Effect of Foliar Application of Phosphorus on Winter Wheat Grain Yield,Phosphorus Uptake,and Use Efficiency

ABSTRACT

One would expect foliar applied phosphorus (P) to have higher use efficiencies than when applied to the soil, but limited information is available concerning this. Experiments were conducted in 2002, 2003, and 2004 to determine the effect of foliar applications of P on winter wheat grain yields, P uptake, and use efficiency. Twelve treatments containing varying foliar P rates (0, 1, 2, and 4 kg ha^{? 1} in 2002 and 2003 and additional 8, 12, 16, and 20 kg ha^{? 1} in 2004) with and without pre-plant rates of 30 kg ha^{? 1} were evaluated. Foliar applications of P at Feekes 7 generally increased grain yields and P uptake versus no foliar P. Use efficiency was higher when P was applied at Feekes 10.54. Results from this study suggested that low rates of foliar applied P might correct mid-season P deficiency in winter wheat, and that might result in higher P use efficiencies.     

FERTILIZER RATE EFFECTS ON FORAGE YIELD STABILITY AND NUTRIENT UPTAKE OF MIDLAND BERMUDAGRASS

Our objectives were to document effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on forage yields and uptake of N, P, and K by Midland bermudagrass [Cynodon dactylon (L.) Pers.] on a Minco fine, sandy loam in southern Oklahoma. After six years of this long-term experiment, forage yield responses to fertilization were mixed and depended on year. Stability analysis indicated forage yields responded positively to N fertilization during favorable weather conditions but negatively during poor weather conditions. Application of 112 kg N ha^?1 provided the best yield stability and mean annual forage yield among treatments, 11.5 Mg ha^?1, across years. In years with near-average weather conditions, uptake of N, P, and K increased linearly with N application rate. Limited water holding capacity of the soil and high soil P and K may have contributed to the limited yield responses to fertilization in this semi-arid environment.     

Forage and Grain Yield Response to Applied Sulfur in Winter Wheat as Influenced by Source and Rate

ABSTRACT

Recently, environmental quality issues related to sulfur (S) have made it necessary to reduce its release into the atmosphere in wet or dry forms, which in turn might influence the S requirement of crops. It is anticipated that by 2020, S deposition will decrease by up to 30% in eastern portions of Oklahoma and by 15% throughout the remainder of the state. This change calls for frequent monitoring and evaluation of S nutrition in wheat and other crops. Experiments were conducted at Hennessey and Perkins research stations for a period of seven years starting in the fall of 1996, with the objective of assessing the effect of different levels of elemental and sulfate-S fertilizers on the grain and forage yields of winter wheat in Oklahoma. The experimental design was a randomized complete block with three replications. Four S rates, 0, 56, 112, and 224 kg S ha^{? 1}, were applied to the plots from 1996 to 2002 as CaSO₄. Another two rates, 56 and 112 kg S ha^{? 1}, were included in the trials beginning in 1998 using 92% elemental S. Gypsum, as a source of S for winter wheat, resulted in a greater yield than did elemental S in cases where S fertilizer sources were deemed significant. In six of 14 trials from 1996 to 2002, applied S as CaSO4 significantly increased wheat-grain yields. Observing significant grain and forage yield increases due to applied S was important, but the response was sporadic and unpredictable from one year to the next.     

Hierarchical Bayesian models for soil CO2 flux using soil texture: a case study in central Hokkaido,Japan

Hierarchical Bayesian (HB) methods are useful tools for modeling multifaceted, nonlinear phenomena such as those encountered in ecology, and have been increasingly applied in environmental sciences, e.g., to estimate soil gas flux from different soil textures or sites. We have developed a model of soil carbon dioxide (CO₂) flux based on soil temperature (T, 5 cm depth) and water-filled pore space (WFPS, 5 cm depth) using HB theory. The HB model was calibrated using a dataset of CO₂ flux measured from bare soils belonging to four texture classes in 14 upland field sites in a watershed in central Hokkaido, Japan, in the nonsnow-cover season from 2003 to 2011. The numerical software HYDRUS-1D was used to simulate daily WFPS, and the estimated values were significantly correlated with the measured WFPS (R² = 0.68, P < 0.001). Compared to a nonhierarchical Bayesian model (Bayesian pooled model), the CO₂ predictions with the HB model more accurately represented texture-specific observations. The simulation–observation fit of the CO₂ flux model was R² = 0.64 (P < 0.001). More than 90% of the observed daily data were within the 95% confidence interval. The HB model exhibited high uncertainty for high CO₂ flux values. The HB model calibration revealed differing sensitivity of CO₂ flux to T and WFPS in different soil texture classes. CO₂ flux increased with an increase in T, and it increased to a lesser degree with a finer texture, possibly because the clay and silt facilitated soil aggregation, thus reducing temperature fluctuations. WFPS values between 0.48 and 0.64 resulted in optimal conditions for CO₂ flux. The minimum WFPS value increased with an increase in clay content (P < 0.05). Although only a small number of soil types were studied in only one season in this study, the HB model may provide a method for predicting how the effects of soil temperature and moisture on CO₂ flux change with texture, and soil texture could be regarded as an upscaling factor in future research on regional extrapolation.     

Estimates of variance components and repeatability for total forage yield in rye: implications for breeding

Cereal rye (Secale cereale L.) is an important forage crop in the USA for stocker cattle (Bos sp.) production, thus making forage yield an important breeding objective for the crop. However, little information is known about the repeatability for forage yield in this crop. The objectives of this research were to: (i) estimate variance components for forage yield from long‐term variety trials, (ii) estimate the repeatability for forage yield and (iii) relate this to breeding strategies for increased forage yield in rye. Trials were conducted over 14 years where 97 USA open‐pollinated varieties (OPVs) were evaluated. Repeatability ranged from 0.57 to 0.86 when the data were analysed by year for the 3 years with significant genotype main effects. Possible explanations for the lack of significant genotype main effects are discussed. Practical implications of these findings indicate that the development of improved cultivars with greater forage yield will require improved methods of selection based on family performance rather than the current methods based primarily on single plant visual selection.     

Efficacy of anti-staphylococcal protein P128 for the treatment of canine pyoderma: potential applications

In this study, we demonstrate the antibacterial activity of P128 on Staphylococcus isolates responsible for canine pyoderma. Eighty seven swabs were collected from dogs suffering from pyoderma and subjected to antibiotic sensitivity test and 46 Staphylococcus strains were isolated and characterized. In-vitro antimicrobial susceptibility testing with P128 was done by Minimum Inhibitory Concentration (MIC) method as per CLSI guidelines. All the Staphylococci isolated from the dogs with pyoderma, although showed resistance to various antibiotics tested, were lysed by P128. Clinical efficacy of P128 was examined in 17 dogs with pyoderma by application of the P128 hydrogel twice daily for 8 days and the results indicated complete healing of all the lesions of all the dogs under treatment. Under the conditions of this study, P128 was found to be a potent convenient proteinaceous drug for the treatment of staphylococcal pyoderma in dogs.     

Bayesian calibration as a tool for initialising the carbon pools of dynamic soil models

The most widely applied soil carbon models partition the soil organic carbon into two or more kinetically defined conceptual pools. The initial distribution of soil organic matter between these pools influences the simulations. Like many other soil organic carbon models, the DAYCENT model is initialised by assuming equilibrium at the beginning of the simulation. However, as we show here, the initial distribution of soil organic matter between the different pools has an appreciable influence on simulations, and the appropriate distribution is dependent on the climate and management at the site before the onset of a simulated experiment. If the soil is not in equilibrium, the only way to initialise the model is to simulate the pre-experimental period of the site. Most often, the site history, in terms of land use and land management is often poorly defined at site level, and entirely unknown at regional level. Our objective was to identify a method that can be applied to initialise a model when the soil is not in equilibrium and historic data are not available, and which quantifies the uncertainty associated with initial soil carbon distribution. We demonstrate a method that uses Bayesian calibration by means of the Accept-Reject algorithm, and use this method to calibrate the initial distribution of soil organic carbon pools against observed soil respiration measurements. It was shown that, even in short-term simulations, model initialisation can have a major influence on the simulated results. The Bayesian calibration method quantified and reduced the uncertainties in initial carbon distribution.