东北农牧交错带小尾寒羊集群放牧系统中钙、磷元素营养状况分析

对我国东北农牧交错带内小尾寒羊集群放牧生态系统中5、7、9月钙、磷元素的营养状况进行了分析。结果表明:牧地土壤中钙、磷元素的总平均含量分别为1.46%、178.88μg/g;小尾寒羊2种主食牧草中钙、磷元素的总平均含量分别为0.39%、256.26μg/g;小尾寒羊羊毛中钙元素的总平均含量为2111.45μg/g;小尾寒羊羊血中钙、磷元素的总平均含量分别为69.65μg/g、10.21μg/g;小尾寒羊羊骨中钙、磷元素的总平均含量分别为4.44%、2.45%。据此认为,在该交错带集群放牧的小尾寒羊不会发生钙缺乏症或中毒病,但可能发生磷缺乏症。     

不同灌排模式稻田排水中氮磷流失规律

为了研究不同灌排模式稻田排水中氯磷流失规律,以集成合理的节水灌溉与控制排水技术,在江苏高邮开展田间试验.试验区排水斗沟出口处设水位调控闸门,在水稻不同生育阶段对排水沟水位及田间水分进行控制,形成新型的控制灌排模式.与常规灌排模式进行对比,两年田间试验成果表明,控制灌排模式较常规灌排模式节水16.7%,增产7.1%,排水总量减少54%,水稻全生育期稻田排水中NH4+;-N、NO3-N与TP流失总量分别减少38.07%、82.29%和52.15%,节水减排和降污效果显著.采用控制灌排模式,通过实施灌水调控和排水管理.控制了氮磷流失关键时期的排水量.高效利用了水分和养分,取得了节水高产、减排控污的效果.     

Short Root Densities and Surface Phosphatase Activities of Ectomycorrhizal Morphotypes in a Slash Pine Plantation

Abstract

Mineralization is the dominant process controlling soil-solution P in the Spodosols of the southeastern United States. Pine trees growing in these soils are typically colonized by ectomycorrhizal (EM) fungi that are known to produce phosphatases. Little, however, is known of the dynamics of EM short roots or phosphatase activity in tree plantations. To address this question, short root densities, EM morphotypes, and associated surface acid phosphomonoesterase in a 12-year-old Pinus elliottii plantation in northern Florida were evaluated. The density of total (living and dead) short roots changed little from February through June, with a mean of 7.6 cm³ soil. The majority of the short roots, however, were inactive or dead with only 14 to 38% appearing viable upon visual inspection. The majority of the viable short roots were mycorrhizal. The most abundant morphotypes were formed by Cenococcum and Thelephora but these had low phosphatase activity. In contrast, less frequently observed morphotypes had substantially higher rates of enzyme production and these may play an important role in sustainable P nutrition of plantation trees.     

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.