县域耕地土壤速效磷空间格局研究

【目的】研究陕西关中地区县域耕地土壤速效磷的空间变异特征和分布格局,探讨其主要影响因子。【方法】以陕西省武功县为研究区,在0～20 cm土层,以“S”形法采集耕地土样2 219个,运用地统计学结合GIS技术,拟合最优半方差模型,进行普通Kriging插值分析。【结果】研究区土壤速效磷含量为3.10～65.80 mg/kg,平均值为21.75 mg/kg,最佳半方差模型为球状模型,且具各向异性特征,块金系数为0.360 3,具有中等强度的空间相关性。【结论】研究区土壤速效磷含量高低区域分布比较明显,总体分布状况与地貌特征基本一致。地形地貌、土壤质地、灌溉条件和施肥是影响武功县耕地土壤速效磷含量空间格局的主要因素。     

磷水平对玉米、大豆幼苗钼营养状况的影响

在不同P水平下用黄褐土盆栽玉米和大豆,生长6周进行植株和土壤钼的测定,结果表明:幼苗吸收土壤本底钼与P水平相关极显著,呈二次曲线关系。施P200ppm以上,P对幼苗吸收积累钼有明显抑制作用。P水平对钼在植株体内升降的影响因作物种类和部位而不同,大豆比玉米受影响较明显。施磷降低土壤有效钼的回收率,其下降幅度高磷>低磷,大豆>玉米,种植作物>休闲。     

冬小麦利用土壤有效钼的研究

本文就五个品种小麦对土壤钼的利用和根际土壤申P、K、Mo、Cu、Fe、Zn等对小麦利用土壤钼的影响等问题进行了研究,结果表明:小麦植株含钼量变动在0.3—0.7ppm之间,总趋势是与日递减;不同植株部位Mo平均浓度,就5个品种平均位而言,以旗叶最高,麦秸最低。小麦积累Mo的速率生育期中差异很大,泗阳、宁麦、7959都有两个吸Mo速率高峰,同时出现在4月13日附近和5月12日附近,青农和百农只在5月3日出现了一个高峰。小麦60%的Mo是在最后半个月积累的,全生育期中对土壤有效Mo的最高利用率也仅3%。根际土壤中P能促进小麦对Mo的积累,相关系数r=0.7～.80(n=8),达显著或极显著水平,而根际土壤中K、Cu、Fe与小麦Mo积累呈不同显著程度的负相关,各相关程度因品种而异。体内N、P、K、Zn和Cu与Mo之间都表现极显著的正相关,r=0.571～0.822(n=39),并与Mo浓度始终保持一定比例,大量元素与Mo浓度比约为10,000,Zn约为120,Cu约为20。     

长期地膜覆盖与施肥条件下土壤中磷素的变化

采用对比法对沈阳农业大学长期(1987～2005)地膜覆盖定位试验地棕壤中磷素的变化情况进行了研究。结果表明,经过19年的长期耕作,施有机肥或磷肥均能显著增加土壤中全磷、有机磷和速效磷的含量,但都不如有机无机肥配施;覆膜后除N4P2处理外,其余处理土壤全磷含量均大于裸地,覆膜后有机磷含量与裸地相比变化不大。地膜覆盖明显减少了速效磷的含量,增加了磷的移出量。同时表明增施有机肥是恢复和提高覆膜后土壤磷素肥力的较好措施。     

A flexible approach to managing variability in grain yield and nitrate leaching at within-field to farm scales

We up-scaled the APSIM simulation model of crop growth, water and nitrogen dynamics to interpret and respond to spatial and temporal variations in soil, season and crop performance and improve yield and decrease nitrate leaching. Grain yields, drainage below the maximum root depth and nitrate leaching are strongly governed by interaction of plant available soil water storage capacity (PAWC), seasonal rainfall and nitrogen supply in the water-limited Mediterranean-type environment of Western Australia (WA). APSIM simulates the interaction of these key system parameters and the robustness of its simulations has been rigorously tested with the results of several field experiments covering a range of soil types and seasonal conditions in WA. We used yield maps, soil and weather data for farms at two locations in WA to determine spatial and temporal patterns of grain yield, drainage below the maximum root depth and nitrate leaching under a range of weather, soil and nitrogen management scenarios. On one farm, we up-scaled APSIM simulations across the whole farm using local weather and fertiliser use data and the average PAWC values of soil type polygons. On a 70 ha field on another farm, we used a linear regression of apparent soil electrical conductivity (EC_a) measured by EM38 against PAWC to transform an EC_a map of the field into a high resolution (5 m grid) PAWC map. We then used regressions of simulated yields, drainage below the maximum root depth and nitrate leaching on PAWC to upscale the APSIM simulations for a range of weather and fertiliser management scenarios. This continuous mapping approach overcame the weakness of the soil polygons approach, which assumed uniformity in soil properties and processes within soil type polygons. It identified areas at greatest financial and environmental risks across the field, which required focused management and simulated their response to management interventions. Splitting nitrogen applications increased simulated wheat yields at all sites across the field and decreased nitrate leaching particularly where the water storage capacity of the soil was small. Low water storage capacity resulted in both low wheat yields and large leaching loss. Another management option to decrease leaching may be to grow perennial vegetation that uses more water and loses less by drainage.Paper from the 5th European Conference on Precision Agriculture (5ECPA), Uppsala, Sweden, 2005     

Management Zones Classified With Respect to Drought and Waterlogging

Within-field variations in potential grain yield may be due to variations in plant available soil water. Different water holding capacities affect yield differently in different years depending on weather. By estimating plant-water availability in different weathers, scenarios could be created of how yield potential and thereby fertilizer demand may vary within fields. To test this, measured cereal grain yields from a dry, a wet and an intermediate year were compared with different soil moisture related variables in a Swedish arable field consisting of clayey and sandy areas. Soil water budget calculations based on weather data and maximum plant available water (PAW), estimated from soil type and rooting data, were used to assess drought. A reasonable correlation between estimated and measured soil moisture was achieved. In the dry year, drought days explained differences in yield between the clayey and the sandy soil, but yield was better explained directly by maximum PAW, elevation, clay content and soil electrical conductivity (SEC). Yield correlated significantly with SEC and elevation within the sandy soil in the dry year and within the clayey soil in the wet year, probably due to water and nitrogen limitation respectively. Dense SEC, elevation and yield data were therefore used to divide the field into management zones representing different risk levels for drought and waterlogging. These could be used as a decision support tool for site-specific N fertilization, since both drought and waterlogging affect N fertilization demand.     

香蕉地土壤pH的空间变异及其对土壤速效钾的影响

以香蕉种植区127hm2香蕉地为研究对象,网格法(100m×100m)采集表层(0~30cm)土样170个,采用传统统计和地统计学相结合的方法,研究土壤pH及速效钾的空间变异特征。结果表明:土壤pH和速效钾有明显的空间变异结构;pH变异函数符合线性模型,速效钾符合指数模型,pH和速效钾具有中等的空间相关性;土壤速效钾与pH呈极显著正相关,表明研究区域内土壤钾素的有效性受土壤pH的明显影响,土壤pH的升高或降低是导致土壤速效钾变化的主要原因之一。通过研究土壤速效钾的空间变异性,获取香蕉地土壤速效钾、pH的连续分布图,为土壤钾养分分区管理及科学施肥提供依据。     

南方森林土壤溶解有机碳与土壤因子的关系

采用TOC-5000A总有机碳仪测定了福建主要森林类型土壤溶解有机碳(DOC)的含量，分析了土壤溶解有机碳与土壤因子的关系。结果表明：南方酸性森林土壤中，DOC与有机碳总量、全氮、全磷、碱解氮、有效磷和速效钾等养分因子之间呈极显著或显著的正相关关系，因而可以作为评价土壤肥力性状的生物学指标。土壤DOC与土壤中有机络合态铁、有机络合态铝和活性轻基铝之间呈权显著或显著的正相关。土壤中有机碳是影响土壤中铝和铁的溶出及迁移的一个重要因子。土壤DOC与pH值之间在一定的范围内呈权显著的负相关关系，因而土壤中铝的吸附、保持及溶解铝的排出受到溶液中DOC的强烈控制。土壤DOC与交换性铝之间无显著相关性。表2参14     

京郊潮土有效养分周年变化规律的研究

在北京北郊高、中、低三种肥力水平的潮土上,研究了土壤有效氮、磷、钾的周年变化规律.结果表明;土壤有效氮的含量为冬、春季低于作物生长时期的夏、秋季,而有效磷、钾含量则是夏、秋季低于冬、春季.影响这种变化的因素,主要是气温、降水、作物吸收和土壤微生物的活性等.     

双层量子点阵列浮栅结构纳米存储器

设计了一种新型的存储器结构单元——锗／硅双层量子点阵列浮栅结构纳米存储器．对存储器样品的C—V测量结果显示了这种结构的P沟道器件有着更加优异的存储性能．数值模拟表明了该器件的编程速度在微秒量级，而保留时间长达10年（约10^8S）．这种新型的存储器结构单元有效地解决了目前硅基纳米存储器存在的工作电压和长久存储之间的矛盾，为硅基纳米存储器的实用化拓宽了道路．