Sites and processes of nutrient accumulation in the subsoil through water percolation from the plow layer in a submerged paddy soil microcosm

The leaching of nutrients from the plow layer by water percolation and their accumulation in the subsoil observed in a Japanese paddy field (Katoh et al. 2004: Soil Sci. Plant Nutr., 50, 721-729) were determined semi-quantitatively in a soil column experiment. Ca²⁺, Mg²⁺, K⁺, Mn²⁺, Fe²⁺, and phosphate in percolating water from the plow layer soil column were retained in the subsoil columns that were connected to the plow layer soil column. Fe²⁺, K⁺, and phosphate accumulated in the uppermost part of the subsoil. Accumulation of Fe²⁺ in the uppermost part of the subsoil was presmnably due to the cation exchange process with concomitant desorption of Ca²⁺. In contrast, Ca²⁺ and Mg²⁺ in percolating water from the plow layer soil colmnn accumulated once in the subsoil, and translocated downwards slowly with successive water percolation. Considerable amounts of inorganic carbon (IC) and dissolved organic carbon (DOC) in percolating water from the plow layer soil column were also retained in the subsoil columns. IC did not accumulate a gaseous form.     

施肥深度对生土地玉米根系及根际土壤 肥力垂直分布的影响

为探明施肥深度对生土地玉米(Zea mays L.)地上部生产力、根系及根际土壤肥力的影响,连续2年以黄土母质生土为供试土壤,采用根管土柱法,以不施肥为对照,研究不同深度(0~20 cm、60~80 cm、100~120 cm、140~160 cm和180~200 cm)施用生物有机肥对玉米地上部生产力及根重、根际土壤酶活性、根际土壤养分含量垂直分布的影响。结果表明:1)在0~200 cm土层范围内,随施肥深度的加深,玉米地上部生产力、总根重等指标均呈先增加后减少的规律。施肥深度在100~120 cm处的玉米总根重(52.3 g)及地上部生产力(361.0 g)最大。2)所有施肥深度的根重垂直分布均呈"T"型,以0~20 cm耕层根重最大,占总根重的50%左右,随根系下延,根重明显递减(P0.05)。施肥深度100~120 cm可以获得最大总根重和0~40 cm耕层根重(27.19 g)。根系N、P和K养分积累适中,平均分别为6.60 g·kg~(-1)、2.38 g·kg~(-1)和8.16 g·kg~(-1)。3)施肥明显提高根际土壤酶活性和养分含量。施肥深度为60~80 cm,0~200 cm土层根际土壤脲酶活性较高,介于0.108~0.354 mg(NH3-N)·g~(-1)(soil)·24h~(~(-1));施肥深度为140~160 cm时,0~200 cm土层根际土壤蔗糖酶活性和速效磷含量较高,分别为12.9~19.6 mg(glucose)·g~(-1)(soil)·24h~(-1)和4.31~6.02 mg·kg~(-1);施肥深度180~200 cm,0~200 cm土层根际土壤有机质含量较高,介于5.55~7.14 g·kg~(-1);施肥深度小于100 cm或大于120 cm,0~20 cm土层根际土壤碱性磷酸酶活性和碱解氮含量较高,分别0.497 mg(phenol)·g~(-1)(soil)·24h~(-1)和25.4 mg·kg~(-1)。4)相关分析表明,在生土地上,不同施肥深度处理下,玉米根重、根系NPK营养、根际土壤酶活性及根际土壤NPK营养密切相关。5)根据FACTOR过程和CLUSTER聚类分析,优化得出改良黄土母质生土地玉米冠-根-土系统的适合施肥深度范围为60~160 cm。本研究结果为通过施肥加快生土熟化提供了新的思路。     

玉米施水播种增加灌水下渗的松土方法和试验

研究了下插式土壤松耕方法,分析了其工作原理、理想的刀具结构和合适的松土距离为50～70 mm,并用这种方法松土后进行了施水试验。结果表明：灌水入渗深度比未耕地或旋耕地对应值平均增加20 mm以上,且土壤湿润区整体下移约13 mm,灌水水平方向和垂直方向入渗深度的比值由1.3降低到0.8,而且,土壤紧实度和含水率均满足玉米施水播种的需要。这种方法有效增加了玉米施水播种灌溉水的下渗深度,减少了水分蒸发。     

三段式心土混层犁及其改良白浆土效果的研究

三段式心土混层犁为改造白浆土土体构型实现了“上翻20 cm，下混30～40 cm”的农艺要求，白浆层与淀积层的土壤混拌率M_x达到0.7，白浆层向淀积层的土壤转移率T_Aw→B达到了0.3。0～40 cm土层土壤物理性状明显改善，疏松透水，硬度下降，农田表涝现象得到缓解，效果持久稳定，连续4年测定，耕翻一次后至第4年其土壤硬度仍然明显低于常规耕作田块。1996年～1998年大面积示范试验，使用该犁耕翻地块作物增产达10%～27.9%。该犁作业幅宽50 cm，深度60 cm，总牵引阻力30～35 kN。     

渡槽纠偏新技术——地基应力解除法

地基应力解除法是一项新的建筑物纠偏技术,它和一般的掏土法有根本区别。自1989年5月以来,已运用该法在武汉市成功地纠正了15座倾斜楼房,并于1991年2月2日通过了湖北省科学技术成果鉴定。本文通过对一座渡槽的排架纠偏,证明了该法对渡糟这一类水工建筑物也可取得良好的效果。     

运动荷载作用下Vlazov地基上梁的动力分析

采用Vlazov地基模型,研究了运动荷载作用下弹性地基上梁的动力响应问题.运用Fourier积分变换和留数定理对动力控制方程进行求解,得到了平面应变条件下覆盖于基岩的均质弹性层和非均质弹性层地基上梁的动力响应解析解,并进一步分析了荷载运动速度、地基厚度及地基非均质性等对梁变形的影响规律.研究结果表明,荷载运动速度、地基厚度及地基土的非均质性对梁的变形影响较大.     

降香黄檀种子贮藏及播前处理技术

经4种方法处理后测定降香黄檀种子发芽率,运用3种方式贮藏后播种测定降香黄檀的种子发芽率。播种后,用3种基质覆盖测发芽率和成苗率。结果表明播种前用60℃温水加高锰酸钾消毒30 min,再浸泡24 h的种子发芽率最高;17℃贮藏最适合规模育苗;用黄心土作为基质覆盖,效果最好。     

玉米深松全层施肥精量播种机的设计

设计了一种玉米深松全层施肥精量播种机。该机具进地一次可完成深松、全层施肥、精量播种、覆土和镇压等多项作业,并能打破犁底层,疏松土壤,全层施肥,减少机具多次进地对土壤产生的压实。玉米深松全层施肥精量播种机在深松的同时,将作物生长所需肥料一次性分施在土壤下的10～25㎝的区间内,以确保玉米在生长过程中有充足的肥料,提高肥料的利用率,不需追肥。     

Soil Organic Matter Composition in Coastal and Continental Date Palm Systems: Insights from Tunisian Oases

In Tunisia, the coastal Chenini oasis is characterized by a lush vegetation cover, whereas more inland continental oases (e.g., the Guettaya oasis) have a very scarce vegetation cover. For sustaining date palm production in these areas, organic fertilizers are applied, either spread on the soil surface (in Chenini) or buried under a sand layer (in Guettaya). We examined at a molecular level how these management techniques affect soil organic matter composition in oasis systems. A dominance of fresh plant input for Guettaya was indicated by solid-state ¹³C nuclear magnetic resonance spectroscopy signals, which was most pronounced in the uppermost soil close to palms. Evidence for more degraded organic matter was found in deeper soil near the palms, as well as in the soil distant from the palms. Amino sugar contents were low in the uppermost Guettaya soil near the palms. The overall microbial amino sugar residue contents were similar in range as those found in other dryland environments. With increasing distance from trees, the amino sugar contents declined in Guettaya, where the palms grow on bare soil, but this was not the case for Chenini, which has multi-layer vegetation cover under palms. In agreement with the results from previous dryland studies, the soil microbial community in both oasis systems was dominated by fungi in topsoil, and a shift toward bacteria-derived residues in subsurface soil. This might be due to higher variability of temperature and moisture in topsoil and/or lower degradability of fungal remains; however, further research is required to confirm this hypothesis.