The Humus Content and Soil Biological Properties as a Function of Organic and Mineral Fertilization

There is a growing recognition for the need to develop sensitive indicators of soil quality that reflect the effects of land management on soil and assist land users in promoting sustainability of agro-ecosystems. Three soil enzymes (dehydrogenase, phosphatase and invertase) microbial biomass as biological variables and soil organic matter content (SOM) were investigated relative to fertilization and soil fertility (estimated by crop yield) at a long-term fertilization trial (Keszthely, Hungary). 0-34.7-69.4-104.1t farmyard manure (FYM) ha m 1 5 yr m 1 and the corresponding amount of mineral fertilizers (NPK) were applied in two different crop rotation systems. There were four straw and/or stalk incorporating treatments in the second crop rotation 'B'. Enzyme activities, microbial biomass and the amount of SOM were generally higher in the fertilized soils than in the unfertilized soils. The type of amendments (mineral, FYM or mixed) had significant effects only on the amount of SOM. The correlations among the biological variables and the crop yield were generally low (r < 0.250. The differences in field management resulted only in the invertase activity.     

Level and Timing of Nitrogen Fertilizer Application to Early and Semi-early Potatoes (Solanum tuberosum L.) Grown with Irrigation on Light Soils in Norway

Trials were performed with early and semi-early potatoes to test the effects of nitrogen (N) fertilizer level (0-160 kg N ha^-1) and timing (all at planting versus half then and half either soon after emergence or 3 weeks later). All seven trials with earlies were irrigated as required, whilst different irrigation regimes (moderate versus intensive) were compared in two trials with semi-earlies. No benefit was derived from splitting the N application. Haulm growth and N uptake increased in all cases almost linearly up to the highest N level, but tuber yield did not respond in the same way. The optimum N level was 80 kg N ha^-1 for a yield of 15 Mg ha^-1, rising to 120 kg N ha^-1 for a yield of 40 Mg ha^-1. Tuber quality was lowered by the use of excess N fertilizer, particularly in the case of earlies. The quantity of mineralised N present in the soil after harvest rose sharply with above optimum fertilizer use, and the amount of N present in crop residues also increased. The likely leaching after early potatoes was estimated to be up to 80 kg N ha^-1. The proportion of fertilizer N which was not accounted for in either tuber yield, crop residues or mineral N in soil was 26% in earlies and 38% in semi-earlies.     

Influence of Extreme Management on Decomposable Soil Organic Matter Pool

Basing on two long-term model experiments (microplots as well as greenhouse pot experiment) the influence of extreme management on a very easily decomposable pool of soil organic matter (SOM) was measured. The carbon content (C hwe ) of a hot water extractable pool of SOM was used as an indicator for the decomposable C pool. This parameter reflects both the dynamics of the amount of decomposable organic C pool and the different transformation conditions in case of the pot experiment (outside versus inside the greenhouse). Depending on soil type and both the total and decomposable organic matter level at the starting point of the experiments we can observe differences in the decreasing speed of the decomposable C pool: in the soils having a high level of SOM at starting point C hwe pool decreases more rapidly compared to the soils unfertilized or in case of the only P and K treatment of the Static Fertilization Experiment at the beginning of the pot experiment. At least we can observe a difference in decreasing intensity of this C hwe pool when comparing different soil types.     

Relations Between Net Nitrogen Mineralization and Soil Characteristics Within an Arable Field

Within-field variations in plant-available soil nitrogen (N) are likely to be affected by differences in soil characteristics. To study this, a 3- year field investigation was conducted during 1998-2000 on a 15 ha arable field in Sweden with considerable within-field soil texture variability. In 34 plots soil N uptake by crops, net nitrogen mineralization (Nm) during the growing season and soil mineral N in spring and shortly after harvest were determined. Beside these parameters, topography, soil organic matter content (SOM), clay content, pH(H 2 O) and grain yield were recorded. The variations in Nm were considerably large both within the field and between years. The within-field variation in Nm could partly be explained by the variation in SOM and clay content (adjusted coefficient of determination = 0.23, P <0.001). The pattern in Nm differed between years, partly because of seasonal variations in soil moisture. For these reasons, the pattern of Nm is difficult to predict without seasonal adjustments.     

晋南盆地夏播玉米种植密度对产量及其相关性状变异系数的影响

为确定‘郑单958’玉米品种在晋南盆地夏播的合理种植密度,充分发挥该品种的增产效能,在山西临汾采用随机区组设计方法研究了种植密度对产量及其相关性状变异系数的影响。结果表明:在降雨正常年份,籽粒产量、千粒重、穗长、穗粗和单穗重在不同种植密度间存在差异,而出粒率、穗行数和收获指数不存在差异;种植密度对相关性状的变异系数影响序列为单穗重>籽粒产量>千粒重>穗长>穗粗>穗行数>出粒率>收获指数;穗长、穗粗和穗轴重对单穗重(籽粒)的贡献大小为:穗长>穗粗>穗轴重。晋南盆地夏播玉米增加种植密度可显著提高籽粒产量,其籽粒产量是随干物质积累的增加而协同提高,对收获指数性状影响较小。该项研究为晋南盆地夏播玉米增加种植密度提供了理论和技术支撑。     

玉米种质苗期耐盐性的评价

以苗情、株高及干重变化率为分级指标,用浓度为250 mmol/L的NaCl溶液对96份玉米自交系进行苗期耐盐性鉴定。结果表明：A069、F564/711、oh45/O₂和黑玉米等8个自交系为高耐,黄早四、Mo17和ZP291自交系敏感或高敏感;以株高变化率、干重变化率和苗情的分级结果较为一致,其中任何两个变量之间的相关性均达到极显著水平;高耐、耐盐、中耐、敏感和高敏感类型所占比率分别为20.8%、51.0%、22.9%、4.2%和1.0%。     

应用物元分析法评价矿区周边土壤重金属污染的变化

为分析煤矿开采对土壤重金属污染水平的影响,尝试利用物元分析和主成分分析(PCA)方法对宿州市矿区周边土壤重金属污染水平进行评价。结果表明:(1)煤矿开采、堆放对土壤重金属污染具有重要影响,与非矿区背景值相比,Cr含量达到非矿区土壤背景值的2~4.17倍,Cd含量达到非矿区土壤背景值的1~3.05倍,Pb和Cu含量达到非矿区土壤背景值的2倍左右,As的含量略高于非矿区土壤背景值。(2)综合关联度结果显示,土壤重金属污染在100 m处未达到轻度污染的标准要求,但具备向轻度污染转化的条件;200 m和400 m处分别达到轻度污染和清洁等级要求,但隶属该等级的程度不强,且随着距离增大土壤重金属含量和污染程度均在下降。(3)物元模型能够揭示每个土壤重金属元素的分异信息和综合评价的中间信息,适用于土壤重金属污染水平评价。     

稻茬田肥力水平与施氮量对小麦籽粒产量和物质生产的影响

为给江苏淮北麦区不同肥力土壤上小麦高产施氮提供理论依据,以该麦区主推中筋小麦淮麦19和强筋小麦烟农19为材料,研究了高、中、低肥力稻茬田上施氮量对小麦籽粒产量和物质生产的影响。结果表明,产量与施氮量在高、中土壤肥力条件下呈二次曲线关系,在低肥力条件下呈线性关系;高、中肥力条件下获得最高产量所需施氮量淮麦19分别为246.7和286.1 kg·hm-2,烟农19分别为247.9和292.6 kg·hm-2;不同土壤肥力水平的高产处理在各个生育时期均有相应较高的群体质量性状。各土壤肥力条件下的不同施氮量处理,由于小麦物质生产多方面因素的综合作用,均出现了各自相对的最高产量,而最高产量随土壤肥力提高而显著上升,相反取得最高产量所需的施氮量却依次相应降低。因此,小麦生产中要因土壤肥力水平的高低来制定不同的目标产量以及相对应的精确施氮量。     

旱地生态系统生态流与价值流耦合途径的研究

在界定了旱地生态系统基础上,阐述了旱地生态系统的物质流、能量流、信息流和价值流的基本特征,分析了制约旱地生态系统生态流与价值流耦合的主要因素,提出了实现旱地生态系统生态流与价值流耦合的基本途径。     

两个不同适应性冬小麦品种的竞争能力

采用生态学中的de Wit替代系列法研究了当前山东省高产广适性冬小麦品种鲁麦21和仅适应局部地区种植的冬小麦品种烟农15在混播条件下的竞争结局,并对其生长特性、资源分配模式及相关性状的差异进行了比较研究. 在混播条件下鲁麦21较烟农15具有明显的竞争优势, 具有更强的占有和利用共同资源的能力. 分蘖数、单位面积穗数、穗