Effects of Combined Application of Water Retaining Agents and Organic Materials on Water Holding Characteristics of Yellow Brown Soils in Hilly Areas

[Objective] The aim was to reduce fertilizer and water losses caused by surface runoffs in rainy season and provide scientific references for soil moisture in arid season. [Method] The application proportion of complex water-holding organic materials was determined by multi-factor mixture experiment and the curve changes of soil moisture characters were tested to analyze water-holding capacity and water availability of soils. [Result] The initial moisture content of soil with different mixture proportions improved in varying degrees. For example, when water-retention agents reached 0.4% and 0.6% of soil weight, soil moisture contents were 69.0% and70.5%, respectively, which showed significant differences with the control（S0.0）. Soil dehydration terms in different treatments all extended, prolonging in the range of4.6-14 d. [Conclusion] The applications of water-retention agent and organic material would improve water-holding capacity of hills and low mountains, and initial moisture content and dehydration cycle tend to be volatile upon mixture proportion. Therefore,it is necessary to adjust soil fertility, crop species, and irrigation to meet crop demands on fertilizer and water.

Potential Role of Feldspathic Sandstone as a Natural Water Retaining Agent in Mu Us Sandy Land,Northwest China

This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land. The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased, the soil texture changed from sand to silt loam, the capillary po- rosity gradually increased from 26.3% to 44.9%, and the soil saturated hydraulic conductivity decreased from 7.10 ram/rain to 0.07 mm/min. Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil, playing the role of a ＇water absorbent＇ and ＇water retaining agent＇ in sandy land. Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%. This study provides a theoretical basis for the amelioration of sandy land on a large scale. It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.

Discussion of Fenlong Cultivation Supporting Food and Environment Safety and Broadening Survival and Development Space

A new high-efficiency farming method of global significance, Fenlong tech- nique capable of making soil fertile, increasing yield and improving ecological envi- ronment was introduced; and the Fenlong technique could deeply plough and scarify soil with a depth up to 30-50 cm, which is deeper than the depth of tractor tillage, solving the problem of difficulties in deeply ploughing and scarifying soil and keeping soil loose for muttiple seasons. The application to 20 crops in 18 provinces proved that yield could be increased by 10%-30% without increase in chemical fertilizer, quality could be improved by more than 5%, and water storage could be increased by 100%; yield could be increased for multiple seasons sustainably, and the yield of dry-land crops increased by 32.57%-38.2% from the second year to the fourth year; the net benefits of rice increased by 21.82% averagely from the first season to the sixth season; and the usage amount of chemical fertilizer decreased by 0.35-4.29 kg per 100 kg produced grain compared with conventional tillage, with an decrease amplitude of 10.81%-30.99%. It was discussed that the Fenlong technique could maximize friendly permanently-sustainable unitization of ＂natural resources＂ including soil nutrients, water, oxygen and light energy, and has good development potential in multiple fields. It was put forward that if it is popularized in 0.67x108 hm2, pro- ductivity of farmland could be newly increased by 0.1-0.13×10^8 hm2, 5.0 ×10^6 t of chemical fertilizer could be saved, the＇ storage of agricultural water could be in- creased by 3.0×10^10 m3, and increased food could feed 2,0-3.0×10^8 people.

Self-centring segmental retaining walls—A new construction system for retaining walls

This paper reports on an experimental study on a new self-centring retaining wall system.Four post-tensioned segmental retaining walls(PSRWs)were experimentally tested.Each of the walls was constructed using seven T-shaped concrete segments with a dry stack.The walls were tested under incrementally increasing cyclic lateral load.The effect of the wall height,levels of post-tensioning(PT)force,and bonded versus unbonded condition of PT reinforcement on the structural behavior of the PSRWs was investigated.The results showed that such PSRWs are structurally adequate for water retaining structures.According to the results,increasing the wall height decreases initial strength but increases the deformation capacity of the wall.The larger deformation capacity and ductility of PSRW make it a suitable structural system for fluctuating loads or deformation,e.g.,seawall.It was also found that increasing the PT force increases the wall’s stiffness;however,reduces its ductility.The residual drift and the extent of damage of the unbonded PSRWs were significantly smaller than those of the bonded ones.Results suggest that this newly developed self-centring retaining wall can be a suitable structural system to retain lateral loads.Due to its unique deformation capacity and self-centring behavior,it can potentially be used for seawall application.