Widespread Deficiencies of Sulfur,Boron, and Zinc in Indian Semi-Arid Tropical Soils: On-Farm Crop Responses

On-farm studies were conducted during 2002–2004 to determine fertility status, including sulfur (S) and micronutrients, and crop response to fertilization on farmers' fields in the semi-arid zone of India. Nine hundred-twenty four soil samples taken from farmers' fields, spread in the three districts of Andhra Pradesh (India), were analyzed for soil chemical fertility parameters. Results showed that samples were low in organic carbon (C), total nitrogen (N), and low to moderate in extractable phosphorus (P), but adequate in available potassium (K). Analyses of soil samples for extractable S and micronutrients was most revealing and showed that 73–95% of the farmers' fields were deficient in S, 70–100% in boron (B), and 62–94% in zinc (Zn). On-farm trials conducted during three seasons (2002–2004) showed significant yield responses of maize, castor, groundnut, and mung bean to the applications of S, B, and Zn. The yield responses were larger when S, Zn, and B were applied along with N and P. Applications of S, B and Zn also significantly increased the uptake of N, P, K, S, B, and Zn in the crop biomass. Results show widespread deficiencies of S, B, and Zn under dryland agricultural conditions; results also show that the nutrient deficiencies can be diagnosed by soil testing. It was concluded that the drylands in the semi-arid regions of India were not only thirsty (water shortage), but also hungry (nutrient deficiencies).     

Soil fertility in flooded and non-flooded irrigated rice systems

The lowland rice system in Asia makes a major contribution to the global rice supply and is often cited as an example of a sustainable system in which two or three crops of rice are grown in sequence under submerged conditions. However, water shortages are becoming critical in some regions for lowland rice cultivation; and there is high potential in exploring rice cultivation under moisture regimes that save water and also increase productivity. The objective of this article therefore is to analyze the consequences of switching growing of rice from flooded to aerobic conditions on soil fertility and its management. Fertility advantages of submerged rice include amelioration of chemical fertility, preferential accumulation of organic matter and improved availability of major, secondary and selected micronutrients, which contribute to the long-term maintenance of soil fertility and sustainability of the lowland rice system. However, the fertility problems under aerobic rice are better addressed with the crop as a component of a cropping system because continuous growing of aerobic rice in sequence does not seem sustainable due to complex, site-specific chemical and biological constraints.     

Extending results from agricultural fields with intensively monitored data to surrounding areas for water quality management

A 45% reduction in riverine total nitrogen flux from the 1980-1996 time period is needed to meet water quality goals in the Mississippi Basin and Gulf of Mexico. This paper addresses the goal of reducing nitrogen in the Mississippi River through three objectives. First, the paper outlines an approach to the site-specific quantification of management effects on nitrogen loading from tile drained agriculture using a simulation model and expert review. Second, information about the net returns to farmers is integrated with the nitrogen loading information to assess the incentives to adopt alternative management systems. Third, the results are presented in a decision support framework that compares the rankings of management systems based on observed and simulated values for net returns and nitrogen loading. The specific question addressed is how information about the physical and biological processes at Iowa State University’s Northeast Research Farm near Nashua, Iowa, could be applied over a large area to help farmers select management systems to reduce nitrogen loading in tile drained areas. Previous research has documented the parameterization and calibration of the RZWQM model at Nashua to simulate 35 management system effects on corn and soybean yields and N loading in tileflow from 1990 to 2003. As most management systems were studied for a 6 year period and in some cases weather had substantial impacts, a set of 30 alternative management systems were also simulated using a common 1974-2003 input climate dataset. To integrate an understanding of the economics of N management, we calculated net returns for all management systems using the DevTreks social budgeting tool. We ranked the 35 observed systems in the Facilitator decision support tool using N loading and net returns and found that rankings from simulated results were very similar to those from the observed results from both an onsite and offsite perspective. We analyzed the effects of tillage, crop rotation, cover crops, and N application method, timing, and amount for the 30 long term simulations on net returns and N loading. The primary contribution of this paper is an approach to creating a quality assured database of management effects on nitrogen loading and net returns for tile drained agriculture in the Mississippi Basin. Such a database would systematically extend data from intensively monitored agricultural fields to the larger area those fields represent.     

Comparative Evaluation of Inductively Coupled Plasma-Optical Emission Spectrometry and Colorimetry for Determining Phosphorus in Grain Samples

The inductively coupled plasma (ICP)-based method provides the opportunity to determine phosphorus (P) along with other major, secondary, micro and trace elements in plant materials. This study was conducted to compare and evaluate the relative efficacy of the inductively coupled plasma-optical emission spectrometry (ICP-OES) method with that of the colorimetric method using Skalar autoanalyzer, for determining P in 428 grain samples of eight diverse crops. The results on grain P analysis by the two methods, for individual as well as for all crop samples combined, showed that they were highly positively correlated (r varied from 0.84 to 0.98, p < 0.0001 for the eight crops, and R² for all crop grain samples was 0.9201, p < 0.0001). Moreover, the precision by the ICP method was similar to that determined by the Skalar method. Our results demonstrate that the ICP-OES method can be conveniently used for determining P along with other plant nutrient elements in grain samples of diverse crops.     

Soil and Plant Testing for Iron: An Appraisal

Iron (Fe) deficiency chlorosis in crops is common in high-pH calcareous soils. Soil and plant testing is routinely used for diagnosing iron (Fe) deficiency chlorosis in crops, with mixed results. This article presents an overview of the factors that influence soil and plant tissue testing results. It is clear that soil tests for Fe are dominantly influenced by soil pH, bicarbonate, and moisture regime rather soil test result per se. This is because the solubility of Fe is more regulated by soil pH and moisture regime. Plant tissue testing for Fe can complement the results of soil testing for Fe. But at times, especially in calcareous soils, total Fe in plant tissue is not related to Fe deficiency, but metabolically active Fe is better at diagnosing the occurrence of the disorder. A combined use of soil and plant tissue testing seems more helpful in diagnosing Fe deficiency chlorosis disorder in crops.     

Analytical Solutions of the Transient State Oxygen Diffusion Equation in Soils With a Production Term

Analytical solutions were developed to describe the nonsteady-state transport of oxygen from the atmosphere into the soil media. These analyses are based on diffusion theory for oxygen diffusion in soils when oxygen is being consumed, either at a constant rate or consumption rate varies with time due to the biological and chemical processes occurring continuously in the soil media. The transport equations, and the initial and boundary conditions are set up to represent a field situation. Analytical solutions are obtained to calculate transient oxygen concentrations in the soil profile. The quantity of oxygen that might diffuse into the soil from atmosphere at any time, t, also can be found by using this method. Comparison with published data is made, and reasonably good agreement is obtained between oxygen concentrations at different depths and times computed from the analytical solutions and those actually measured.     

Relationships of barley biomass and grain yields to soil properties within a field in the arid region: Use of factor analysis

Abstract

Understanding the variability of soil properties and their effects on crop yield is a critical component of site-specific management systems. The objective of this study was to employ factor and multiple regression analyses to determine major soil physical and chemical properties that influence barely biomass and grain yield within a field in the arid region of northern Iran. For this purpose, soil samples and crop-yield data were collected from 108 sites, at regular intervals (20×30 m) in a 5.6 ha field. Soil samples were analysed for total nitrogen (TN), available phosphorus (P_ava), available potassium (K_ava), cation-exchange capacity(CEC), electrical conductivity (EC), pH, mean weight diameter of aggregates (MWD), water-stable aggregates (WSA), field capacity volumetric (FC), available water-holding capacity (AWHC), bulk density (BD), and calcium carbonate equivalent (CCE). Results of the factor analysis, followed by regression of biomass and grain yield of barley with soil properties, showed that the regression equations developed accounted for 78 and 73% of the total variance in biomass and grain yield, respectively. Study of covariance analysis among soil variables using factor analysis indicated that some of the variation measured could be grouped to indicate a number of underlying common factors influencing barley biomass and grain yields. These common factors were salinity and sodicity, soil fertility, and water availability. The most effective soil variables to barley production in the study area identified as EC, SAR, pH, TN, P_ava, AWHC, and FC. In this study, factor analysis was effective to identify the groups of correlated soil variables that were significantly correlated with the within field variability in the yield of the barley crop. Our results also suggest that the approach can be applied to other crops under similar soil and agroclimatic conditions.     

Nitrogen and/or phosphorus fertilization effects on organic carbon and mineral contents in the rhizosphere of field grown sorghum

The effects of nitrogen (N) and/or phosphorus (P) fertilizers on the nutritional status in the rhizosphere were studied by monitoring throughout the growth period the concentrations of organic carbon (C), inorganic N, NaHCO₃ extractable P, exchangeable K, Ca, and Mg in sorghum (Sorghum bicolor L. Moench) down in an Alfisol field, and of all these elements except for extractable P, and exchangeable Ca in a Vertisol field in semi-arid tropical India. These concentrations were compared between the rhizosphere soil and bulk soil of sorghum grown in both fields.

Organic C content of the rhizosphere soil increased with plant age and was significantly higher than that in the bulk soil throughout the growth of sorghum, but it was not affected by the rates of N or P fertilizer. Inorganic N concentration in the rhizosphere soil was significantly higher than that in the bulk soil until maturity in sorghum. The content of available P in the rhizosphere soil was significantly higher than in the bulk soil after the middle of the growth stage. Its average concentration in the rhizosphere soil across growth stages was significantly higher than in the bulk soil, which contradicts the observation in many reports that there is a depletion of P in the rhizosphere soil. The concentration of three exchangeable cations, K, Ca, and Mg, showed different patterns in the rhizosphere and the bulk soils. The concentration of K was almost constantly higher in the rhizosphere soil than in the bulk soil, Ca concentration was not different between the two soils, and Mg concentration was significantly higher in the bulk soil than in the rhizosphere soil. The reasons for these discrepancies cannot be explained at present. The concentrations of these cations were not affected by the rate of N or P fertilizer except for Mg at a later growth stage. The differences between rhizosphere and bulk soils in Alfisol were similar to those in Yertisol with respect to the concentration of organic C, inorganic N, and exchangeable K and Mg.     

Diversity of entomopathogenic bacteria associated with the white grub, Brahmina coriacea

A survey of potato fields located in the south-eastern region of Himachal Pradesh (India) was carried out in order to find out the natural pathogens infecting the white grub, Brahmina coriacea. About 88 % population of the infected grubs were found to exhibit symptoms of natural bacterial infection during the years 2007–2008. Hence, we attempted to isolate and characterize the most potent bacteria for the management of B. coriacea and tested their insecticidal activity. In this study, ten different bacterial isolates belonging to genera Bacillus, Psychrobacter, Paracoccus, Paenibacillus, Mycobacterium, Staphylococcus and Novosphingobium were isolated from B. coriacea. Bacterial species were identified based on morphology, biochemical tests and homologies of 16S rRNA gene sequences. Pathogenicity tests for all isolated bacteria at 1.0 × 10⁸ cfu/ml of broth were performed on late first instar grubs. Among the bacteria tested, Bacillus cereus induced highest mortality level of 51.85 % within 7 days of treatment followed by Psychrobacter pulmonis (33.33 %), Bacillus psychrodurans (25.93 %), Bacillus pumilus (25.93 %), Paenibacillus tylopili (22.22 %) and Novosphingobium capsulatum (18.52 %). Mortality levels were further increased up to 100 % by B. cereus followed by 88.89 % by P. pulmonis after 30 days of treatment. Our results indicate that B. cereus, P. pulmonis, B. psychrodurans, B. pumilus, P. tylopili and N. capsulatum may be valuable biological control agents for white grubs, B. coriacea.     

Studies on some physico-chemical changes associated with fruit ripening in tomato (Lycopersicon esculentum mill.)

The fruits of two tomato varieties were analysed at five stages of maturity, viz. mature green, turning, pink, red and red ripe, for some physico-chemical changes associated with fruit ripening. Fruit weight and size, pericarp thickness, drymatter, ascorbic acid, sugars, protein, N, P, Zn, Fe, Mn and Cu contents were observed to increase with maturity and reached maximum or near maximum at red stage. The acidity was maximum at turning or pink stage and then decreased to a minimum level at red ripe stage. Varietal differences were present.