Heavy Metal Content in Chinese Vegetable Plantation Land Soils and Related Source Analysis

According to the previous literature published since 1989, statistical analysis for reported data on the heavy metals in Chinese vegetable plantation soils was carried out systematically in this article. The purpose of this investigation was to study the status of heavy metal content in vegetable land soils systematically through objective assessment to promote the development of vegetable production with high quality and efficiency. It is concluded that Zn, Cr, Cu had relatively high concentrations while the mean concentrations of toxic metals, As, Hg, Cd were 8.03, 0.12, 0.28 mg·kg^-1, respectively with comparatively low concentrations in Chinese vegetable land. Comparing to Clainese Soil Quality Criterion GB 15618- 1995 （6.5 〈 pH 〈 7.5）, about 24.1, 10.3, and 9.2% of the total samples was contaminated by Cd, Hg, and As, respectively, and the descending order of heavy metals was Cd 〉 Hg 〉 As 〉 Zn 〉 Cu 〉 Cr 〉 Pb. When compared among different regions, the more serious heavy metal contamination was found in the vegetable land of eastern China and the main contamination elements were Cd, Hg, and Zn. In the mid region, vegetable plantation land soil was mainly polluted by As and Cd, as well as by Hg, Zn, and Cu, to some extent. In the west region of China, Cd and As contamination was also observed to some degree, along with few soil samples exceeding the grade Ⅱ level of GB 15618-1995 （6.5 〈 pH 〈 7.5） for Cu, Cr, and Hg content. Compared to the five vegetable plantation land patterns, the highest concentration of As, Cd, Hg, and Zn occurred in the industrial/sewage irrigation vegetable land, especially for Hg with 2.36 mg·kg^-1 content averagely, which is 10.5-21.1 times higher than the other four types of vegetable lands. The highest concentration of Cn and Cr occurred in the greenhouse vegetable land soils, and urban vegetable land soil had the highest Pb content in comparison with the other types of vegetable plantation land patterns. By analyzing heavy metal content under differe     

预防地膜棉早衰早死措施

威县地处冀南平原,是国家优质棉基地县,年种植地膜棉60多万亩,近年地膜棉花早衰早死现象严重,每年不同程度的早衰早死面积10万亩左右,平均亩减产籽棉50kg左右,损失严重。根据威县的生态条件和地膜棉花的生育特点,既防止早衰早死,又保证及早成熟的主要措施是:1轮作倒茬,清洁棉田     

无公害玉米栽培技术

一、选地与整地玉米是喜肥水的作物,在土壤肥力较高的地块种植更能发挥其增产潜力。因此应选择中等肥力以上、土壤疏松的地块种植,忌重茬。种植地块应在前茬作物收获后,及时进行深松作业,深松深度30～35cm。松后采用重耙耙透、耙细、耙碎,如有条件可采用秋起垄夹肥,达播种状态。二、合理施肥玉米是需肥较多的作物,施N、P、K纯量比为1∶1.5∶0.3。一般公顷施尿素90kg作基肥,在玉米拔节期或大喇叭口期公顷追施尿素75kg,增产效果显著,可减少玉米秃尖,保证了玉米生育中后期氮肥的均衡供应。     

马铃薯高产栽培技术

1品种选择 根据种植地的环境条件、气候特点及种植季节来选择不同适应的品种。种薯质量要求纯度高、芽眼充实、健康无病虫、新鲜无破伤的抗病、优质、高产、商品性好的优良品种。目前,塔城选用品种为垄薯5号、垄薯6号、新大坪等品种。     

生如夏花

2008年的春天,我们来到了云南大理鹤庆的黄坪镇。虽说这里是一个名不见经传的小镇,但街道干净,铺面整齐,整个空间充满了都市所没有的宁静与和谐。美中不足的是环抱这个小镇的不是植被丰厚的巍峨群山,而是已被人为破坏了的难寻绿色的荒山,满眼的凄