic concentrations in both grain and straw of Boro and Aman rice were found to correlate with iron and be antagonistic with phosphorus. [ABSTRACT FROM AUTHOR]