Phosphorus Response and Fertilizer Recommendations for Wheat Grown on Nitisols in the Central Ethiopian Highlands

The provision of farmers with proper and balanced fertilizer recommendations is becoming increasingly important, for reasons of crop productivity, food security, and sustainability. Phosphorus (P) response trials with wheat were conducted on Nitisols at 14 sites in the central Ethiopian highlands during the 2010 and 2011 cropping seasons. The treatments, comprising six levels of P fertilizer (0, 10, 20, 30, 40, and 50 kg P ha^?1), were arranged in a randomized complete block design with three replicates. Based on a yield difference between the control and the P treatments, 90% of sites responded to P fertilizer. Application of P fertilizer increased wheat grain yield, up to 30% more than the control. Extractable soil P concentrations (Bray 2, 0–15 cm deep) 3 weeks after planting significantly responded to P fertilizer rate. The critical P concentration (for 90% relative yield) was 13.5 mg kg^?1. Most sites tested had Bray 2 P values <10 mg kg^?1. In the absence of a soil test, a recommendation of 40 kg P ha^?1, resulting in the best response overall, could be made for the first year of application. We also recommend that to prevent a potential loss of wheat yield, a maintenance application of at least 5–12 kg P ha^?1 be applied every year, irrespective of the calculated recommended rate, in order to replace P exported from the field in produce. Further field trials are required to determine interactions between P response and the effects of climate, soil properties, and other management practices.     

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.     

不同氮磷配比对旱作土壤养分和油葵产量的影响

采用调查分析、田间试验等方法,研究了旱作土壤条件下油用向日葵氮磷肥的吸肥特性和对氮磷肥的吸收规律。结果表明:不同厚度(0～20cm)和(20～40cm)的土壤对养分的吸收呈现动态的变化特点,施氮270.0kg/hm2时吸收氮素分别为47.5和35.7mg/kg,相差24.8%;油葵产量为2 604.0kg/hm2,施磷100.05kg/hm2时吸收磷素分别为28.4和21.5mg/kg,相差24.2%,油葵产量为3 199.5kg/hm2。     

Effect of zinc levels on phosphorous and zinc content in sand‐cultured soybeans

Soybeans (Glvcine max L.) cv. “Clark”; were grown in the greenhouse in sand‐filled plastic pots sub‐irrigated with Hoagland No. 1 solution to determine the possible inhibitory effects of Zn on the uptake of P. Zinc rates used were 0.05 (control), 0.25, 0.5 and 2.5 ppm. Yields equalled the control at Zn levels of 0.25 and 0.5 ppm, but plants grown in solutions containing 2.5 ppm Zn were stunted severely. Foliar Zn and P levels differed very little among Zn treatments. Zinc levels were highest and P levels were lowest, however, in the roots and stems of soybeans grown in solutions of 2.5 ppm Zn. Zinc and P uptake was significantly inhibited in the leaves, stems and roots of plants grown at the highest Zn rate. The recycling of wastes containing high Zn content could adversely affect plant growth by a suspected antagonism with P.     

大豆黄酮对伊莎鸡卵泡发育及其P450arom基因表达的影响

实验探讨了大豆黄酮(DAI)对伊莎鸡卵泡发育及其芳香化酶(P450arom)mRNA表达的影响。实验选取16只产蛋后期伊莎鸡,等分为对照组和DAI处理组。对照组饲喂基础日粮,实验组在基础日粮中添加10 mg/kgDAI。实验持续7周后,分离排卵前卵泡(F1、F2、F3……)的颗粒层及小黄卵泡和大白卵泡,通过RT-PCR法检测P450arom mRNA表达的相对丰度。结果表明:DAI明显提高了伊莎鸡小黄卵泡和大白卵泡的数量,P450arommRNA在伊莎鸡不同发育阶段卵泡中的表达存在差异,部分卵泡P450arom mRNA表达的相对丰度显著增加。因此,在产蛋后期伊莎鸡基础日粮中添加DAI可增加不同发育阶段卵泡的数目,上调部分卵泡中与发育相关的基因表达以促进卵泡发育。     

华北落叶松和白杆幼苗脯氨酸及淀粉含量对水分和光照变化的响应

以2年生华北落叶松和白杆幼苗为研究对象，通过人工控制条件下的幼苗栽培试验，测定不同光照、水分条件下脯氨酸含量、淀粉含量的变化，综合比较分析了华北落叶松和白析苗期生长对光照和水分变化的生理响应。研究结果表明：随着土壤水分的减少，华北落叶松和白不工幼苗脯氨酸含量增高，淀粉含量下降，且华北落叶松的变化都高于白杆，华北落叶松幼苗比白析幼苗对土壤水分胁迫的响应能力更强；随着光照的增强，也有相同的表现。光照和水分条件的变化对华北落叶松和白析幼苗脯氨酸和淀粉含量的影响具有叠加作用，2个树种对水分胁迫和强光照的响应机制一致，但树种间响应强度不同，华北落叶松的响应能力更强，华北落叶松具有比白术千更大的抗干旱胁迫的生理基础。     

不同氮磷钾配比对仙客来生长的影响

对仙客来无土栽培营养液中N、P、K元素采用三因素二次D-饱和最优设计,探讨不同浓度氮磷钾对仙客来生长发育的影响,对仙客来的根长、根体积、球茎直径、花朵数、花瓣长、可溶性糖含量、MDA含量、蛋白质含量、叶绿素含量进行分析。结果表明:经方差分析和主成分分析得出,无土栽培仙客来氮、磷、钾最优组合方案为:86.6~263.4、60~100和250~400 mg/L,即氮:磷:钾为3∶1∶6.5。     

Forest soil chemical changes following fire

Abstract

Prescribed fire to remove residue in a pine plantation on a sandy soil resulted in increases in pH, P, K and Ca in the top 20 cm of soil during the first 15 months following treatment.     

Phosphorous accumulation and distribution of two ecotypes of Pilea sinofasciata grown in phosphorous-enriched soils

Water eutrophication and poultry manure require an efficacious remediation technology to decrease phosphorous (P) concentration. In this study, the P phytoremediation potential of a mining (ME) and nonmining ecotype (NME) of Pilea sinofasciata were analyzed by pot experiments employing different concentrations of P treatments (CK, P100, P200, P400, P800 and P1600) in tested soil. Growth, P accumulation and P-relevant enzyme activities of P. sinofasciata in ME and NME were assessed after 10 weeks’ plantation. The results showed that there was no significant difference between the shoot biomass of the ME and NME. Higher P concentration and accumulation were observed in the ME than NME for all treatments. Stem P concentration of the ME were 117%, 189%, 152%, 153%, 140% and 139% higher than the NME, and leaf P concentration were 122%, 146%, 138%, 144%, 137% and 113%. Maximum P uptake and phytoextraction was observed at P400 for the ME of P. sinofasciata. Elevated activities of acid phosphatase and phytase in roots were examined in P-enriched soil, and the ME presented higher activities compared with the NME. The results in this paper provide a theoretical basis for the use of ME of P. sinofasciata for phosphorus accumulators and suggest that ME of P. sinofasciata is a promising species for the excess P phytoextraction of P-enriched soils.     

Root Exudates of Rice Cultivars Affect Rhizospheric Phosphorus Dynamics in Soils with Different Phosphorus Statuses

Exudation of organic acids by the roots of three rice cultivars grown in three soils of different phosphorus (P) statuses, and their impacts on the rhizospheric P dynamics and P uptake by the rice plants, were investigated. Quantum root exudates from all the rice cultivars were significantly greater at 21 days after transplantation than at panicle initiation or flowering stages. Malic acid was the most predominant organic acid present in the rice root exudates (10.3 to 89.5 μmol plant^?1 d^?1), followed by tartaric, citric, and acetic acids. Greater exudation of organic acids from rice grown in P-deficient soil by all the rice cultivars suggested response of rice plant to P stress. Results indicate that the release of organic acids in the root exudates of rice plants can extract P from strongly adsorbed soil P fraction, thereby increasing native soil P utilization efficiency and ensuring adequate P nutrition for the growing rice plants.