Cultivation effects on temporal changes of organic carbon and aggregate stability in desert soils of Hexi Corridor region in China

Sustainable agricultural use of cultivated desert soils has become a concern in Hexi Corridor in Gansu Province of China, because loss of topsoil in dust storms has been recently intensified. We chose four desert sites to investigate the effects of cultivation (cropping) on (i) soil organic C and its size fractions and (ii) soil aggregate stability (as a measure of soil erodibility). These parameters are of vital importance for evaluating the sustainability of agricultural practices.

Total organic C as well as organic C fractions in soil (coarse organic C, 0.1–2 mm; young organic C, 0.05–0.1 mm; stable organic C, <0.05 mm) generally increased with the duration of the cultivation period from 0 (virgin soil, non-cultivated) to more than 30 years (p < 0.05). Compared to total organic C in virgin soils (2.3–3.5 g kg⁻¹ soil), significantly greater values were found after 10 to >20 years of cultivation (6.2–7.1 g kg⁻¹ soil). The increase in organic C in desert soils following prolonged cultivation was mainly the consequence of an increase in the coarse organic C. The increase in total organic C in soil was also dependent on clay content [total organic C = 0.96 + 0.249 clay content (%) + 0.05 cultivation year, R² = 0.48, n = 27, p < 0.001]. This indicates that clay protected soil organic C from mineralization, and also contributed to the increase in soil organic C as time of cultivation increased.

There was a significant positive correlation between aggregate stability and total organic C across all field sites. The water stability of aggregates was low (with water-stable aggregate percentage 4% of dry-sieved aggregates of size 1–5 mm). There was no consistent pattern of increase in the soil aggregate stability with time of cultivation at different locations, suggesting that desert soils might remain prone to wind erosion even after 50 years of cultivation. Alternative management options, such as retaining harvested crop residues on soil surface and excluding or minimizing tillage, may permit sustainable agricultural use of desert soils.     

农户社会经济特征对农业种植意愿的影响* ——基于农业文化遗产保护目的的福州茉莉种植户研究

因城市用地侵占和种植成本增加等原因,福州茉莉花种植面积锐减,严重威胁到重要农业文化遗产——福州茉莉花与茶文化系统的持续性。保证茉莉种植可持续性的根本在于花农种植意愿及其影响因素,据此制定有针对性的保护措施。本研究通过问卷调查和农户访谈获取花农社会经济特征及其对茉莉种植意愿的数据,使用描述统计法对调查农户的社会经济特征进行分析,使用二元Logistic回归分析法分析花农社会基本特征(性别、年龄、受教育程度、获取信息手段、对茉莉花用途的认识深度)和经济特征(当前茉莉单位面积收益、种植者收入在熟悉人群的位置、种植者希望茉莉花单位面积收益)与其种植意愿的关系,找出影响农户种植意愿的主要因素。结果表明:花农群体呈老龄化趋势,受教育水平普遍偏低,获取信息方式较落后单一;对茉莉花的综合认知水平整体不高,一半以上的花农打算继续种植茉莉花;花农掌握信息能力和对茉莉单位面积收入的预期是影响花农是否愿意继续种植的两个主要因素。保证茉莉种植业可持续发展的主要途径包括:提高茉莉种植补贴、通过政策倾斜吸纳青年人才经营茉莉产业,建立种植业的可持续机制;推动企业与农户、农户与农户的合作,稳定种植业收入;充分利用茉莉种植业的多功能性,发展旅游业、休闲农业等多种产业模式;借鉴传统种植技术原理,研发高效的生产设备,提高茉莉种植的生产效率,以降低劳动强度和增加农户收入;加强对花农的农业文化遗产保护与利用知识普及和传统种植技术培训,提高自我发展能力;开设中小学生农业文化遗产文化课和遗产地教育实践课,增进他们对于茉莉花与茶文化系统的感情与保护意识。     

The effect of humic acids on the availability of phosphorus fertilizers in alkaline soils

Abstract. The effect of humic acids on transformation of phosphorus fertilizer was studied in an alkaline soil. Soil P was fractionated following 4 and 15 days incubation after humic acids were applied with phosphorus fertilizer to the soil. The availability of phosphate in the soil and total phosphorus in plants were determined at earing stage and at maturity in a pot experiment, and wheat yield was examined in a field trial. Addition of humic acids to soil with P fertilizer significantly increased the amount of water soluble phosphate, strongly retarded the formation of occluded phosphate and increased P uptake and yield by 25%.