Indicators of soil quality and crop productivity assessment at a long-term experiment site in the lower Indo-Gangetic plains

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.     

Comparison of New Ultrasonic Digestion Approaches for Plant Matrices in the Analysis of Trace Metals by Inductively Coupled Plasma–Optical Emission Spectroscopy Analysis: Contrast with USEPA Method 3050B

An ultrasonic method using two approaches, A and B, along with a reference Environmental Protection Agency (EPA) Method 3050B [i.e., a mixture of 30 mL of nitric acid–hydrochloric acid–hydrogen peroxide–water (HNO₃-HCl-H₂O₂-H₂O)] were contrasted for leaching of a plant matrix. The trace metals were arsenic, cadmium, cobalt, chromium, copper, mercury, manganese, nickel, lead, selenium, and zinc (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se and Zn) and quantified by ICP-OES followed by an investigation into residue formation and the impact of digestion time. Approach B was the most accurate and precise with percent recoveries ranging between 99 and 120%, whereas ultrasonic approach A and the USEPA method 3050B gave similar results with poor accuracies and precisions. In the optimization of the digestion time using approach B, the total metal recovery was fairly the same over a period of 120 min except for Cr and Cu, which showed slight variations.     

Dynamics of macronutrients in olive leaves

The study aims to track the dynamics of the olive leaf nitrogen (N), phosphorus (P) and potassium (K) for five olive varieties under drip irrigation in farmer's fields in central Morocco. Leaf sampling was done every month from May 2014 to April 2015. Leaf macronutrients contents showed variation over time. Olive leaves have maintained the same N content throughout the study period indicating a continuing olive uptake of nitrogen. Higher leaf P absorption was observed during flowering and fruit magnification periods indicating the important P needs of olive during these periods. Olive leaf K levels were higher from September to December indicating the high K needs of olive. No variety effect was revealed on the leaf N, P and K contents. Very highly significant differences were found between the leaf N and K levels measured at different sampling periods. The leaf P concentration was statistically equal in all measuring periods.     

Screening of Wheat Genotypes for Boron Efficiency

Several sand culture and field experiments were conducted to screen out a number of Bangladeshi wheat varieties and advanced lines for boron (B) efficiency against Thai B efficient (‘Fang 60’) and inefficient (‘SW41’ and ‘E12’) varieties. Performances of wheat genotypes were evaluated with respect to flag leaf B concentration, pollen viability, grain set index, and grain yield. Wheat genotypes responded differently to boron deficiency. Pollen viability was found to be 67% in ‘Kanchan’, 35% in ‘Gourab’, 80% in ‘Sourav’, 90% in ‘Fang 60’, and 25% in ‘SW 41’ when B was not added. Pollen viability of all varieties was above 90% when B was applied. Based on grain set index and leaf B concentration, ‘Sourav’ was found to be the moderately B efficient variety. Thus, ‘Sourav’ can be regarded as a breeding material for development of new wheat varieties for tolerance to B deficiency.     

Assessment of Biodegradation of Oleandrin during Co-composting of Nerium oleander L. Wastes

ABSTRACT

Variations in the levels of the highly toxic oleandrin molecules were studied during composting of Nerium oleander L. waste mixed with clippings of the grass Pennisetum clandistenum L. The thermophilic phase is characterized by a rise in temperature, which reached 70°C. After 150 days of co-composting, the C/N ratio was 11, the pH was 8, the NO₃^?/NH₄⁺ ratio was greater than 1 and overall decomposition reached 70%. During the successive stages of co-composting, oleandrin concentrations were monitored by HPLC. The relative abundance of oleadrin was 26.84% at T0 with 10% abatement during the first month and 90% after two months (stabilization phase), reaching 100%, i.e., total removal after 90 days of co-composting (maturation phase). The biodegradation of the toxic substance was largely attributed to the activity of actinomycetes and fungi. The germination index of lettuce and watercress seeds exceeded 50% after 90 days and reached 95% after 150 days, confirming that the final compost was mature, stable, and free from phytotoxicity in spite of the highly poisonous starting material.     

Chemically Modified Crop Residues as a Low-Cost Technique for the Removal of Heavy Metal Ions from Wastewater

Batch adsorption experiments were carried out to evaluate the effect of type of crop residues and chemical pretreatment solutions on the removal efficiency of heavy metal ions at different concentrations of synthetic wastewater solutions. Rice straw, cotton stalks, and maize stalks were pretreated with different solutions (i.e., sulfuric acid, oxalic acid, sodium hydroxide, and distilled water as the control treatment) in order to increase their metal-binding capacity. Results indicated that cotton stalks were the best biosorbent material according to their efficiency in removal of heavy metal ions. Sodium hydroxide was the best chemical pretreatment method for stimulating the biosorption capacity of crop residues. Ions of Pb²⁺ had the highest biosorption ratio among all competitive ions, whereas Mn²⁺ ions had the lowest. The removal efficiency decreased as the concentration of heavy metal ions increased in aqueous solutions. Sorption equilibrium isotherms could be described by the Langmuir model in most cases, whereas an isotherm of S shape was observed in other cases, which did not follow the Langmuir isotherm model. In conclusion, cotton stalks pretreated with sodium hydroxide could be used as an efficient technique for wastewater remediation prior to irrigation due to its low-cost, little processing, and high biosorption capacity.     

Assessment of genetic divergence in salt tolerance of soybean (<Emphasis Type="Italic">Glycine max</Emphasis> L.) genotypes

A large number of soybean (Glycine max L.) genotypes of diverse growth habit and adaptive characters were used in the experiment. Soil salinity-induced changes in nine morpho-physiological characters of 30-day-old seedlings of 170 soybean genotypes were compared in the study. The first and second principal components (PC) of principal component analysis (PCA) results accounted for 97 and 2.5%, respectively, of the total variations of soybean genotypes. The variation for the first PC was composed mainly of relative total dry weight (DW), relative shoot dry weight, as well as petiole dry weight. There were four clusters distinguished in the cluster analysis. The genotypes in cluster IV performed better in respect to relative total dry weight and relative shoot dry weight and hence having salt tolerance. The genotypes clusters III performed very poorly and those of clusters II and I were moderate to poor. D2 analysis indicated that the clusters differed significantly from each other. Discriminant function analysis (DFA) again asserts strongly that more than 92% of the genotypes were correctly assigned to clusters. Both PCA and DFA confirmed that the relative total DW followed by shoot and petiole DW were the major discriminatory variables, and the root DW were the secondary important variables to distinguish genotypes into groups. In this study, multivariate analyses were used in identifying the soybean genotypes of desirable traits for salt tolerance.     

The Cytological Status of Plants Regenerated from Shoot-Meristem Culture of Pisum sativum L

The cytological status of plantlets regenerated from shoot apical meristems of Pisum sativum was investigated. Chromosome counts in root apices of in vitro regenerated plants showed a preponderance of diploid cells. Moreover, the karyotypes of root-tips from plants derived from culture and from normal plants were basically the same. Topics such as the treatment of chromosomal armlength data, simple statistical comparison of samples derived from normal and regenerated plants are discussed.     

Comparison of leaf and pod disease reactions of beans (Phaseolus vulgaris L.) inoculated by different methods with strains of Xanthomonas campestris pv. Phaseoli (Smith) dye

Summary Common blight disease in beans (Phaseolus vulgaris), caused by the bacterium Xanthomonas campestris pv. phaseoli, reduces crop yield and seed quality. Information is needed on the variation of leaves and pods disease reaction to strains of the bacterium after different inoculation methods. Phaseolus vulgaris cultivars Red Kidney Charlevoix, GN Harris, GN 1140, and GN Emerson were inoculated with three different strains of Xanthomonas campestris pv. phaseoli at two inoculum concentrations (10⁸ and 10⁶ bacterial cells/ml) using water soaking, multiple needle, and razor blade inoculation on leaves, and razor blade scratch, dissecting needle, and razor blade cut inoculation on pods. Differential cultivar disease reactions of leaves, pods, or both to the bacterial strains were observed in some cases. Significant interactions among cultivars, inoculation methods, strains, and inoculum concentrations (leaves) were found. A rapid leaf chlorosis developed 6 to 7 days after inoculation. Strains of bacteria did not show specificity in inducing this reaction, but rapid leaf chlorosis was associated with high inoculum concentration and with the water soaking and multiple needle methods. Another experiment was conducted to count the number of living bacterial cells deposited in the leaf tissue after inoculation by different methods. The number of bacteria deposited by water soaking or multiple needle was higher than that deposited by razor blade.Published as Paper No. 8584, Journal Series, Nebraska Agricultural Experiment Station. Research was conducted under Project No. 20–36.