Pulverizing Soils for Laboratory Analysis

Soil-testing laboratories utilize a range of grinder types to pulverize soils for laboratory analysis. This study was conducted to evaluate the effects of soil particle diameter and laboratory subsample size on analysis variability on nitrate, Bray 1 extractable phosphorus (P), extractable potassium (K), and soil organic matter (SOM). Four soils collected for the Agricultural Laboratory Proficiency Program were pulverized using four types of commercial grinders and analyzed for particle-size distribution, P, and K. In a second study, soils were pulverized to pass sieves of 2.0, 1.0, and 0.50 mm and subsampled for P, K, and SOM. Results of the commercial grinders indicate a range in mean particle diameters from 0.15 to 0.60 mm, with the lowest for the grinder utilizing a hammer mill design. Sieve-size analysis results indicate that the coarsest 2.0-mm fraction had the largest variability for all soil analyses evaluated. Analyte variability decreased with decreasing sieve size. Mean Bray P, K, and SOM-LOI (Loss-on-Ignition) mean concentrations were not statistically significantly different across the sieve sizes evaluated. Laboratory analysis variability for extractable Bray P increased as subsample size was reduced.     

Removal of Vegetative Clippings Reduces Dissolved Phosphorus Loss in Runoff

Rainfall simulation was used to study the vegetative filter strip (VFS) conditions under which losses of total dissolved phosphorus (TDP) and dissolved reactive phosphorus (DRP) leaching occur. Boxes containing silt loam soil were planted with ryegrass and cut at two different intervals prior to simulated rainfall 14 days apart. Grass clippings were either removed or retained. During the second simulated rainfall, runoff TDP and DRP were greater for treatments cut the day before irrigation with clippings retained as compared to treatments cut the same day as irrigation with clippings retained. Removing clippings yielded the lowest mean TDP and DRP concentrations. Increasing the senesced vegetative surface area for contact with water, and the amount of time for leaching to occur, resulted in the greatest DRP loss. The VFS management implications should consider clipping removal or no or reduced mowing during the growing season followed by end-of-season removal to reduce DRP leaching losses.     

32P distribution in white radish roots at various fertilization rates

Abstract

The uptake and distribution of ³²P from labelled monocalcium phosphate by white radish (Raphanus Sativus) roots at five phosphorus fertilization rates were studied.

After on initial period of degradation (approximately 6 weeks), there is a sharp decline of phosphorus uptake. Graphical representation in Tables and Figures of the phosphorus distribution is presented.     

速补钙磷对白唇鹿发病率的影响

对65只白唇鹿在补饲过程中添加速补钙磷,结果表明补饲过程中添加速补钙磷的试验组与对照组相比,对白唇鹿异食癖,提高鹿茸产量、降低鹿软骨病骨质疏松、瘫痪等作用显著。平均每只鹿鹿茸产量增加139.5g。鹿软骨病、瘫痪下降1.48%、异食癖发病率降为零。鹿羔月体重平均增2.5kg。     

Management options to decrease phosphorus and sediment losses from irrigated cropland grazed by cattle and sheep

In southern New Zealand, grazing of forage crops is common practice to satisfy feed requirements of animals in winter when pasture growth is limited. This practice has been shown to cause soil physical damage and increased loss of surface water contaminants sediment and phosphorus (P) to water bodies. Strategies to mitigate the loss of sediment and P were trialled on a Pallic soil type (Aeric Fragiaquept) in the North Otago Rolling Downlands of New Zealand. All sites were irrigated and measurements were made of losses in overland and sub‐surface flow from intensive cattle or sheep grazed, winter forage crops, and sheep grazed pasture. Two mitigations (restricted grazing of crop to three hours and the application of aluminium sulphate) were assessed for their potential to decrease contaminant loss from cropland. Volumes of surface runoff and loss of total P, filterable reactive P and sediment showed significant differences (P < 0.05) between the control treatments (i.e. no mitigation) with cattle crop (88 mm surface runoff) > sheep crop (67 mm) > sheep pasture (33 mm). The contribution of irrigation water to overland flow water, as a result of saturation‐excess conditions, varied between treatments with more loss under cattle crop (20% of total) compared with sheep crop (15%) and sheep pasture (11%). These differences are probably an effect of soil physical condition and highlight the importance of accurate irrigation scheduling to keep soil moisture below field capacity. Restricted winter grazing and alum application after grazing significantly (P < 0.05) decreased P losses in surface runoff under cattle (from 1.4 to 0.9 kg P/ha) and sheep (from 1.0 to 0.7 kg/P/ha) grazed crop plots by about 30%. In cattle grazed plots, restricted grazing also decreased suspended sediments (SS) by 60%. The use of restricted grazing is suggested as a means of decreasing P and SS loss from grazed winter forage crops. The use of alum shows some promise for decreasing P losses, but requires further work to determine its long‐term effectiveness and use in other soils and management regimes.     

Effects of feeding and animal performance on nitrogen, phosphorus and potassium excretion by Holstein cows

Thirty‐four Holstein dry cows and 16 lactating cows were used in balance trials to identify the effects of feeding and animal performance on nitrogen (N), phosphorus (P) and potassium (K) excretion by dairy cows, and to develop prediction models for these excreta. Orchard grass silage, corn silage, alfalfa silage or timothy hay were offered to dry cows. Orchard grass silage or alfalfa silage, and concentrates were offered to lactating cows. In the statistical analysis, the independent variables were bodyweight (kg), dry matter (DM) intake (kg/day), milk yield (for lactating cows only, kg/day), water intake (free water plus water in feed, kg/day), intake (g/day) of N, P and K and dietary contents (% of DM) of crude protein, P and K. The dependent variables were N, P and K excretion (g/day) in feces and urine. In both dry and lactating cows, intake of N, P and K had large effects on corresponding excretion. The results indicated that a decrease in the intake of N, P and K could decrease the corresponding excretion. Further research by path analysis showed that K intake positively affected urinary N excretion in dry cows indirectly, through water intake and urine volume.     

Bone mineral changes in growing, pregnant and lactating cattle

Bone mineral content (BMC) was determined in one or two coccygeal vertebrae by dichromatic photon absorptiometry in two sets of cattle: A. This set consisted of six fattening bulls. Their increases of BMC and weights were closely correlated. However, BMC increased slightly more than weight. B. There were 28 cows in this set. BMC was measured during lactation and pregnancy. It was found that BMC increased during the dry period and decreased during early lactation. There were great individual variations in BMC, and the skeletal turnover seemed to be great.     

磷肥用量对甜玉米磷素吸收利用的影响

Understanding the phosphorus (P) absorption mechanism is the premise for high P utilization and high crop yield. In this study, the effects of different P rates (0, 37.5, 75, 150, and 300 kg hm^-2, expressed as P0, P1, P2, P3, and P4, respectively) on sweet corn yield, biomass and P accumulation and tissue distribution, P transportation and P utilization were studied using a two-year P gradient positioning field experiment. Our results showed that P application significantly increased the fresh ear yield of sweet corn, but the yield difference among different P application rates (P1-P4) was not significant from 2018 to 2019 compared with P0 treatment. P application significantly increased the biomass and P accumulation of sweet corn plants at jointing, silking and fresh eating stages, respectively. In addition, P accumulation in grain was not significant different, which accounting for 42% of plant P accumulation. With P application, the contribution rate of P assimilation to the ear P accumulation was 57.3%-93.0% after anthesis, while the fresh ear yield per P accumulation, P physiological efficiency, agronomic efficiency, recovery efficiency and partial productivity decreased with P rates. Considering the yield and utilization efficiency of phosphate fertilizer, the supply of 37.5 kg hm^-2 of phosphate fertilizer can meet the needs of high yield and efficient utilization of phosphate fertilizer in sweet corn in this experiment.     

The Effects of Replacing Dicalcium Phosphate with Busumbu Rock Phosphate on Performance and the Mechanical Properties of Bone in Growing Chicks

Three hundred, day-old broiler chicks, with an average initial weight of 41.8±1.79 g, were used in a 15-day study (10 birds per battery cage) to characterize their performance and fluorine status when dicalcium phosphate (DCP) was replaced by Busumbu rock phosphate (BRP) as the source of phosphorus in the chicks' ration. The treatments comprised a standard ration with BRP replacing 0, 25%, 50%, 75% or 100% of DCP. Replacing DCP with BRP significantly reduced the final weight of the chicks (p<0.01), feed intake (p<0.01), weight gains (p<0.01) and dry matter digestibility (p<0.05) but increased (p<0.05) the feed-to-gain ratio. True phosphorus absorption and the percentage of phosphorus in the tibia were not affected by increasing amounts of BRP in the diet. Increasing levels of BRP in the diet linearly reduced (p<0.01) the percentage bone ash, calcium, Ca:P ratio, ultimate breaking force, bending moment, stress, and modulus of elasticity. Leg stiffness, lameness, reduced feed intake, and a decline in general health were recorded in 10–40% of the chicks on 75% and 100% BRP, respectively. These results suggest that excessive ingestion of fluorine from the BRP caused the reduction in the chicks' performance.