Influence of salinity and moisture on the threshold shear velocity of saline sand in the Qarhan Desert,Qaidam Basin of China: A wind tunnel experiment

Determination of the threshold shear velocity is essential for predicting sand transport, dust release and desertification. In this study, a wind tunnel experiment was conducted to evaluate the influence of salinity and moisture on the threshold shear velocity of saline sand. Saline sand samples (mean particle size of 164.50-186.08 μm and the total silt, clay and salt content of 0.80%-8.25%) were collected from three saline sand dunes (one barchan dune and two linear dunes) in the Qarhan Desert, Qaidam Basin of China. Original saline sand samples were placed in two experimental trays for wet and dry processing to simulate deliquescence and desiccation, respectively. Surface moisture content ranging from 0.30% to 1.90% was generated by the steam method so that the saline sand can absorb water in a saturated water vapor environment. The motion of sand particles was determined by the observers with a solid laser. The laser sheet (0.80 cm thick), which was emitted by the solid laser, horizontally covered the sand surface and was bound to the sand. Results show that the cohesion of saline sand results from a combination of salt and water. The threshold shear velocity increases exponentially with the increase in crust thickness for the linear sand dunes. There is a positive linear correlation between the original moisture content and relative threshold shear velocity. The threshold shear velocity of dewatered sand is greater than that of wet sand with the same original moisture content. Our results will provide valuable information about the sand transport of highly saline soil in the desert.     

Reducing crude protein variability and maximizing savings when formulating corn-soybean meal-based feeds

Crude protein in corn and soybean meal have been documented to vary, and such inherent variability can result in under- or over-feeding of CP when feeds are formulated, leading to reduced bird growth, added input costs, and increased environmental pollution. The purpose of this study was to compare 2 grain-handling techniques and 2 feed formulation methods (linear vs. stochastic programming) to reduce CP variability in finished feeds and determine resulting costs or savings. The 2 grain-handling techniques were placing all the random batches of each delivered ingredient in to (1) a single bin (1-bin method) or (2) segregating above- and below-average samples into 2 bins (2-bin method). A fast way of estimating the composition of the ingredients is now available (near-infrared reflectance spectroscopy). Microsoft Excel workbooks were constructed to solve broiler starter feed formulation problems. Formulating feeds by linear and stochastic models based on the 2-bin method reduced CP variability by at least 50% compared with the 1-bin method. Formula cost was reduced by ˜20 cents per ton (averages of August 2012 United States ingredient prices) when the 2-bin method was used with the linear model. Formulating feed with a margin of safety increased formula cost by $3.40 per ton. Stochastic feed formulation increased formula cost to meet the specified CP level in feed at any probability of success, and formula cost was reduced substantially with the 2-bin method (up to $6.47 per ton). The magnitude of savings and reduced feed variability suggested that, regardless of the costs associated with building extra bins, the 2-bin method can be economically efficient in the long run. Therefore, it could be possible to split the batches of feed ingredients at a feed mill into above- or below-average bins before feed formulation to reduce CP variability and to maximize savings.     

Regional distribution of wheat yield and chemical fertilizer requirements in China

Quantification of currently attainable yield and fertilizer requirements can provide detailed information for assessing the food supply capacity and offer data support for agricultural decision-making. Datasets from a total of 5 408 field experiments were collected from 2000 to 2015 across the major wheat production regions in China to analyze the spatial distribution of wheat yield, the soil nutrient supply capacity(represented by relative yield, defined as the ratio of the yield under the omission of one of nitrogen(N), phosphorus(P) and potassium(K) to the yield under the full NPK fertilizer application), and N, P and K fertilizer requirements by combining the kriging interpolation method with the Nutrient Expert Decision Support System for Wheat. The results indicated that the average attainable yield was 6.4 t ha~(-1), with a coefficient of variation(CV) of 24.9% across all sites. The yields in North-central China(NCC) and the northern part of the Middle and Lower reaches of the Yangtze River(MLYR) were generally higher than 7 t ha~(-1), whereas the yields in Southwest China(SWC), Northeast China(NEC), and the eastern part of Northwest China(NWC) were usually less than 6 t ha~(-1). The precentage of area having a relative yield above 0.70, 0.85, and 0.85 for N, P, and K fertilizers accounted for 52.3, 74.7, and 95.9%, respectively. Variation existed in N, P, and K fertilizer requirements, with a CV of 24.8, 23.9, and 29.9%, respectively, across all sites. More fertilizer was needed in NCC and the northern part of the MLYR than in other regions. The average fertilizer requirement was 162, 72, and 57 kg ha~(-1) for N, P_2O_5, and K_2O fertilizers, respectively, across all sites. The incorporation of the spatial variation of attainable yield and fertilizer requirements into wheat production practices would benefit sustainable wheat production and environmental safety.     

Xylanase and xylo- oligosaccharide prebiotic improve the growth performance and concentration of potentially prebiotic oligosaccharides in the ileum of broiler chickens

ABSTRACT

1. The objective of this study was to investigate the effect of supplementing broiler diets with xylanase or xylo- oligosaccharide (XOS) on growth performance, the concentration of non-starch polysaccharide (NSP) hydrolysis products in the ileum and concentration of short chain fatty acids (SCFA) in the caeca of broiler chickens.

2. In total, 500 male Ross 308 broilers were used in this 29-day (d) study. The treatments were organised into a 2 × 2 plus 1 factorial arrangement consisting of two additives (xylanase or XOS) at two levels (low or high) plus a control treatment with no additives. This gave five treatments with 100 birds in each treatment group. The diets were slightly deficient in protein by 20 g/kg and energy by 1 MJ/kg.

3. On d 14 and 28, two birds per pen were euthanised, the caeca content collected and analysed for short chain fatty acid (SCFA) concentration. On d 29, six birds per pen were euthanised and ileal digesta were collected and analysed for the concentration of NSP fractions.

4. On d 14, caecal acetic acid, iso-butyric acid, iso-valeric acid, n-valeric acid and total SCFA concentrations were significantly greater (P ≤ 0.05) when diets were supplemented with XOS compared with xylanase.

5. Ileal concentration of arabinose, galactose and glucuronic acid (GlucA2) were significantly greater (P ≤ 0.05) in the insoluble NSP fraction when diets were supplemented with a high level of xylanase, compared with the control treatment. Ileal concentration of fructose was significantly greater (P ≤ 0.05) in the water soluble NSP when a high level of xylanase or low level of XOS were included in the diet compared with the control.

6. It was concluded that xylanase and XOS had similar effects on NSP concentration and SCFA in the caeca, although there was little effect on performance. This observation demonstrated further benefits of xylanase supplementation in wheat-based broiler diets beyond digesta viscosity reduction and the release of extra nutrients.     

Time‐lapse monitoring of soil water content using electromagnetic conductivity imaging

The volumetric soil water content (θ) is fundamental to agriculture because its spatiotemporal variation in soil affects the growth of plants. Unfortunately, the universally accepted thermogravimetric method for estimating volumetric soil water content is very labour intensive and time‐consuming for use in field‐scale monitoring. Electromagnetic (EM) induction instruments have proven to be useful in mapping the spatiotemporal variation of θ. However, depth‐specific variation in θ, which is important for irrigation management, has been little explored. The objective of this study was to develop a relationship between θ and estimates of true electrical conductivity (σ) and to use this relationship to develop time‐lapse images of soil θ beneath a centre‐pivot irrigated alfalfa (Medicago sativa L.) crop in San Jacinto, California, USA. We first measured the bulk apparent electrical conductivity (EC_a – mS/m) using a DUALEM‐421 over a period of 12 days after an irrigation event (i.e. days 1, 2, 3, 4, 6, 8 and 12). We used EM4Soil to generate EM conductivity images (EMCIs). We used a physical model to estimate θ from σ, accounting for soil tortuosity and pore water salinity, with a cross‐validation RMSE of 0.04 cm³/cm³. Testing the scenario where no soil information is available, we used a three‐parameter exponential model to relate θ to σ and then to map θ along the transect on different days. The results allowed us to monitor the spatiotemporal variations of θ across the surveyed area, over the 12‐day period. In this regard, we were able to map the soil close to field capacity (0.27 cm³/cm³) and approaching permanent wilting point (0.03 cm³/cm³). The time‐lapse θ monitoring approach, developed using EMCI, has implications for soil and water use and management and will potentially allow farmers and consultants to identify inefficiencies in water application rates and use. It can also be used as a research tool to potentially assist precision irrigation practices and to test the efficacy of different methods of irrigation in terms of water delivery and efficiency in water use in near real time.     

Biochar has little effect on soil dissolved organic carbon pool 5 years after biochar application under field condition

Biochar application can improve soil properties, such as increasing soil organic carbon content, soil pH and water content. These properties are important to soil dissolved organic carbon (DOC); however, the effects of biochar on DOC concentration and composition have received little research attention, especially several years after biochar application under field conditions. This study was conducted in a long‐term experimental field where the biochar was only applied once in 2009. The purpose of the study was to investigate the effect of different biochar application rates (0, 30, 60 and 90 t ha^?1) on the dynamics of soil water content, DOC concentration and DOC compositions (reducing sugar, soluble phenol and aromatics) over nine samplings during a 12‐month period in 2014. Our results showed that soil water content and DOC concentration varied from 7.1% to 14.5% and 59 to 230 mg C kg^?1 soil during the 12 months, respectively. However, the biochar application rates did not significantly (p > 0.05) affect soil water content, DOC concentration and DOC composition at the same sampling period. The DOC concentration across the biochar treatments was positively correlated to soil water content. Moreover, the DOC composition (reducing sugar, soluble phenol or aromatics) and their concentrations were positively correlated to the total DOC concentration. In addition, biochar did not affect soil bulk density, pH, saturated hydraulic conductivity and crop yields. The results indicated that some benefits of biochar to soil may not persist 5 years after the application of biochar under a field condition.     

土壤中缓效钾的批量快速测定

通过对NY/T 889—2004标准中前处理方法的改进,建立了批量、快速、准确测定的土壤中缓效钾的方法。以石墨消解代替油浴消煮测定标准土中的有效钾,以验证改进后方法的可行性。结果表明,改进后的方法一次可以测定36个样品,且3 min内沸腾时间对结果无显著影响。因此,改进后的方法操作简单、条件易控制、准确快速,能实现对土壤中缓效钾的批量、快速测定。     

Maize harvest index and water use efficiency can be improved by inhibition of gibberellin biosynthesis

Possibilities to improve maize harvest index and nutrient utilization efficiency by application of plant growth regulators were investigated. In container experiments, the effects of different growth regulators on the development of the maize (Zea mays L.) cultivars Pioneer 3906 and Fabregas were tested. Paclobutrazol (PAC) and chlorocholine chloride (CCC), two inhibitors of gibberellin biosynthesis, as well as gibberellic acid (GA₃) were applied at growth stage V5. Three weeks after application of PAC, shoot growth of both maize cultivars was strongly affected with a significant decrease in plant height in the PAC treatment by 44% and 36% for Pioneer 3906 and Fabregas, respectively. The growth‐retarded plants had higher leaf areas and reduced transpiration rates. The higher shoot growth after GA₃ application was accompanied by a reduction in leaf area and an increase in transpiration rate during 1 week before anthesis. CCC treatment showed no significant effects on plant height, leaf area and transpiration rate. The PAC‐treated cultivar Pioneer 3906 produced several cobs per plant, which were mainly barren at maturity. However, PAC application to Fabregas resulted in just one cob per plant with good kernel development and a grain yield, which was not significantly reduced in comparison with the control. With this similar grain yield in combination with a straw yield decrease of 32%, the harvest index was significantly improved by 12%. In addition, with PAC‐treated Fabregas plants, a 19% increased water use efficiency of the grain (WUE_grain) during the critical period of kernel setting was achieved. In this maize cultivar, CCC application also improved harvest index by 5%, but no effect on WUE_grain occurred. GA₃ treatment decreased harvest index of both maize cultivars, and it either reduced WUE_grain (Pioneer 3906) or showed no effect (Fabregas). Utilization efficiencies of N, P and K were not increased with growth regulator application, even in the PAC‐treated Fabregas plants with a significantly improved allocation of assimilates to the grain, mirrored by the higher harvest index. The results indicate that fertilizer applications must be adjusted to the reduced demand of growth‐retarded plants, most likely leading to higher nutrient utilization efficiencies.     

便携式XRF仪现场快速测定土壤中Pb的可行性研究

便携式XRF分析仪具有轻便、快速和可测对象较多与测量元素较广等特点而广泛应用于矿石、土壤等方面快速检测,但土壤的现场快速测定结果的准确性有待进一步研究与探讨。以安宁河谷平原土壤中Pb为研究对象,通过对便携式XRF仪现场快速检测结果与实验室分析结果的对比和影响因素的分析,建立基于安宁河谷平原表层土壤快速测定结果的线性函数为y=1.170 9x-17.326 0(R~2=0.992 9,x为现场检测结果),探讨其影响因素,为该区域表层土壤中Pb快速检测结果提供依据。