Asian Journal of Soil Science and Plant Nutrition

Unfavorable ecosystems in Bangladesh are under intense pressure of crop production and climate change impact; although the relationships of indigenous soil nutrients ratios with crop performance are yet to be fully explored. Experiments were conducted under submergence and cold prone areas (agricultural ecological zone, AEZ-3), drought and cold prone areas (AEZ-26), non-saline tidal flood ecosystem (AEZ-13), char and saline prone ecosystem (AEZ-18) and haor ecosystem (AEZ-21) for evaluating rice grain yield with native nutrients ratios. Synergistic and antagonistic relationships were observed in different AEZ depending on indigenous nutrient ratios. The Ca:P and N:Zn ratios were playing significant negative role with rice yield in wet season. In dry season, P:K ratio was acting antagonistically in AEZ-18, AEZ-3 and AEZ-26 but K:Mg, Ca:Zn S:Zn P:Zn were playing synergistic role in the same localities. The C:K ratio was playing antagonistic role with dry season irrigated rice yield in AEZ-13 and AEZ-21. Dry season irrigated rice grain yield was 13-27% lower in AEZ-26 than others AEZ because of variations in negative ratios of nutrients. Application of 187-13-75-15-1.1, 174-27-19-840, 162-11-58-11-0, 180-24-14-15-4 and 144-36-5-3-0 kg/ha of N-P-K-S-Zn, respectively for Rangpur, Rajshahi, Barisal, Sonagazi and Habiganj improved dry season rice yield significantly in all AEZ except AEZ-18 compared to indigenous soil fertility. Soil separates showed variable relationships with indigenous nutrient ratios in different AEZ. It is concluded that indigenous soil nutrient ratios play a vital role in improving rice yield under unfavorable ecosystems.

Cotton production in Nigeria has been severely limited by low or blanket nutrient (especially nitrogen, N) input and poor crop management, involving use of low yielding varieties and sub-optimal plant spacing. Field experiment was conducted during the wet season (June-October) of 2013 at two locations within the Research Farm, College of Agriculture, Jalingo (longitude 11° 09’ and 11° 30’ East and latitude 8° 17’ and 9° 01’ North) to determine the (i) adaptability of three improved cotton cultivars to local climates, (ii) appropriate rate of N for optimizing cottonseed yield and (iii) optimal plant density for economic yield. The experiment was a 4 x 3 x 2 factorial arranged in a randomized complete block design (RCBD) replicated three times. The treatment combinations consisted of four nitrogen (N) rates (0, 120, 150, 200 kg ha^-1), three cotton varieties (Jalingo Local, Samcot-13, Sketch-8) and two plant densities [75 x 30 cm or 44,444 plants ha^-1 and 60 x 30 cm or 60,000 plants ha^-1]. Data were collected on plant height, boll weight, cottonseed yield, biological (biomass) yield and numbers of monopodial and sympodial branches. Data collected were subjected to analysis of variance using the StatView Software and LSD (Least Significant Difference Test) at the 5% level of probability was used for comparison of treatment means. Plant height, boll weight, cottonseed yield, biological yield, monopodial and sympodial branches increased significantly (P < 0.05) with N application. The growth and yield components of cotton were optimum at 150 kg Nha^-1. For cottonseed (lint and seed yield) yield per boll, Samcot-13 treated with 150 kg Nha^-1 was the best. Cottonseed yield was best at 150 kg Nha^-1 with Jalingo Local variety at 44,444 plants ha^-1 density. Therefore, Jalingo Local sown at 44,444 plants ha^-1 with application of 150 kg N ha^-1 as urea in two equal splits (21 and 50 DAS) is recommended in the study area.

Field experiments were conducted for two seasons during 2012-2013 at Hi-Tech-Horticulture unit, University of Agricultural Sciences, Dharwad,Karnataka, India to evaluate the effect of drip irrigation and fertigation levels on tomato hybrid STH-801 under polyhouse condition. Three drip irrigation regimes (40, 60 and 80% ETc) were based on crop evapotranspiration (ETc) that was computed using Class A pan evaporation data and three fertigation levels (50, 75 and 100% RDF) in the form of water soluble fertilizer were laid out in factorial RCBD design and replicated thrice with one absolute control (drip irrigation at 100% ETc and soil application of 100% RDF in the form of conventional fertilizer). Drip irrigation at 40% ETc gave higher TSS, ascorbic acid, titratable acidity, total phenol andlycopene content over 60 and 80% ETc. However, yield recorded by 60 and 80% ETc irrigation regimes were on par and significantly higher as compares to 40% ETc irrigation regimes. Fertigation at 100% RDF recorded maximum TSS, ascorbic acid, titratable acidity, total phenol, lycopene content and yield which was par with 75% RDF and significantly superior over 50% RDF. Application of fertilizers through fertigation in the form of water soluble fertilizer enhanced yield and quality of fruits as compared with soil application of conventional fertilizer.

Aim: To evaluate the heavy metal content of soil samples from Njere river bank.

Study Design: Soil samples were sourced from three different locations, upstream, midstream and downstream of the river bank.

Place and Duration of Study: Department of Chemistry, Michael Okpara University of Agriculture, Umudike, between June 2009 and December 2009.

Methodology: In each location, soil sample was collected from various points and pooled together. The soil samples were air-dried and used for Atomic Absorption Spectroscopy.

Results: Total Ni and Zn concentrations were below W.H.O standard in the upstream and midstream samples. Fe and Pb were not detected in the midstream and downstream samples. Soluble concentrations of Ni, Fe and Zn and exchangeable concentrations of Ni, Cd, Fe, Zn and Pb were below the standard.

Conclusion: The results reveal that the heavy metal contamination of the soil around the Njere river bank is very low. The soil can support production of healthy crops for food security in the area.

This study was aimed at assessing the microbial population and chemical components of paraquat treated soils. The soil samples were treated with the low (0.3 ml/L), recommended (0.6 ml/L) and high (0.9 ml/L) doses of paraquat respectively. Microbial and chemical assessments were carried out using standard procedures. The results of the study showed that, microbes such as Staphylococcus sp., Micrococcus sp., Pseudomonas sp., Escherichia coli, Bacillus sp., Actinomycetes bovis, Actinomycetes israeli, Streptomycetes sp., Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, Absidia corymbifera and Rhizopus stolonifer were found present in the paraquat treated soils of different doses with the control soil samples having most of the fungal species isolated. The application of the paraquat to the soils at different weeks after application (WAA) affected the microbes as most were found absent in some of the treated soil samples and this was proved by the result of the control soil samples. The organic matter and carbon contents of the paraquat treated soils were at the 4^th WAA had the significantly (P=.05) highest contents with 1.93%, 1.93% and 1.84% and 1.34%, 1.12% and 1.12% respectively whereas the pH of the soils was at 2^nd WAA the highest compared to those of the other soils at other WAA as well as the control soils. Different doses of paraquat at different WAA affect soil microbial populations as well as the chemical components of the soil. So, the effects of paraquat on soil microbial population and chemical components depended on the concentrations used and the duration of application. Since the fungi, bacteria and actinomycetes species identified in this study were sensitive to herbicide application, they may serve as a reliable indicator of the biological value of soils.