Proton nuclear magnetic resonance spectroscopy based investigation on propylene glycol toxicosis in a Holstein cow

Background

It is unknown which metabolites are responsible for propylene glycol (PG)-induced toxicosis, and a better understanding of the underlying mechanisms explaining incidences of abnormal behaviour of dairy cows fed PG is therefore needed.

Methods

The study included three cows of which one developed PG toxicosis. In order to investigate how the metabolism of PG differed in the cow developing toxicosis, proton nuclear magnetic resonance (NMR) spectroscopy was applied on ruminal fluids and blood plasma samples obtained before and after feeding with PG.

Results

PG toxicosis was characterized by dyspnea and ruminal atony upon intake of concentrate containing PG. The oxygen saturation of arterial blood haemoglobin and the oxygen pressure in arterial blood decreased along with the appearance of the clinical symptoms. NMR revealed differences in plasma and ruminal content of several metabolites between the cow responding abnormally to PG and the two control cows.

Conclusion

It is concluded that PG-toxicosis is likely caused by pulmonary vasoconstriction, but no unusual metabolites directly related to induction of this condition could be detected in the plasma or the ruminal fluid.     

Effect of sewage sludge and ammonium nitrate on wheat yield and soil profile inorganic nitrogen accumulation 1

The beneficial effect of sewage sludge in crop production has been demonstrated, but there is concern regarding its contribution to nitrate (NO₃) leaching. The objectives of this study were to compare nitrogen (N) rates of sewage sludge and ammonium nitrate (NH₄NO₃) on soil profile (0–180 cm), inorganic N [ammonium nitrate (NH₄‐N) and nitrate nitrogen (NO₃‐N)] accumulation, yield, and N uptake in winter wheat (Triticum aestivum L.). One field experiment was established in 1993 that evaluated six N rates (0 to 540 kg·ha^‐1·yr^‐1) as dry anaerobically digested sewage sludge and ammonium nitrate. Lime application in 1993 (4.48 Mg ha^‐1) with 540 kg N ha^‐1·yr^‐1 was also evaluated. A laboratory incubation study was included to simulate N mineralization from sewage sludge applied at rates of 45, 180, and 540 kg N ha^‐1·yr^‐1. Treatments did not affect surface soil (0–30 cm) pH, organic carbon (C), and total N following the first (1994) and second (1995) harvest. Soil profile inorganic N accumulation increased when ≥270 kg N ha^‐1 was applied as ammonium nitrate. Less soil profile inorganic N accumulation was detected when lime was applied. In general, wheat yields and N uptake increased linearly with applied N as sewage sludge, while wheat yields and N uptake peaked at 270 kg N ha^‐1 when N was applied as ammonium nitrate. Lime did not affect yields or N uptake. Fertilizer N immobilization was expected to be high at this site where wheat was produced for the first time in over 10 years (previously in native bermudagrass). Estimated N use efficiency using sewage sludge in grain production was 20% (average of two harvests) compared to ammonium nitrate. Estimated plant N recovery was 17% for sewage sludge and 27% for ammonium nitrate.     

Detection of nitrogen and phosphorus nutrient status in bermudagrass using spectral radiance

Nitrogen (N) and phosphorus (P) are two of the most limiting nutrients for crop production. Because of this, continued interest focuses on improving N‐and P‐use efficiency. Spectral radiance measurements were evaluated to identify optimum wavelengths for dual detection of N and P status in bermudagrass (Cynodon dactylon L.). A factorial arrangement of treatments (0, 112, 224, and 336 kg N ha^‐1 and 0,29, and 58 kg P ha^‐1) was applied to an established bermudagrass pasture for further study using a randomized complete block design. A wide range of spectral radiance measurements (276–831 nm) was obtained from each plot using a PSD 1000 Ocean Optics fiber optic spectrometer. The resulting spectra were partitioned into 10‐nm bands. Added indices were generated to test for correlation of N and P content with spectral radiance. The 435‐nm band (430–440 nm) was found to be independent of N and P treatment, and as a covariate, significantly decreased residual error. Using 435 nm as a covariate, it was found that biomass, N uptake, P uptake, and N concentration could be predicted using 695/405. No index reliably predicted bermudagrass forage P concentration. Spectral radiance has the potential to be used for predicting N and P nutrient status, but further work is needed to document response in different environments.     

Nitrogen accumulation efficiency: Relationship between excess fertilizer and soil‐plant biological activity in winter wheat

The point at which nitrogen (N) applied approaches 100% recovery in the soil once plant and microbial sinks have been saturated has not been determined in winter wheat (Triticum aestivum L.) production systems. In dryland winter wheat, subsoil accumulation has not been found to occur until N rates exceed that required for maximum yield. Many conventional N rate experiments have not properly evaluated subsoil N accumulation due to the lack of equally spaced N rates at the high end of the spectrum over which accumulation is expected to occur. Therefore, the objectives of this study were to (i) determine when soil profile accumulation efficiencies reach 100% in continuous winter wheat production and (ii) to evaluate the potential for nitrate‐nitrogen (NO₃ ^‐N) leaching in continuous winter wheat when extremely high rates of fertilizer N are used. Two field experiments (T505 and T222) were conducted for two years using ten N rates (preplant‐incorporated) ranging from 0 to 5376 kg N ha¹. No additional preplant fertilizer was applied in the second year. Following the first and second year wheat harvest, soil cores were taken to 2.4 m and bulk density, ammonium‐nitrogen (NH₄‐N) and NO₃‐N were determined. Crop N‐use efficiency (NUE) (N uptake treated ‐ N uptake check/rate applied) and soil profile inorganic N accumulation efficiencies (NAE) [net inorganic N accumulation in the soil profile/(fertilizer applied ‐ net N removed in the crop)] changed with fertilizer rate and were inversely related. Priming (increased net mineralization of organic N pools when low rates of fertilizer N are applied) may have occurred since increased NUE was observed at low N rates. The highest N‐accumulation efficiencies were at N rates of 168 and 448 kg ha^‐1 in experiments T505 and T222, respectively. At both T222 and T505, no subsoil accumulation of NH₄‐N or NO₃‐N beyond 100 cm was observed for any of the N treatments when compared to the 0‐N check, even when N rates exceeded 448 kg ha^‐1.     

Relationship Between Coefficient of Variation Measured by Spectral Reflectance and Plant Density at Early Growth Stages in Winter Wheat

ABSTRACT

The use of by-plot coefficient of variation (CV) has not been evaluated in precision agricultural work. This study evaluated the relationship between CVs determined from normalized-difference vegetative index (NDVI) sensor readings, plant population, and sensing direction on NDVI values. Randomly selected plots, measuring 1 m² (2003) and 3 m² (2004), were established for this study. Plots in 2004 were divided into three 1 m² subplots with, 0 and 120 kg ha^?1 fall-applied N, and 80 kg ha^?1 topdress nitrogen (N). Sensor reading of subplots were taken at Feekes 5 and 7 using the Green Seeker hand-held sensor. Results showed that the relationship between vegetative RI (RI_NDVI) and harvest RI (RI_Harvest) improved with increasing CV values. The prediction of RI_Harvest was improved when CV was integrated into the RI_NDVI calculation. RI_Harvest can be better predicted with RI_NDVI when the CV of spectral radiance measurements is used in the RI_NDVI equation.     

CHANGES IN RESPONSE INDICES AS A FUNCTION OF TIME IN WINTER WHEAT

Nitrogen (N) responsiveness of crops can change with time as it is strongly influenced by in-season environmental conditions. This study was conducted to determine the relationship of N responsiveness using a response index (RI) as a function of time at five locations (Efaw, Stillwater, Lake Carl Blackwell, Perkins and Lahoma, Oklahoma) over a three-year period. Subplots of 4 m² were established at each experimental site that employed a randomized complete block design. Normalized Difference Vegetation Index (NDVI) readings were taken using a Greenseeker (NTech Industries, Inc., Ukiah, CA, USA) handheld sensor at various growth stages. The N responsiveness (RI_NDVI) was determined as the ratio of NDVI readings from a non-N limiting strip and the farmer practice. Then, RI was plotted against days where growing degree days (GDD = (T_min + T_max)/2—4.4°C) were > zero (DGDD > 0). At all sites, RI_NDVI increased with advancing stage of growth. Excluding Perkins 2005 and Stillwater 2006, the relationship between RI_NDVI and DGDD > 0 was positive and highly correlated. When the number of days from planting to sensing where DGDD > 0 was less than 60, it is unlikely that a reliable estimate of RI_NDVI could be obtained since values were all small (close to 1.0), consistent with limited growth at the early stages of growth. Averaged over years and sites for all growth stages, the correlation of RI_NDVI and RI_Harvest was positive and increased up to the Feekes 9 growth stage. Our results further suggested that once RI_NDVI is collected, it should be adjusted using the Equation RI_NDVIadj = RI_NDVI × [1.87/(DGDD > 0 ? 0.00997) + 0.5876].     

Does phosphite,a reduced form of phosphate contribute to phosphorus nutrition in corn (Zea mays L.)?

Although fungicidal properties of phosphite have been recognized, its use as a fertilizer-P is still being debated. The objective of this study was to evaluate the effect of foliar-applied phosphite (HPO₃^?2) on the growth and yield of corn (Zea mays L.). Traditional fertilizer-P was also applied to compare the efficacy of phosphite. Dry matter yield, grain yield, and tissue P concentrations (grain, leaf, and stem) were evaluated in two field and two greenhouse studies in Oklahoma for 2 years. A commercial phosphite solution which contains 200?g P kg^?1 was sprayed at the rate of 2.34?L ha^?1 at different growth stages. Foliar phosphite did not increase dry matter and grain yield. In general, P concentrations in the grain, leaf, and stem were unaffected regardless of number of applications. Farmers should take with caution while using phosphite as a fertilizer to correct P deficiency for corn production.     

Economic feasibility of site-specific optical sensing for managing nitrogen fertilizer for growing wheat

A site-specific nitrogen fertilizer application system that uses optical reflectance measurements of growing wheat plants to estimate N requirements has been developed. The machine enables unique applications of liquid N fertilizer at a grid level of 0.37 m². To achieve widespread adoption, the precision application system must be efficient enough to overcome the cost advantage of pre-plant applications of anhydrous ammonia (NH₃) relative to top-dress applications of either dry or liquid N sources on growing wheat. The objective of this research is to determine if the system is more profitable than conventional methods. Data from on-farm N fertilizer experiments were collected across three years and nine locations in the Southern Plains of the U.S.A. Net returns were calculated for each of eight treatments. The site-specific precision system was competitive economically, but it was not unambiguously superior to the conventional alternatives because it could not overcome the cost advantage of NH₃ pre-plant N sources relative to the cost of applying urea-ammonium nitrate (UAN) during the growing season. The value of the precision system is sensitive to the price of UAN relative to the price of NH₃.