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241.
Irrigation with wastewater provides the opportunity to solve the problems of its disposal, reuse and water conservation. Freshwater, differentially diluted wastewater and undiluted wastewater (hereafter called wastewater) were used to grow wheat in sandy loam soil under fertilized and unfertilized conditions at the experimental farm of Bangladesh Agricultural University, Bangladesh. Fresh groundwater and wastewater of Mymensingh municipality were used to irrigate a wheat field for three consecutive years to examine the effects of wastewater application on soil properties. In this study, the properties of wastewater-irrigated soil were compared with freshwater-irrigated soil. The application of wastewater reduced the bulk density of the surface soil by 1.92% and augmented the porosity by 5.89%. The unsaturated hydraulic conductivity and water retention capacity of the soil were improved under wastewater irrigation. Soil pH increased due to wastewater application but decreased, to a smaller extent, due to fertilizer application. Soil electrical conductivity (EC) increased both with wastewater and with fertilizer application; both parameters changed significantly in the 0–20 cm soil layer. However, at the deeper layers, they were not affected by wastewater application. The organic carbon (C) and total nitrogen (N) level of the soils were higher under wastewater irrigation than under freshwater-irrigated soil. The organic C increased by 23.93% under wastewater irrigation in the top 20 cm soil layer. The N content of the soil showed similarities with the organic C contents. Available P and S concentrations were greater in the soil irrigated with wastewater compared with the soil irrigated with freshwater. The exchangeable cations – sodium (Na), potassium (K), calcium (Ca) and magnesium (Mg) – also increased significantly with wastewater application. Thus, farmers are advised for irrigation with municipal wastewater to ease pressure on freshwater and to improve soil fertility.  相似文献   
242.
Organics, biological, and inorganic fertilizers play a crucial role for improving crop yield and soil properties. Accordingly, we assessed their impact on yield, microbial activities, and transformations of carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) in soils under a 12-year-old intensively cultivated rice (Oriza sativa L.), mustard (Brassica juncea L.), sesame (Sesamum indicum L.) system with sole inorganic (NPK); NPK + farmyard manure (NPKF); NPK + green manure (NPKG) (Sesbania sesban L.), and NPK + green manure + bio-fertilizer (NPKGB) (Azotobacter chroococcum+ pseudomonas putida) treatments in sub-tropical India. The system yield was much higher with NPKF (23%) and NPKGB (18%) than that with NPK. Organic supplementation had a favorable influence on soil microbial biomass C (Cmic), N (Nmic), and activities of extracellular enzymes. Results of principal component and multiple regression analyses showed significant influence of Cmic on system yield (R2 = 91, = 0.001) and S availability (R2 = 62, = 0.001). Similarly, mineralizable N and acid phosphatase could predict significantly soil available N (R2 = 85, = 0.001) and P (R2 = 51; = 0.001), respectively. Results thus indicated that integrated nutrient management (NPKF/G) improved system yield, nutrient accumulation, and microbial activities in soils.  相似文献   
243.
Field experiments were carried out to assess the effect of nutrient management on soil properties and available micronutrients using Soil Test Crop Response (STCR) based targeted yield equations under a six-year old pearl millet-wheat cropping system. After six years, results showed that soil pH and bulk density decreased, while cation exchange capacity and organic carbon increased in farmyard manure (FYM) as compared to control and nitrogen, phosphorus and potassium (NPK) treated plots in both surface and sub-surface soil depths. Higher values of available zinc (Zn) (1.54 mg kg?1) and iron (Fe) (5.68 mg kg?1) were maintained in FYM+NPK treated plots, while higher values of manganese (Mn) (6.16 mg kg?1) and copper (Cu) (1.07 mg kg?1) were found in FYM alone at surface soil as compared to sub-surface soil. This study demonstrated the importance of application of FYM in improving soil properties and maintaining micronutrients availability in soil and their uptake by wheat for sustainable crop production.  相似文献   
244.
Six isoenergetic diets were formulated as follows: fish meal (FM) 700 g kg–1 (control, C), FM 300 g kg–1 + soy protein concentrate 300 g kg–1 (SPC), FM 300 g kg–1 + enzyme‐treated SPC 300 g kg–1 (ESC), FM 170 g kg–1 + soy protein isolate 300 g kg–1 (SPI), FM 160 g kg–1 + enzyme‐treated SPI 300 g kg–1 (ESI) and FM 150 g kg–1 + conglycinin 300 g kg–1(CG). Forty fish (3.9 g) were randomly distributed into each of eighteen 300‐L tanks, fed twice daily until satiation for 8 weeks. The final body weight, specific growth rate and condition factor did not show significant differences among the fish fed with diets C, SPC, ESC and ESI (> .05). The survival was significantly lower in fish fed with diets SPI and CG. Feed efficiency was significantly higher in fish fed with diets SPC and C than in fish fed with other diets (< .05). There were no significant differences in nutrients retention efficiencies in fish fed with diets C, SPC, ESC and ESI. A significantly higher phosphorus retention efficiency in fish fed with soymilk protein diets resulted in lower phosphorus discharge to the environment (< .05). These results suggest that the soymilk proteins can comfortably replace 570–770 g FM kg–1 diet of red sea bream juvenile, which will ensure significant ecological benefits through reducing phosphorus load to the environment.  相似文献   
245.
246.
Strawberry cultivation is not popular in Bangladesh due to the unpredictable climatic conditions and lack of proper cultivars. Using somaclonal variation, several new promising selections were generated and evaluated for their flowering and fruiting ability, adaptability and sustainability. To induce variation, plants were regenerated using various tissue culture techniques. Our results suggested that a high concentration of BAP in culture medium successfully resulted in the induction of somaclonal variation. Among the tissue culture techniques adopted in this study, meristem culture was most effective for induction of somaclonal variation. Twenty five putative somaclones with better horticultural features were subsequently selected and field evaluated for three clonal generations. Several of the selections reverted back to their original phenotype within 2–3 vegetative propagations. Three of the stable selections were distinct from each other in terms of fruit and other horticultural characters, and have potential for commercial cultivation in Bangladesh.  相似文献   
247.
Frequency and depth of irrigation play crucial role in crop yield and use efficiency of water resource. To test this hypothesis a field study was carried out in November to January of 2001-2002 to 2003-2004 on a sandy loam (Aeric haplaquept) for quantifying the frequency and depth of irrigation on growth, curd yield (CY) and water use pattern of cauliflower (Brassica oleracea L. var. botrytis). Four irrigation frequencies depending on the attainment of cumulative pan evaporation (CPE) values of: 25 (CPE25), 31(CPE31), 38 (CPE38) and 45 (CPE45) mm were placed in main-plots, with three depth of irrigation (IW) of 35 (IW35), 30 (IW30) and 25 (IW25) mm in sub-plots. Water use efficiency (WUE), net evapotranspiration efficiency (WUEET) and irrigation water use efficiency (WUEI) were computed. Marginal water use efficiency (MWUE) and elasticity of water productivity (EWP) were calculated using the relationship between CY and seasonal actual evapotranspiration (SET). A continuous increasing trend in growth parameters, yield and WUEI was recorded with the increase in SET from CPE45-IW25 to CPE31-IW30. However with further increase in SET the same decreased up to CPE25-IW35 regime. Highest WUE and WUEET obtained under CPE38-IW35 regime where SET value was 5% lower than the status of SET under CPE31-IW30. This study confirmed that critical levels of SET needed to obtain maximum curd yield or WUE, could be obtained more precisely from the knowledge of MWUE and EWP.  相似文献   
248.
Three photoperiods (12L:12D, 16L:8D and 24L:0D) were used to investigate the growth performance and stress response in red sea bream, Pagrus major (body weight 200–400 g). Fish were fed a commercial diet to apparent satiation, two times a day for 8 weeks. Fish exposed to a 24L:0D photoperiod showed a significantly higher weight gain (%) than those exposed to other photoperiods (P<0.05). The best specific growth rate and feed conversion efficiency were achieved at 24L:0D and 16L:8D, without significant differences among them. Although fish exposed to 16L:8D showed a significantly higher plasma level of cortisol than those exposed to other photoperiods in the third week, there was no major variation in the cortisol level among the treatments either at the sixth week or at the end of this study. There were no significant differences either in the haematocrit level or the plasma levels of glucose, total cholesterol and total protein among the treatments during this study. The results revealed that the growth performance of red sea bream reared from 200 to 400 g can be stimulated significantly using a continuous (24L:0D) photoperiod without any measurable significant stress response in fish.  相似文献   
249.
Deterioration of soil quality under resource-intensive modern agriculture in the face of global climate change poses a huge risk to food security. Because of the complex nature, estimators of soil quality often rely upon a limited set of soil attributes, along with statistical data reduction techniques, for developing quality indices, whilst overlooking biological aspects and regional climatic variability. This study screened the most suitable soil quality indexing approaches for a rice-oilseed-based cropping system in the lower Indo-Gangetic plains (IGP). For this, surface soil samples (0–15 cm) were collected from an ongoing long-term fertilizer experiment with a rice-mustard-sesame cropping system in the IGP. The following treatments were assessed for their effect on soil quality: T1-control, T2-NPK (recommended NPK doses), T3-NPKG (NPK + in situ green manuring), T4-NPKGB (NPK + in situ green manuring + biofertilizer) and T5-NPKF (NPK + farm yard manure FYM). We found that total organic carbon (TOC), β-glucosidase, CaCl2 extractable S, alkaline KMnO4 oxidizable N, activity of urease, amidase enzyme and mean weight diameter (MWD) were sensitive key indicators of soil quality. The NPKF treatment maintained the highest soil quality status (0.80–0.91), both under productivity and environmental protection goals, owing to the availability of decomposable carbon. Regression analysis showed a better agreement of equivalent rice yield with expert opinion (EO; R2 = 0.89) than principal component analysis (PCA; R2 = 0.76). Finally, we found that the expert opinion approach with the nonlinear scoring function was the best tool for soil quality assessment of the region.  相似文献   
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