Microsatellite variability of sulfonylurea‐resistant and susceptible populations of Schoenoplectus juncoides (Cyperaceae) in Kinki,Japan

Schoenoplectus juncoides is one of the most harmful weeds found in East Asian paddy fields. Recent emergence of biotypes that are resistant to the herbicide sulfonylurea (SU) has made weed control difficult. To examine the effect of the evolution of this herbicide resistance on genetic diversity within local populations, we investigated microsatellite variability within and among paddy field populations of S. juncoides in Kinki, Japan. In vivo assay of acetolactate synthase activity and root elongation assay in the presence of SU revealed that of 21 populations, five were sulfonylurea‐susceptible (SU‐S) and eight were completely sulfonylurea‐resistant (SU‐R). The remaining eight populations were a mixture of SU‐S and SU‐R individuals. The average gene diversity for SU‐R populations (H_S = 0.168) was lower than those for SU‐S (H_S = 0.256) and mixed (H_S = 0.209) populations, but the difference was not significant. This indicates that positive selection for SU‐R phenotype did not cause a genome‐wide reduction in genetic diversity. Genetic differentiation among S. juncoides populations was higher than that observed for most weed species studied previously. Although populations in neighbouring paddy fields showed a high level of differentiation, Bayesian clustering analyses suggested that some level of gene flow occurs among them and that the genetic exchange or colonisation between neighbouring populations could contribute to the geographical expansion of the resistant allele.     

DEM内插算法对区域坡长提取的影响分析——以陕北黄土丘陵区为例

利用陕北黄土丘陵区10m分辨率的高程数据,在Visual Studio平台下,实现双线性内插、反距离加权内插以及移动曲面拟合这三种DEM内插算法,进而对不同的内插DEM采用多流向算法实现坡长提取,最后对不同内插DEM提取的坡长进行空间结构分析、坡长精度分析、栅格坡长值的空间统计分析以及不同分辨率下(10m,25m,50m)不同内插算法坡长提取的比较分析。分析结果表明:(1)移动曲面拟合内插DEM生成的栅格坡长表面可正确表达各层级径流线信息,并具有与原始DEM以及坡度图相同的空间结构特征即表面的光滑连续特性,且其坡长提取精度最高,是适用于陕北黄土丘陵区域坡长提取的DEM内插算法;(2)空间统计分析表明,在实验区域内,不同内插算法在坡长值较小区域有显著性差异;(3)不同分辨率比较分析表明,在陕北黄土丘陵区域,不同分辨率对不同内插DEM坡长提取无显著性影响,且验证了分辨率越低坡长提取值越大的规律。     

Analysis of Phosphate Rock Dissolution Determining Factors Using Principal Component Analysis in Some Acid Indonesian Soils

Abstract

Dissolution of phosphate rock (PR) materials and its subsequent phosphorus (P) availability to plants depend upon soil characteristics, PR characteristics, type of crops, and environmental conditions. Agronomic effectiveness of the PR sources has frequently been investigated in the field or in the greenhouse. This is time consuming and not cost‐effective. Therefore, identification of the soil characteristics influencing the dissolution of PR is very important for direct application of P sources. The principal component analysis was used to summarize the characteristics of acid soils in an incubation system into a number of factors that may affect PR dissolution. Three major factors were selected in this study: 1) soil texture, 2) soil acidity, and 3) fertilization. Using the scores of the individual factors as independent variables, a stepwise regression analysis was performed to derive a PR dissolution function. The coefficient of determination (R²) reached 0.91**, and the magnitude of the different factors affect PR dissolution following the order of soil texture (54%)>soil acidity (43%)>fertilizer (3%). Fertilizer was not significant as a PR dissolution factor.     

Phosphorus Solubilization from Low-Grade Rock Phosphates in the Presence of Decomposing Soybean Leaf Litter

Abstract

The natural phenomenon of defoliation of mature soybean leaves onto the soil surface provides a large quantity of easily decomposable organic matter in the form of leaf litter. The potential of decomposing soybean leaf litter (SLL) to solubilize phosphorus (P) from two low‐grade rock phosphates, Jhabua rock phosphate (JRP) and Hirapur rock phosphate (HRP), alone or amended with pyrite, was assessed in an incubation study. Decomposing SLL solubilized P both from JRP and HRP and concurrently increased water‐soluble as well as organic P contents. Amending rock phosphates with pyrite (in a 1∶2 P to S ratio) promoted P solubilization. Approximately 71 to 92% of the total solubilized P was converted to organic P. The rate of P solubilization increased with SLL decomposition time, reaching its peak at 60 days with rock phosphates alone and at 90 days with pyrite‐blended rock phosphates. The maximum P solubilization (as a percentage of total P added) with different rock phosphates and their mixtures with pyrite followed this order: HRP (11.4%)<HRP+pyrite (16.5%)<JRP (20.2%)<JRP+pyrite (26.5%). These findings clearly suggest that the decomposing SLL has the potential to solubilize P from the otherwise insoluble low‐grade rock phosphates and can offer a natural opportunity for direct use of rock phosphates in the cropping systems that have soybean as a component crop.     

Factors Influencing the Dissolution of Phosphate Rock in a Range of High P‐Fixing Soils from Cameroon

Abstract

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo‐Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)‐sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg^?1 soil and incubated at 30°C for 85 days. Dissolution of the PRs was determined at various intervals using the ΔNaOH‐P method (the difference of the amount of P extracted by 0.5 M NaOH between the PR‐treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH‐(H₂O)<5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH‐(H₂O)>5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P=At^B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.     

Availability of Organic and Inorganic Phosphorus Fractions to Wheat in Toposequences of Calcareous Soils

Abstract

Information on the availability of different soil phosphorus (P) forms is useful for crop production. Phosphorus contents of 12 Iranian calcareous soils from upper‐, mid‐, and lower‐slope positions of two arid and two semiarid toposequences were fractionated to various organic and inorganic pools, and correlations of the P fractions with wheat responses were investigated. Among the inorganic P (IP) fractions, apatite type (Ca₁₀‐P) and dicalcium phosphate equivalents (Ca₂‐P) possessed the highest and the lowest amounts of P reserve in the soils, respectively. On average, about 20% of the total P was found in organic form (OP), of which 32% was labile (LOP), 51% was moderately labile (MLOP), and 17% was nonlabile (NLOP). The amounts of the soil P fractions were considerably influenced by the positions of the soils on the landscapes. The maximum contents of soil IP, Ca₂‐P, Fe‐P (iron‐bound P), and Ca₁₀‐P were observed in the lower‐slope positions. The amount of soil available [0.5 M sodium bicarbonate (NaHCO₃) extractable] P was significantly correlated with Ca₂P (r=0.895), Fe‐P (r=0.760), and Occl‐P (iron‐occluded P) (r=0.897). Direct correlation studies, however, showed that wheat shoot dry‐matter yield (DMY) was significantly affected by the amounts of Ca₂‐P, Fe‐P, OP, LOP, and MLOP fractions both at early (4 weeks) and late (10 weeks) stages of growth. All organic and inorganic P fractions, except Al‐P (aluminum‐bound P), Ca₈‐P (octacalcium phosphate equivalents), and NLOP, also showed significant relations to the amount and/or concentration of P in wheat tissues at 4 and 10 weeks after sowing. Among the measured soil properties, the amount of organic carbon was the most affecting factor on the size of the P fractions.     

不同初始含水量对草甸土坡面养分迁移的影响

采用室内人工降雨的方法,对不同土壤初始含水量的草甸土坡面进行养分(N、P、K)流失的研究。结果表明:土壤初始含水量越高,水分入渗速率越低,产流量越大,土壤侵蚀程度也越大。当土壤初始含水量低于15%时,土壤中的硝态氮会被淋溶到土层6cm以下,土层6cm以上的硝态氮含量极低,且淋溶的硝态氮均累积入渗到7～10cm土层中;当初始含水量在20%时,土壤中硝态氮有少量淋溶;当初始含水量在25%时,淋溶极少,仅表层1cm的土壤硝态氮有少量淋溶外,其余全部随径流流失。土壤速效钾、速效磷淋失很少。径流水样中,速效磷和速效钾浓度随降雨时间增加而逐渐减少,流失量与土壤初始含水量呈近似抛物线的关系,在初始含水量为10%～15%之间存在拐点。通过土壤初始含水量与坡面物质流失量的二次多项式关系确定出草甸土的最佳含水量范围是11.28%～14.76%,当含水量在此范围内时坡面物质流失量最少。     

模拟降雨条件下不同PAM用量及其与强化剂联用对紫色土磷素流失的影响

采用人工模拟降雨试验研究不同PAM用量及其与不同强化剂联用对紫色土坡面磷素流失的影响。结果表明:分别施加4,8,16g/m2分子量600万、水解度20%的阴离子型PAM均能显著降低坡面径流量、总磷(TP)及颗粒态磷(PP)浓度,并显著增加壤中流体积。2次降雨中,PAM应用效果均与PAM用量有关。第1次降雨以8g/m2 PAM效果最佳,相比对照,径流量减少62.28%,TP减少80.71%,PP减少95.78%;第2次降雨以16g/m2效果最佳,相比对照,径流量减少53.28%,TP减少77.52%,PP减少98.40%。相比PAM单施,分别联用石膏和石灰石后,坡面径流量增加,TP和DP浓度均显著降低。第1次降雨以石膏联用效果更佳,其中TP减少83.91%,DP减少85.34%;第2次降雨2种强化剂效果相近,TP分别减少76.10%和75.28%,DP也分别减少78.17%和79.46%。可见,施用PAM和强化剂能够显著降低磷素流失量,对农业面源污染的控制有一定作用。     

微晶化对钾长石粉钾素释放的影响

摘要: 利用微晶化设备对钾长石进行机械力活化处理,研究了不同处理时间对钾长石粉颗粒组成、 钾素释放量及生物有效性的影响。结果表明,钾长石经微晶化设备分别加工10 min、 40 min、 120 min和180 min后,微细颗粒（d10 m）组成比例分别达到51.69%、 65.44%、 85.34%和93.93%,比表面积明显增大,衍射峰强度显著减弱,同时钾素的释放量显著提高,其中微晶化处理180 min样品T3效果最好,2 mol/L HNO3和蒸馏水3次提取的钾总量分别为6118.8 mg/kg和2867.8 mg/kg; 4个处理（10 min、 40 min、 120 min和180 min）酸提钾总量分别是蒸馏水提钾总量的2.46、 1.81、 2.19和2.13倍,两种浸提剂提钾总量占钾长石全钾的0.50%~5.73%。微晶化以后钾长石粉中的绝大部分钾素仍以矿物态存在,但其生物有效性显著提高,促进了籽粒苋的生长和钾素积累。     

Effect of land use and topography on soil properties and agronomic productivity on calcareous soils of a semiarid region,Iran

In this research, the effects of land use and slope position on soil properties and its agronomic productivity were studied in a greenhouse experiment. The study also covered the effects of water stress, fertilizer treatment and their interactions. Eight soil samples were collected from four slope positions along hill slopes from two adjacent land use types of rangeland and dry farmland in a semiarid region of Iran. Soil samples were analyzed for their physical and chemical properties and yield and yield components of wheat were measured as indices of soil agronomic productivity in a replicated pot experiment. Soils of the dry farmland showed higher fertility and better quality than the soils from the adjacent degraded rangeland, especially at the upper slope positions. The results indicated that yield components of wheat were all higher for the dry farming land compared to the degraded rangeland, and at the bottom of slopes compared to the top. The effect of land use and slope position on agronomic productivity of soil was influenced by water supply. The actual impact on soil productivity of soil degradation, induced by land use and slope position, was overshadowed by the dominating effect of water stress. While both chemical fertilizer and fertilizer + manure treatments enhanced the agronomic productivity of all soils, their effects were much more pronounced on the degraded soils of the rangeland. Water stress reduced fertilizer efficiency on all the soils used in this study. Copyright © 2011 John Wiley & Sons, Ltd.