Photosynthetic characteristics and nitrogen distribution of large-spike wheat in Northwest China

The leaf photosynthesis and nitrogen（N） translocation in three large-spike lines and control cultivar（Xi＇nong 979） of winter wheat（Triticum aestivum L.） were studied in 2010–2011 and 2011–2012. The objectives of this study were to investigate the differences in the physiological characteristics of large-spike lines and control cultivar and identify the limiting factors that play a role in improving the yield of breeding materials. The average yield, grain number per spike, kernel weight per spike, and 1 000-kernel weight of the large-spike lines were 16.0, 26.8, 42.6, and 15.4%, respectively, significantly higher than those of control. The average photosynthetic rates（Pn） were not significant between the large-spike lines and control cultivar during the active growth period. The average PSII maximum energy conversion efficiency（Fv/Fm）, PSII actual quantum efficiency（Ф（PSII））, photochemical quenching coefficient（qP）, PSII reaction center activity（Fv′/Fm′） and water-use efficiency（WUE） of the large-spike lines were 1.0, 5.1, 3.6, 0.8, and 43.4%, respectively, higher than those of the control during the active growth stages. The N distribution proportions in different tissues were ranked in the order of grains〉culms＋sheathes〉rachis＋glumes〉flag leaves〉penultimate leaves〉remain leaves. This study suggested that utilization of the large-spike wheat might be a promising approach to obtain higher grain yield in Northwest China.

Effects of Irrigation on Soil and Wheat Yield under Drought Conditions in Sichuan

In order to study the effective water-saving cultivation of wheat in Sichuan under drought conditions to reduce grain loss,the effects of different irrigation methods（ natural rainfall,artificial irrigation,and infiltrating irrigation） on soil physical characteristics and main agronomic characters and yield of wheat were analyzed. The results showed that different irrigation treatments at different growth stages had different effects on soil physical characteristics and agronomic characters of wheat. At the seedling and jointing stage,there were small differences between the treatments in soil compactness,soil bulk density,and soil water content. At the flowering and maturation stage,different irrigation treatments had great impacts on soil compactness,soil bulk density,soil water content,and agronomic characters of wheat. In the hilly areas of Sichuan Basin,infiltrating irrigation at the jointing stage was the best,and wheat yield increased significantly,2 113. 46 kg/hm^2 higher than that in the control.

Influence of laser shock peening on surface integrity and tensile property of high strength low alloy steel

Laser Shock Peening(LSP)is a well-established surface treatment commonly used to improve mechanical properties of material’s surfaces.To further understand the relationship between tensile property and fatigue life improvement of high strength low alloy steel in the LSP process,LSP treatment of 32 CrNi high strength low alloy steel was carried out by YAG laser with pulse energy of 15 J,and tensile property was tested by electronic universal material testing machine.Surface morphology,residual stress and tensile fracture of the specimens before and after LSP were observed by white light interferometer(WLI),X-ray measuring apparatus and scanning electron microscope(SEM).Result shows that LSP did not change tensile strength of 32 CrNi steel but cause yield characteristic transform from obvious yield point to no yield phenomenon which is the only factor benefiting fatigue life,indicating that the increment of fatigue life was probably related to the disappearance of yield phenomenon.Formation mechanisms of tensile fractures and yield phenomenon induced by LSP at room temperature were also discussed and completely revealed.Deeper compressive residual stress and flat grains contributed to the transition of yield characteristic and lower elongation rate of 32 CrNi steel subjected to LSP.

Crop Insurance Premium Ratemaking Based on Survey Data:A Case Study from Dingxing County, China

Premium ratemaking is an important issue to guarantee insurance balance of payments. Most ratemaking methods require large samples of long-term loss data or farm-level yield data, which are often unavailable in developing countries. This study develops a crop insurance ratemaking method with survey data. The method involves a questionnaire survey on characteristic yield information(average yield, high yield, and low yield) of farming households’ cropland. After compensating for random error, the probability distributions of farm-level yields are simulated with characteristic yields based on the linear additive model. The premium rate is calculated based on Monte Carlo yield simulation results. This method was applied to Dingxing County, North China to arrive at the insurance loss cost ratio and calculate the necessary premium rate. The method proposed in this study could serve as a feasible technique for crop insurance ratemaking inregions that lack sufficient long-term yield data, especially in developing countries with smallholder agriculture.