基于EMD方法的土壤入渗空间异质性及其影响因素研究

利用经典统计学方法和经验模态分解方法(EMD),分析了杨凌区、武功县和乾县临平镇一带0~40cm土层土壤物理性质(初始含水率、体积质量、有机质、颗粒组成)和入渗性能(90min累积入渗量、初始入渗率、稳定入渗率)的空间变异性,研究了EMD分量对变异的贡献率,并进一步对多尺度下土壤入渗性能与土壤物理性质进行了相关性分析。结果表明:1土壤物理特性空间序列中,除土壤体积质量变异系数为0.08、表现为弱变异外,含水率、颗粒组成及有机质均表现为中等变异,变异系数为0.11~0.35;2对于土壤入渗特性,稳定入渗率、90min累积入渗量和初始入渗率均表现为中等变异,且三者变异程度依次减弱;3EMD分解研究发现:小尺度分量对土壤入渗性能总变异的贡献率比大尺度分量高;不同的土壤物理性质对土壤入渗性能的影响随尺度变化。     

Effect of Phosphorus in Alleviation of Adverse Impacts of Salinity on Wheat Grown on Different Soils

Fertilization management is an important technique to alleviate the adverse effects of salinity stress on plants. A pot experiment was conducted to evaluate the ameliorative role of inorganic phosphorus (P) and organic P sources on wheat grown under salt stress in three soil types deficient in available P. Wheat (Triticum asetivum L. cv. Shakha 93) was grown on alluvial, sandy, and calcareous soils under salinity levels of 4, 8, and 12 dS m^?1 of saturated paste extract (EC_e) and supplied with constant rate of 30 mg P₂O₅ kg soil^?1 as superphosphate (SP), cattle manure (CM), and 1:1 mixture of SP and CM. The results revealed that plants grown on the sandy soil were more susceptible to the adverse effects of salinity compared with those planted on the alluvial one, especially at zero P. Plants grown on the calcareous soil were moderately affected. Varying soil type caused significant differences in the aboveground biomass and uptake of nitrogen (N), potassium (K), P, and zinc (Zn). It was obvious that P ameliorated wheat growth under salt stress, and this role was greater under moderate and high salinity. The increases in N, P, K, and Zn uptake appeared driven by P application were more conspicuous in the sandy and calcareous soils. Results also indicated that combined application of inorganic and organic P sources surpassed both when applied solely under all soil types and salinity levels.     

不同类型土壤的光谱特征及其有机质含量预测

 【目的】构建适合土壤有机质含量估测的高光谱参数及定量反演模型。【方法】系统分析中国中、东部地区5种不同类型土壤风干样本有机质含量与350～2 500 nm波段范围高光谱反射率之间的关系,利用特征光谱参数和BP神经网络建立土壤有机质的定量估测模型。【结果】光谱一阶导数构成的两波段光谱参数与土壤有机质含量的相关性明显优于原始光谱,尤其采用Norris平滑滤波后导数光谱效果更好。光谱参数构成形式以差值指数最好,其次为比值和归一化指数。与土壤有机质含量相关程度最高的光谱参数是由可见光区554 nm和近红外区1 398 nm两个波段的一阶导数组合而成的差值指数DI(D554,D1398),两者呈显著指数曲线关系,拟合方程为y= 184.2 ×exp[-1297×DI(D554,D1398)],决定系数为0.90。经不同类型土壤的观测资料检验,模型预测决定系数为0.84,均方根误差RMSE为3.64,相对分析误差RPD为2.98,显示估测模型具有较好的预测精度。另外,利用BP神经网络结合偏最小二乘法(PLS)对导数光谱进行分析,提取贡献率达到99.56 %的前6个主成分建立了三层BP 神经网络模型,模型决定系数为0.98,经不同类型土壤的观测资料检验,模型预测决定系数为0.96,RMSE为2.24,相对偏差RPD为4.83。比较利用DI(D554,D1398)和BP网络进行土壤有机质含量的预测结果,前者精度低于后者,但可以满足土壤有机质监测的需要。【结论】利用差值光谱指数DI(D554,D1398)和BP神经网络模型均可实现对土壤有机质的精确估测。     

重庆三峡库区加工甜橙园土壤养分状况分析

为了解重庆三峡库区加工甜橙园土壤养分含量状况,在重庆7县（区）随机选取132个果园,分析背景土壤和农化土壤pH值、有机质和有效态矿质养分含量。结果显示,分别有56.8%和60.8%的果园背景土壤和农化土壤pH值适宜甜橙生长,农化土壤酸性土比例增加;背景土壤和农化土壤有机质含量不足（<15 mg?Kg-1）的比例分别为77.3%和85.3%,碱解氮处于适宜范围的比例分别为56.8%和61.5%,有效钙过剩（高量和过量）的比例分别为79.6%和76.7%;背景土壤有效磷、钾不足(缺乏和低量)的比例分别为95.4%和72.8%,有效锌、硼不足的比例分别为54.5%和70.5%;农化土壤有效磷、钾不足的比例分别为60.8%和57.6%,有效锌、硼不足比例分别为65.9%和90.7%。背景土壤和农化土壤有效镁、铁、锰及铜不足和过量并存。总体而言,土壤养分状况中等偏差;与背景土壤相比,农化土壤pH值、有机质、有效钙、锌和硼含量下降且缺锌严重,其它养分含量则有所上升。     

草坪坪床对土壤的要求

通过对土壤理化性质及其生物组成的分析 ,对草坪坪床土壤提出了要求 ,并且提出了改良措施     

Calliandra calothyrsus as a Supplement for Milk Production in the Kenya Highlands

Two on-farm experiments and one on-station observation were conducted between July 1994 and September 1995 to study the effect of supplementation with fresh fodder of Calliandra calothyrsus on milk production from grade Friesian and Ayrshire cows in the second trimester of their lactations. The cattle were kept under zero-grazing systems on small farms in the coffee-based land use system at altitudes of 1500 to 1800 m on the slopes of Mt Kenya. These cows form a pivotal part of the farming system since they produce both milk for sale and manure for crop production. Milk production is normally in the region of 10 kg/cow per day when the animals are fed on a diet based on Napier grass and crop residues, together with 2–4 kg/day of commercial concentrate. In terms of milk production, 3 kg of fresh calliandra had the same effect on yield as 1 kg of additional dairy meal and, at normal production levels, the effects of the two supplements were strictly additive. Calliandra had a marked positive effect (about a 10% increase) on the butterfat content of the milk, a factor that was highly valued by farmers, even though institutional buyers as yet offer no premium price for milk quality. The average small farm can produce enough calliandra fodder to supplement two dairy cows and some additional small stock from relatively underutilized niches along the farm perimeter and terrace risers, without any adverse effect on current levels of crop production.     

不同耕作措施对西北绿洲灌区冬小麦农田土壤呼吸的影响

在西北绿洲灌区多年田间定位试验基础上,研究了免耕秸秆覆盖(NTS)、免耕不覆盖(NT)和传统耕作(T)3种耕作措施下冬小麦农田土壤呼吸变化特征及其对土壤温湿度的敏感性。结果表明,3种耕作措施土壤呼吸速率日变化和生育期变化呈单峰曲线。免耕秸秆覆盖处理土壤呼吸速率日峰值出现在15:00,免耕不覆盖和传统耕作处理出现在14:00。3种耕作措施土壤呼吸速率生育期峰值出现在冬小麦开花期。从冬小麦返青至成熟,免耕秸秆覆盖和传统翻耕处理土壤呼吸平均速率分别较免耕不覆盖处理高43.01%和33.33%。3种耕作措施下土壤呼吸对土壤温度的敏感性(Q₁₀)依次为NT＞NTS＞T,敏感性为1.93~3.00;3种耕作措施下土壤呼吸对土壤含水量不敏感。说明在西北绿洲灌区,不同耕作措施下冬小麦农田土壤呼吸主要受耕层土壤温度的控制。     

调亏灌溉对高寒荒漠区人工混播草地土壤环境与牧草生长的影响

针对中国高寒荒漠草原区牧草种植模式单一、产量水平低下的草业畜牧业生产现状,探究更为有效的灌水模式以提高牧草产量,以实现区域水土资源高效利用。以燕麦和箭筈豌豆混播草地为研究对象,采用大田试验对比分析了7种调亏灌溉模式（拔节期轻度亏水BW₁：65%~75%,拔节期中度亏水BW₂：55%~65%,拔节期重度亏水BW₃：45%~55%,开花期轻度亏水KW₁：65%~75%,开花期中度亏水KW₂：55%~65%,开花期重度亏水KW₃：45%~55%,以全生育期充分灌水QW₀：75%~85%为对照）对混播草地土壤水分、土壤温度和土壤养分及牧草株高、茎叶比、产量和水氮利用效率的影响。结果表明：1）平均土壤贮水量随灌水亏缺程度的提高呈降低趋势,同一亏缺度条件下,拔节期亏水与开花期亏水间无显著差异。2）水分亏缺处理的平均土壤温度显著高于充分灌水处理,且水分亏缺度一定时,拔节期亏水处理的平均土壤温度显著高于开花期亏水处理。3）收获后各处理的土壤养分含量较播种前呈降低趋势。与充分灌水相比,开花期轻度亏水可显著提高土壤速效氮含量,而中度或重度水分亏缺不利于牧草对土壤速效磷和钾的吸收。4）同一灌水模式下,燕麦株高、茎叶比和产量均显著高于箭筈豌豆。7种灌水模式的草地耗水量为386.1~502.6 mm,与处理QW₀相比,处理KW₂的灌水量减少20.6%,牧草总产量无显著差异,可获得较高的水分利用效率（31.5 kg·hm^-2·mm^-1）、灌水利用效率（81.0 kg·hm^-2·mm^-1）、氮素吸收效率（0.99 kg·kg^-1）和氮肥偏生产力（191.1 kg·kg^-1）,是高寒荒漠区燕麦与箭筈豌豆混播人工草地节水、增产和高效的水分管理模式。     

东祁连山不同土地利用方式下土壤重金属污染评价

本研究通过对东祁连山不同土地利用类型下土壤的7种重金属含量进行测定,结合青藏高原土壤元素背景值,对土壤重金属污染程度和综合潜在生态风险做出综合性评价。结果表明：7种重金属元素的均值都超过了土壤元素背景值,其中Zn和Ni平均含量较高,为196.67 mg·kg^-1和74.28 mg·kg^-1,分别是土壤背景值的3.20和3.00倍,形成了土壤重金属元素的富集现象;内梅罗综合污染指数法和潜在生态风险系数法分析显示,各类型土地平均内梅罗综合污染指数为2.84,属于中度污染程度,其中农田平均污染指数最大,为3.10,达到了重度污染水平;草地为2.71,湿地最小为2.49,均为中度污染水平。各类型土地的综合潜在生态风险系数为94.31,其中农田类风险系数最高,为101.90,草地类为92.22,湿地为73.29;各类型土壤中Zn元素变异系数最低;Cd元素变异系数最高。     

星星草对碱化土壤化学性质的影响

星星草使碱化土壤化学性质发生较明显的变化是降低了可溶性盐含量。二年生星星草对土壤含盐量的影响较大。随着星星草生长年限的增加,CO₃^2-、HCO₃^-和Na⁺含量逐年减少,Cl^-含量变化不明显,SO₄^2-和K⁺呈减少趋势,Ca²⁺和Mg²⁺则呈增加趋势。星星草对土壤含盐量、pH值、有机质、全氮、钾、钠、钙和镁含量的影响仅限于土层的一定深度。星星草土壤与碱斑土壤比较,表土层的差别较大,土层越深差别越小。从分蘖期到抽穗期(或孕穗期),0～10cm土层的全盐、pH值、CO₃^2-、HCO₃^-、Na⁺、K⁺、Ca²⁺和Mg²⁺含量逐渐升高,到完熟期逐渐降低。碱斑土壤全盐、pH值、CO₃^2-、HCO₃^-、Na⁺、K⁺含量亦表现相似规律。总之,3年生星星草土壤全盐、pH值、CO₃^2-、HCO₃^-、Na⁺、K⁺含量明显低于碱斑土壤,但Ca²⁺和Mg²⁺含量则明显高于后者。