等高植物篱种植模式及其应用中存在的问题

等高植物篱技术是一种坡耕地上低投入、高收益的保护性耕作和持续利用技术。坡耕地采用植物篱种植模式进行水土保持和生态环境治理,能达到明显的保水保土效果,同时能产生显著的经济效益和社会效益。但其推广应用效果不理想,这是因为实施前期收益不明显,作物产量提高滞后,农户管理水平低等因素阻碍了这项水土保持措施的实施。因此,要实施该项技术,应筛选经济价值高的植物篱品种,科学规划篱笆带间距和种植密度,立足山区实际开展技术培训,多渠道筹措资金等。     

冀南地区蔬菜保护地土壤养分变化特点

对冀南地区蔬菜保护地土壤养分现状及变化趋势进行了研究，结果表明，保护地耕层土壤有机质、土壤速效N、速效P和速效K比相邻露地栽培分别平均增加146．64％、51．68％、567．17％和110．41％；比1981年土壤分别增加143．23％、97．97％、2311．00％和98.8％。随栽培年限的增加，耕层土壤速效N、速效P和速效K有积累的趋势，土壤养分主要积累在0～20cm土层，随着土层加深土壤养分积累程度降低，其中以日光温室栽培的土壤养分积累高于塑料大棚。     

Efficiency and energy use in puddling of lowland rice grown on Vertisols in Central India

Transplanting of rice seedling in puddled soil is one of the most widely used cultivation practices. The present research is aimed at determining what specific implements are needed to obtain optimal puddle bed for transplantating. Puddling experiments were carried out by the use of pair of bullocks with traditional country plough (T₁), pair of bullocks with lug wheel puddler (T₂), power tiller with rotary puddler (T₃), tractor with cage wheel and 9-tine cultivator (T₄) and tractor with cage wheel and rotavator (T₅). One summer ploughing was done at friable moisture condition (18.6% db) and then tilled soil was flooded to saturation (24 h) for preparation of puddled bed. Weeding efficiency, puddling depth, percentage increase in bulk density, puddling index, percolation rate and grain yield of paddy were studied for the above treatments. Puddling performance by different implements in comparison to the traditional animal drawn country plough (T₁) shows that there is a definite reduction in time requirement for field preparation. Increase in weeding efficiency, bulk density, grain yield and puddling index were also observed. The highest values of weeding efficiency and puddling index were found 98.6% and 79.3, respectively, for rotavator (T₅). The total time requirement for preparation of puddle field for treatment T₄ (tractor with cultivator) was found to be the lowest (9.4 h ha⁻¹) with 67% weeding efficiency and 62.7 puddling index as compared to all other alternatives tested. Energy requirement for preparation of puddle field was found highest (2390 MJ ha⁻¹) for rotavator (T₅) followed by T₃, T₄, T₁, and T₂ treatments.     

Occurrence of Polycyclic Musks in Sewage Sludge and their Behaviour in Soils and Plants. Part 1: Behaviour of Polycyclic Musks in Sewage Sludge of Different Treatment Plants in Summer and Winter (5 pp)

Background, Aim and Scope   Part 1: Behaviour of Polycyclic Musks in Sewage Sludge of Different Treatment Plants in Summer and Winter Part 2: Investigation of Polycyclic Musks in Soils and Plants -  Preamble. In Part 1 of the study, screening tests were performed to investigate the occurrence of PCMs in sewage sludges. For a preliminary risk assessment, further information is needed about their behaviour in the terrestrial environment. Hence, Part 2 examined the adsorption of PCMs to soil, their dissipation and leaching in soil and their uptake by plants. Background, Aim and Scope   Polycyclic Musks (PCMs) enter the environment via the waste water system. Because of their persistence, they can accumulate in different matrices like sewage sludge or biota. By the use of sewage sludge as a fertilizer, PCMs are transferred to agricultural soils. Therefore, in Part 1 of the study, screening tests were performed to investigate the occurrence of PCMs in sewage sludge. For a preliminary risk assessment, further information is needed about their behaviour in the terrestrial environment. Hence, Part 2 of the study examined the adsorption of PCMs to soil, their dissipation and leaching in soil, and their uptake by plants. Materials and Methods: In the screening study, samples of activated sewage sludge were taken both in summer and in winter at 21 treatment plants. In order to get an overview of the contamination situation, sampling covered different types of treatment plants (in rural, urban, industrial areas). Analytical methods for the determination of HHCB, AHTN, ADBI, ATTN, AHDI and ATII in the sludge samples were developed and applied. Results: The analytical screening of PCMs showed their presence in activated and dried sewage sludge samples. HHCB and AHTN represented about 95% of the PCMs investigated. Their concentrations in the activated sludge samples varied between 2.9 and 10.4 mg/kg dry mass (dm) and 1.1 to 4.2 mg/kg dm, respectively. Although different types of sewage treatment plants were investigated, similar PCM levels were found, showing the widespread input of these compounds into domestic waste water. Discussion: PCM concentrations in activated sludge varied widely. The variation drops substantially when concentrations are related to the varying dry mass. In dehydrated sludge, PCM concentrations were up to 24 mg/kg dm for HHCB and up to 6.9 mg/kg dm for AHTN. These high values are comparable to those obtained in other investigations analysing PCMs. If the degradation of organic mass during anaerobic decomposition is included in the evaluation, the figures obtained are comparable to those for activated sludge. Elimination in sewage sludge was higher in summer than in winter. Therefore, the contamination of the sludges in winter reached higher levels compared to the summer. Conclusions: The results show that PCMs are widespread contaminants in sewage sludge. Recommendations and Perspectives: PCM should be considered in a risk assessment as potential contaminants of sewage sludge destined for agricultural use. Due to the high PCM levels in sewage sludge, further investigations into the degradation and elimination behaviour in sewage sludge have to be carried out, including that involving PCM metabolites such as lactone derivatives.     

多伦草原土壤理化性质在沙漠化过程中的变化

以典型生态脆弱区内蒙古多伦县为例,连续2 a进行了沙漠化对土壤理化性质的影响研究。结果表明,随着草原沙漠化的加剧,(1)土壤颗粒组成发生变化,黏粒含量趋于减少,砂粒增多。不同粒径对土壤团粒结构形成和保水保肥的贡献不同,黏粒的减少抑制了土壤的膨胀、可塑性及离子交换等物理性质。(2)土壤含水量下降。上层(0—20 cm)土壤含水量下降明显,随着沙漠化梯度的增加,表层土壤含水量下降速度加快,从而深层土壤含水量逐渐高于表层。(3)土壤容重呈上升趋势。容重的增加必然影响土壤中水分和空气的移动及植物根系的发育。不同深度的土壤容重与草原沙漠化也存在一定的关系,潜在阶段深土层(30—50 cm)的容重最小,而严重阶段表土层(0—5 cm)容重最小。(4)土壤有机质,C,N含量下降,方差分析显示各沙漠化梯度间均差异极显著。且土壤N的衰减要快于C。土壤C/N比呈增加趋势,说明伴随着土壤C,N的显著下降,质地变粗,植物N素供应不足更为突出。(5)土壤容重与土壤全N,C及黏粒含量的相关分析表明,细颗粒物多,有机质含量高,土壤容重即小,从而有助于提高土壤的稳定性,且5—10 cm土层的性质表现突出。(6)土壤的颗粒组成状况与土壤营养元素之间有着同增同减性,但黏粒与N的关系要密切于黏粒与C和C,N间的关系。因此土壤中细颗粒物的减少会导致N素的衰减十分明显,从而导致土壤稳定性降低。     

膜下滴灌棉花土壤水分动态变化研究

通过系统观察不同土壤类型棉花土壤水分动态变化规律，研究膜下滴灌棉花土壤水分的变化，以有效地提高棉花产量和水分利用效率。结果表明：膜下滴灌棉花土壤含水量呈现规律性的变化：在黏土地上，土壤含水量的变化趋势近似于抛物线，0～20cm土壤含水量最低，随土层深度增加，土壤含水量逐渐增加，至60-80cm达最大，随后又降低。而在沙土地，土壤含水量的变化趋势与黏土地相反。这种变化与土壤的理化、生物学特性以及棉花根系的生长发育有关。不同土壤类型膜下滴灌棉花产量、总耗水量及水分利用效率存在明显差异。     

白榆沙棘光合生理参数与土壤含水量关系研究

采用Li-6400便携式光合仪在模拟光照条件下，对不同水分处理的白榆、沙棘进行观测。观测参数包括：净光合速率、气孔导度、蒸腾速率、胞间CO2浓度等。并且运用SPSS数据处理软件进行分析，从而确定白榆、沙棘光合生理参数与土壤含水量之间的关系，并在研究过程中对试验地土壤水分进行有效性评价；其等级分别为：无产无效水、低产低效水、高产高效水、高产低效水。而把高产高效水作为指导当地林业生产的土壤水分管理条件。结果表明白榆沙棘具有高产高效的土壤含水量分别为11．4％～17．2％；9．5％～16．5％。     

黄土丘陵区不同降雨强度对农地土壤侵蚀的影响

采用人工模拟降雨的方法，对仪器自身性能进行了测试，并分设5种不同的降雨强度分别研究半干旱区林地、草地、人工草地和耕地的产流产沙特征。模拟天然降雨最大雨强5．05mm／min，雨量118．2～300．3mm／h；雨滴落地速度、雨滴动能等降雨特征值与天然降雨特征值是一致的；不同立地条件下径流量、侵蚀模数随雨强的增加而增加，并与降雨强度呈指数函数或幂函数关系。