Assessment of uncertainty and sensitivity analyses for ORYZA model under different ranges of parameter variation

We explore the effects of different ranges of parameter variation (RPV) on sensitivity and uncertainty analyses for ORYZA_V3 model. In this study, a latin hypercube sampling (LHS) technique is used to generate parameter sample sets, and a regression-based method is employed for the sensitivity analysis on 16 crop parameters. Then, a top-down concordance coefficient (TDCC) is calculated to assess the stability of parameter sensitivity rankings across diverse RPV. Furthermore, coefficients of variation (CV) and 90% confidence intervals (90CI) of daily model outputs are analyzed by considering uncertainty in observations. We find that the increasing RPV multiplies the CV of daily model outputs, whereas the RPV has no effect on the CV’s change rule over time. The 90CI of model outputs include most of the observations when the RPV is more than ±30% perturbation. The standardized regression coefficient (SRC) of some parameters are obviously minified when the RPV is ±5% or ±50% perturbation. The results highlights the importance of RPV selection in the sensitivity and uncertainty analysis of crop model, and ±30% perturbation was suggested when the RPV cannot be specifically obtained.     

Economic estimates of feral swine damage and control in 11 US states

We report the results of one of the most comprehensive surveys on feral swine (Sus scrofa) damage and control in 11 US states (Alabama, Arkansas, California, Florida, Georgia, Louisiana, Mississippi, Missouri, North Carolina, South Carolina and Texas). The survey was distributed by the USDA National Agricultural Statistical Service in the summer of 2015 to a sample of producers of corn (Zea mays), soybeans (Glycine max), wheat (Triticum), rice (Oryza sativa), peanuts (Arachis hypogaea), and sorghum (Sorghum bicolor) in the 11-state region. Producers that failed to respond to the initial mailing received multiple follow-up phone calls in an attempt to minimize non-response bias, and a total of 4377 responses were obtained. Findings indicate that damage can be substantial. The highest yield loss estimates occur in peanut and corn production in the Southeast and Texas. Control efforts are common, and producers incur considerable costs from shooting and trapping efforts. Extrapolating crop damage estimates to the state-level in 10 states with reportable damage yields an estimated crop loss of $190 million. Though large, this number likely represents only a small fraction of the total damage by feral swine in the 10 states because it only includes crop damage to six crops. We hope findings from this survey will help guide control efforts and research, as well as serve as a benchmark against which the effectiveness of future control efforts can be measured.     

Effect of biogas digestate,animal manure and mineral fertilizer application on nitrogen flows in biogas feedstock production

The expansion of biogas feedstock cultivation may affect a number of ecosystem processes and ecosystem services, and temporal and spatial dimensions of its environmental impact are subject to a critical debate. However, there are hardly any comprehensive studies available on the impact of biogas feedstock production on the different components of nitrogen (N) balance. The objectives of the current study were (i) to investigate the short-term effects of crop substrate cultivation on the N flows in terms of a N balance and its components (N fertilization, N deposition, N leaching, NH₃ emission, N₂O emission, N recovery in harvested product) for different cropping systems, N fertilizer types and a wide range of N rate, and (ii) to quantify the N footprint of feedstock production in terms of potential N loss per unit of methane produced. In 2007/08 and 2008/09, two field experiments were conducted at two sites in Northern Germany differing in soil quality, where continuous maize (R1), maize–whole crop wheat followed by Italian ryegrass as a double crop (R2), and maize–grain wheat followed by mustard as a catch crop (R3) were grown on Site 1 (sandy loam), and R1 and a perennial ryegrass ley (R4) at Site 2 (sandy soil rich in organic matter). Crops were supplied with varying amounts of N (0–360 kg N ha⁻¹, ryegrass: 0–480 kg N ha⁻¹) supplied as biogas digestate, cattle slurry, pig slurry or calcium-ammonium nitrate (CAN).Mineral-N fertilization of maize-based rotations resulted in negative N balances at N input for maximum yield (Nopt), with R2 having slightly less negative balances than R1 and R3. In contrast, N balances were close to zero for cattle slurry or digestate treatments. Thus, trade-offs between substrate feedstock production and changes of soil organic matter stocks have to be taken into consideration when evaluating biogas production systems. Nitrogen losses were generally dominated by N leaching, whereas for the organically fertilized perennial ryegrass ley the ammonia emission accounted for the largest proportion. Nitrogen balance of the ryegrass ley at Nopt was close to zero (CAN) or highly positive (cattle slurry, digestate). Nitrogen footprint (NFP) was applied as an eco-efficiency measure of N-loss potential (difference of N input and N recovery) related to the unit methane produced. NFP ranged between −11 and +6 kg N per 1000 m³ methane at Nopt for maize-based rotations, without a significant impact of cropping system or N fertilizer type. However, for perennial ryegrass ley, NFP increased up to 65 kg N per 1000 m³. The loose relation between NFP and observed N losses suggests only limited suitability for NFP.     

Impact of Different Weed Types on Growth and Yield of Mungbean (Vigna radiata L. Wilczek)

The influence of different weed types (grass, broadleaved and sedge species) on growth and yield parameters of mungbean ( Vigna radiata L. Wilczek) was evaluated under field conditions. The presence of all types of weeks had the most significant effect on growth and yields of mungbean. Broadleaved species alone had a greater adverse effect than grasses, and the influence of sedges was the lowest. The adverse effect of weeds was most prominent on vegetative growth. The influence on yield components reduced with time. However, the adverse impact of weeds on yields was similar to that on vegetative growth. A significant correlation between weed biomass and yield loss was observed. The study indicated the critical competitive period to be in the vegetative phase. Some possible implications for selective weeding are presented.     

GROUND WATER QUALITY IN THE INDUS PLAINS OF PAKISTAN AND ITS USE FOR CROP PRODUCTION DURING RECLAMATION OF SALINE-SODIC SOILS

<正> The Indus Plains of Pakistan lies between 23°to 37°latitude and 61°to 76°longi-tude in the northern hemisphere. The total Canal Commanded Area (CCA) is about 13.50million hectares of which 11.21 million hectares are cultivated. At present, 103 millionacre-feet river flow is diverted into irrigation canals. In addition, 42 million acre feet of thegroundwater are being pumped through 257697 tubewells to supplement the canal supplies.     

农作物多目标育种综合选择方法研究初报

采用层次分析法和效用函数法相结合的多目标决策技术,对农作物多目标育种中亲本选择方法进行了初步探讨.以玉米为例,建立了多目标育种综合选择函数,对1990年华北春玉米区试品种的16个自交系进行了例证分析.结果表明,由综合选择函数值排序前6位自交系参于组配的新品种,区试产量均高于对照农大60,这充分说明了育种选择函数的有效性.该方法原理简单,计算容易,能够把育种学家的知识、经验与系统工程学的定量分析法有机结合,是选择指数、典型相关等多元统计方法所不及的新的作物育种选择方法,对提高作物育种的相对效果,具有重要的理论和实践意义.     

Loss of yield caused by soil erosion on sandy soils in the UK

Abstract. Soil productivity, the intrinsic ability of land to yield useful products, can be affected by soil erosion. While much research has been carried out on the processes, there is as yet little information on the impact of soil erosion on in situ productivity of agricultural land in the British Isles. This paper reports the results of a de-surfacing experiment on deep sandy soils in East Anglia. Grain yields of fertilized barley planted immediately after de-surfacing were at least 15 and 45% less on 15 and 25 cm de-surfaced plots than on non-desurfaced soils. There was strong evidence pointing to an acceleration of soil erosion itself on the de-surfaced plots. Both the amount of water stored in the topsoil and water use by the crop decreased with increasing severity of simulated erosion. We observed a drop in organic matter and readily available nitrogen with erosion. Nitrogen mineralization and leaching losses were also affected by simulated soil erosion. The experiment showed that sudden severe erosion may induce substantial barley production losses on deep sandy soils. The size and effect of de-surfacing depends on a number of factors such as soil depth, subsoil type, precipitation and crop type.     

Resource utilisation and economy of soil tillage in crop production systems

Resource use in crop production is analysed with reference to the concept of potential yield, based on the relationships between the balances of energy and mass in plant growth. Three models of the production process are proposed: a bio-physical model which looks at the conversion of energy and mass into a potential yield of biomass, a business model which assesses the economics of the conversion process and a feed-back model which points the way towards on-line optimisation. The impacts of environmental, nutritional and physiological constraints on potential yield are discussed. The business model emphasises the importance of scale of operation in reducing the costs of crop production by spreading the fixed costs of machinery. The contributions of additional energy inputs in the form of fertilisers, agrichemicals and machinery in improving the overall efficiency with which solar energy is converted into biomass, together with the pivotal role of nitrogenous fertiliser in increasing yields, are examined. Nitrogenous fertilisers underpin high yields and account for about half the energy supplied by the farmer to a cereal crop. Tillage helps in ameliorating the environmental constraints on crop growth. The implications of sustainability, and climate change, for resource use in crop production are discussed briefly.     

半干旱区农田水肥调控试验与作物生长模型

以农田水肥调控为依据，从农田生态学角度探讨了水分和养分最优配置问题，提出了叶面积积分、叶面积持续期的概念及计算公式，建立了作物个体和群体水平上的作物生长模型和有关统计模型，计算了最佳施肥量和最小耗水系数，从理论和实践上为高效和谐作物生长系统的建立提供了依据。     

夏玉米锌吸收特点的研究

通过测定夏玉米不同生育期各部位含锌量表明,三叶期至拔节期是吸收速率最快的时期,吸收量最大时期出现在大喇叭口至轧熟期。从全生育期看,前期后期吸收锌的绝对量很少,中期和中后期多。夏玉米对锌的吸收主要受干物质积累进程制约。锌的分配重点前期是叶片,此后逐渐向茎转移,到中后期营养器官的锌向雌穗集中。