Distribution and Dynamics of Phosphorus in an Agricultural Watershed with a Long-Term History of Poultry Waste Application

The objective of this research is to investigate the effects of long-term broiler litter application on soil phosphorus (P) and water quality and examine the spatial variations of soil P at a private poultry farm in Mississippi. Results indicated that the littered soil had 86 times more Mehlich III–extractable P in the surface horizon compared to the nonlittered soil. When compared to the runoff from nonlittered soil, mean soluble phosphate (PO₄)-P concentrations in the littered soil's runoff were 85 times greater throughout the study. Mass loss of P from the littered field was significantly greater than from the nonlittered field, and it decreased with each sequential runoff event. There were no linear relationships between the spatial variations of litter application rates and the P spatial variability in the littered soil; however, the variations in soil P levels could be a result of the cumulative effects of more than 20 years of litter application.     

Effects of Carbofuran on Availability of Macronutrients and Growth of Tomato Plants in Natural Soils and Soils Amended with Inorganic Fertilizers and Vermicompost

The effects of lower field rate (LFR), field rate (FR), and higher field rate (HFR) applications of carbofuran on ammonium (NH₄)-nitrogen (N), nitrate (NO₃)-N, available phosphorus (P), and available potassium (K) contents in natural soils and those amended with inorganic fertilizers and vermicompost on the growth of tomato plants were studied. The NH₄-N, NO₃-N, available P, and available K contents increased up to FR but the most significant increase in was observed at LFR of carbofuran application. At HFR there was a significant reduction in nutrient availability. With passage of time all these parameters increase up to 30 days; thereafter, a decrease was observed up to the end of the experiment in both unamended and amended soils. The greater plant growth was observed at LFR of carbofuran application and at HFR the plants exhibited phytotoxicity in the form of marginal leaf scorching in both systems. The morphological growth parameters of tomato plants were positively correlated with nutrients availability.     

Correlation of Soil pH and Mehlich‐3 Phosphorus with Postflood Rice Phosphorus Concentrations in Arkansas

Abstract

Plant‐available phosphorus (P) measured by routine soil‐test methods is poorly correlated with rice grain yield in Arkansas. Our objective was to determine whether soil water pH (pH_w) and Mehlich‐3 P were correlated with growth and yield of rice grown on silt loam soils. Data from 35 field studies were used to correlate Mehlich‐3 P and pH_w with relative yield, dry matter accumulation, and P concentration at the midtillering stage. Significant linear or nonlinear relationships between pH_w or Mehlich‐3 P with rice growth parameters were delineated but explained less than 27% of the variability in dry matter and P concentrations at the midtillering stage and grain yield at maturity. Mehlich‐3 P and pH_w together explained 61% of the variability in midtillering P concentrations. Midtillering whole‐plant P concentrations were positively related to relative grain yield and dry matter production and will be used to identify soils with limited P availability for rice in Arkansas.     

Sulfur content of plant material: A comparison of methods of oxidation prior to determination

Abstract

Procedures for S determination involving digestion of plant material with HNO₃/HClO₄ mixtures gave lower values than those using oxygen flask combustion. Tests on a range of S compounds showed that the HNO₃/HClO₄ procedure underestimated S present in methionine, cysteine and glutathione but S in sulfate and the glucosinolate, sinigrin, was not underestimated.

Low recoveries using HNO₃/HClO₄ digestion procedures can be due both to incomplete oxidation of certain compounds and to gaseous losses during the vigorous boiling stage of digestion.     

Relationship between Olsen P and Ammonium Lactate–Extractable P in Portuguese Acid Soils

The soil phosphorus (P) test in Portugal is based on extraction with ammonium lactate (AL) at acidic pH. Because this test is rarely used in other countries, it is desirable to see whether the AL-P values correlate with the more commonly used P tests. In this work, we compared AL-P with bicarbonate-extractable P (Olsen's method) for a group of 48 samples from Portuguese acidic soils differing widely in P status. Despite their contrasting composition, both reagents extracted phosphate from the same sources, albeit in different proportions. Both Olsen P and AL-P were strongly correlated with resin-extractable and dilute electrolyte-desorbable P, which are respectively related to the soil contents in phytoavailable P and P that can be released to runoff or drainage water. Olsen P and AL-P were strongly correlated (R² = 0.870), the correlation became stronger when three overfertilized soils were excluded (Olsen P = 2.35 + 0.45 AL-P; R² = 0.908; P ≤ 0.001, n = 45). No correlation was observed for a group of soils recently fertilized with Gafsa phosphate probably because the acidic AL reagent dissolved residual calcium phosphate, thus overestimating the soil content in desorbable P. On the basis of the present results and the AL-P-based fertility classes used for fertilizer recommendation purposes, Olsen P–based fertility classes were tentatively proposed for Portuguese acidic soils.     

Effect of Cropping on Changes in Phosphorus Fractions of Soils from Arable and Other Forest Land Use: A Greenhouse Bioassay

Abstract

Laboratory and greenhouse studies were conducted on six soils from natural reserves, seven plantation soils, and two arable soils from the Omo biosphere reserves in southwestern Nigeria to assess the phosphorus (P) fractions and the extent to which the soils could support five consecutive cycles of maize (Zea mays L.) harvest. The organic‐P fractions constitutes about 50% of the total P, and the inorganic‐P fractions in the order of abundance was iron (Fe) P>occluded P>aluminum (Al)‐P>calcium (Ca) P. The residual P constituted about 20% of the total P. There were significant reductions in the inorganic‐P fractions after five consecutive maize harvests; this was however, more pronounced in the available P (Bray 1). About 62% reduction in Bray 1 P was recorded after maize harvests. The reductions in the P forms after five cycles of maize harvest was Bray 1 P>Ca P>residual P>Al P>total P>Fe P>organic P>occluded P>reductant P. The capacity of the soils to support maize growth without fertilization varied widely in each of the maize cycle. Soil from natural reserves produced a significantly higher maize yield compared to most plantation soils. The arable soils investigated were depleted of their fertility after the third crop harvest.     

鹿角托盘总蛋白的提取工艺研究

[目的]优化鹿角托盘总蛋白提取工艺。[方法]以总蛋白得率为评价指标,采用单因素试验和正交试验设计优选最佳提取工艺。[结果]最佳提取工艺为：用含0.3mol/LNaCl,20mmol/LNa2HPO4缓冲液（pH值为9）提取,料液比为1：15,提取时间为24h,提取3次。在此工艺条件下,总蛋白得率达10%以上。[结论]试验优选出的工艺稳定、合理、可行。     

Buckwheat (Fagopyrum esculentum Moench) Potential to Contribute Solubilized Soil Phosphorus to Subsequent Crops

Reports supporting folklore beliefs that buckwheat (BW) can significantly contribute solubilized phosphorus (P) from sparingly soluble soil P to subsequent crops remain anecdotal. To quantify P solubilized by BW from five inorganic and three organic pools in a Fargo silty clay, spring wheat (Triticum aestivum L.) (WHT) was grown as a reference crop to compare P mineralized and P uptake in a complete randomized design. Following fractionation and analysis, P changes between pools indicated solubilization from recalcitrant to less recalcitrant P pools. Calcium-bound P contributed the most P (72% of inorganic pool) to the available fraction, and P uptake by BW (40 kg ha^?1) was significantly greater than wheat (16 kg ha^?1) from the inorganic pools, whereas WHT uptake was significantly greater (P < 0.05) from the organic pool. Following harvest, more P was found in available P pools after BW compared to WHT, suggesting potential solubilization of P to subsequent crops compared with WHT.     

Short and long‐term distribution with depth of soil organic carbon and nutrients under traditional and conservation tillage in a Mediterranean environment (southwest Spain)

The impacts of tillage and cropping sequences on soil organic matter and nutrients have been frequently reported to affect the uppermost soil layers, but there is little published information concerning effects at greater depth. This article reports results on the distribution of soil organic carbon (SOC), active carbon (AC), N, Olsen‐P and extractable K within 100 cm in short (4 yr) and long (16 yr) term experiments under different tillage systems. Short (TT₄) and long (TT₁₆) traditional tillage are compared with conservation tillage, reduced (RT₁₆) and non‐tillage (NT₄). The results show more accumulation of SOC in the near‐surface under RT₁₆ and NT₄ in both experiments compared with traditional tillage. Moreover, greater C content occurs to 40 cm depth in the long‐term experiment. The results demonstrate the importance of time on C accumulation, not only in near‐surface layers but also at greater depths. Active C is an indicator of the increase in soil quality in the long‐term experiment. This trend is only apparent for the first 10 cm in the short‐term experiment. Patterns in N, Olsen‐P and extractable K are similar to that of SOC. However, only extractable K is significantly greater in soil under conservation tillage (RT₁₆ and NT₄) after short and long periods. Potassium availability is a good indicator of the changes caused by tillage. Our results indicate that studies of soils at depth could be very useful in long‐term experiments to demonstrate the effect of conservation tillage on C and nutrient distribution.     

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。