塿土不同层次钾运移研究

以陕西杨凌西北农业大学农作一站的土娄土为研究对象 ,通过稳定流土柱运移试验测定不同层次钾运移穿透曲线 ;应用对流、扩散模型对测试穿透曲线进行拟合 ,反求其运移参数D、R ,结果表明 ,钾在土娄土不同层次的运移均受到强烈的阻滞作用。土娄土的阻滞因子与土娄土各层次的粘粒含量成正相关 ,线性关系极显著 ;土娄土的扩散、弥散系数与平均孔隙水流速成极显著的线性关系 ,符合一般规律。

塿土和黑土不同层次钾运移研究

以采自陕西省杨凌区西北农林科技大学农作一站的土娄土和黑龙江省农业科学院土壤肥料研究所试验田的黑土为研究对象,通过饱和稳定流土柱运移实验,测定不同层次土壤钾运移穿透曲线;应用对流、扩散模型,对测试穿透曲线进行拟合,反求其运移参数D、R,结果表明:钾在土娄土和黑土不同层次的运移均受到强烈的阻滞作用。土娄土的阻滞因子与土层的粘粒含量呈显著正相关;黑土对钾运移的阻滞作用是土壤质地、有机质含量、矿物组成等因子综合作用的结果。土娄土和黑土的扩散、弥散系数与平均孔隙水流速均呈极显著的线性关系。

长期施用化肥和稻草对双季稻田钾素运移的影响

以红壤双季稻区长期（1981-2012年）定位施肥试验为基础,研究长期施用化肥和稻草对双季水稻（Zea mays L.）集约化种植下3年期间（2010-2012年）水稻产量、作物吸钾量、田面水和不同土层渗漏水中钾动态变化及钾素平衡的影响。结果表明,施钾肥能增加水稻稻谷和稻草的产量;水稻从土壤中的吸钾量随钾肥施用量的增加而显著增加,年平均吸钾量顺序为NPK＋RS〉NPK〉NP＋RS〉CK〉NP;各处理田面水的钾浓度差异主要表现在施肥后前40d,早、晚稻中田面水的钾浓度随施肥时间的延长,逐渐下降,施肥后第40天,各处理田面水的钾浓度高低差异不大,早稻在2.34-3.43mg/L之间,晚稻2.03-2.97mg/L之间;3个施钾处理不同深度土层渗漏水钾浓度均随施肥时间的延长而逐渐下降,而不施钾肥的NP和CK两处理随施肥时间的延长变化幅度较小;在水稻施肥后的70d期间,3个施钾处理随着土层深度的增加,渗漏水钾浓度呈下降的变化趋势;早、晚稻3个土层各处理不同时间渗漏水平均钾浓度的高低顺序均为NPK＋RS〉NPK〉NP＋RS〉CK〉NP;除NPK＋RS处理处于钾盈余外,其他4个处理均处于钾素亏缺。试验结果说明,在施氮磷肥的基础上,配施钾肥和稻草还田不仅能提高水稻高产、稳产的能力,而且对促进钾素养分循环,保持农田钾素平衡,提高土壤钾素肥力有重要的作用。

有沙层土柱中钾离子运移的试验研究

通过室内有沙层土柱入渗中钾离子运移试验,研究了有沙层土柱中钾离子随入渗水运移的过程和特性。结果表明,入渗过程中,由于沙层阻水造成钾离子在沙层以上积累,而在沙层内钾离子浓度并不增加。经平衡计算和有无沙层试验比较表明,粗沙基本不吸附钾离子,因沙层阻水而使钾离子暂时滞留在土-沙界面上,随水量增大钾离子浓度锋透过沙层。因此,干旱区农田洗盐需要一定水量并持续一定时间,方能使盐锋达到沙层以下,起到抑制盐分的作用。

Bio-Mobilization of Potassium from Clay Minerals: I. By Ectomycorrhizas

A pot experiment was carried out to investigate effect of ectomycorrhizal fungi on eucalyptus growth and K bio-mobilization from soils and clay minerals. In the experiment, sands mixed with soil, KCI-saturated vermiculate and mica, respectively, were used to nurse eucalyptus seedlings which were nonectomycorrhized or ectomycorrhized by an ectomycorrhizal fungus Pisolithus tinctorius strain XCI (Pt XC1) isolated from a forest soil from Xichang, Sichuan Province, China, and a worldwide well-known ectomycorrhizal fungus Pisolithus tinctorius strain 2144 (Pt 2144) obtained in Australia. More depletion of HCl-soluble K by mycorrhizas from the soil and minerals than nonmycorrhizas suggested that mycorrhizas had a great ability to mobilize K present in the interlayer and feldspar. Mycorrhizal seedlings depressed greatly K digested with HF-HCIO4 from substrates after consecutive extractions of soils and minerals by water, ammonium cetate and boiling HCl, while nonmycorrhizal seedlings reduced it little if any, showing that the mycorrhizal seedlings could mobilize and then utilize the structural K in mineral lattice. Ectomycorrhizal fungi played a very important role not only in promoting the growth of eucalyptus seedlings but also in mobilizing K in soils and minerals. The infection of Pt XC1 led to a better growth of eucalyptus seedlings and more K accumulation in the seedlings than that of Pt 2144. The large differences in K accumulation by the seedlings might be due to different abilities of the two ectomycorrhizal fungi to mobilize K in interlayer and lattice pools in the clay minerals.

Quantitative Effect of Soil Texture Composition on Retardation Factor of K^+ Transport

With six packed columns composed of < 1 μm and 5 μm～0.25 mm fractions from an Eum-Orthic An- throsol (Columns 1～6) and one column of the Eum-Orthic Anthrosol (Column 7), K～(+) transport experiments under the condition of saturated steady water flow were conducted to qualify the effects of soil texture com- position on the retardation factor (R) of K～(+) transport. The results showed that the retardation factor of K～ (+) transport in the tested soil columns greatly increased with increasing clay contents. In an attempt to use pedo-transfer function (PTF) approach in the solute transport study, a preliminary PTF was established through the six packed columns (Columns 1～6) with soil basic data including soil bulk density, volumet- ric water content and clay content to predict the retardation factor, and proved valid by the satisfactory prediction of R in Column 7.

Bio-Mobilization of Potassium from Clay Minerals: Ⅱ. By Ectomycorrhizal Fungi

Ectomycorrhizal fungi, including Cenococcum geophilum SIV (Cg SIV), and Pisolithus tinctorius 2144 (Pt 2144), 441 (Pt 441) and XC1 (Pt XC1), were cultured in Pachlewski liquid medium with H2KPO4,KCl- saturated vermiculite and mica as K sources, respectively, to investigate the mechanism of K absorption and mobilization by the fungi. Fungal growth rate, K absorption and mobilization varied significantly among the fungal species. Faster growth and greater K accumulation in Pt XC1 than Pt 2 144, Pt 441 and Cg siv were observed. Ectomycorrhizal fungi depressed HCl-soluble K in minerals after successive extractions by water and NH4OAc. Ratio of the total amount of K, including water-, NH4OAc- and HCI-soluble K, lost from substrates to the K accumulated in fungal colonies was less than 60%. These reveal that the ectomycorrhizal fungi could utilize K in interlayer and structural pools, which are usually unavailable for plants in short period. Large differences in the depletion of K in interlayer and structural pools by fungi were observed at fungal harvest. Taking into account the nutrient absorption by ectomycorrhizal fungi in symbionts and the direct contact between hyphae and soils, the fungi species colonized on the root surfaces seemed to be related to the effectiveness of mycorrhizas to utilize K in soils. Ectomycorrhizal fungi differed in the efflux of protons and oxalate. Pt XC1 was observed to have greatest ability to effuse protons and oxalate among the fungi adopted in the experiment. Furthermore, the higher the concentrations of protons and oxalate in the liquid culture solutions, the larger the depletion of K in interlayer and structural pools in minerals by fungi. Protons could replace interlayer K and chelation of oxalate with Fe and Al in crystal lattice could cause weathering of clay minerals. So, protons and oxalate produced by ectomycorrhizal fungi might play an important role in K mobilization in these two pools.