Simulation of forage harvest and conservation on dairy farms

A computer model was developed to simulate forage systems on dairy farms. The model simulated alfalfa growth, corn silage and corn grain yields, harvest, storage, feeding and ration formulation for a dairy herd. A 26-year series of historical weather data from East Lansing, Michigan, was used to compare management and technological alternatives on the basis of average net return and year-to-year variations. For example, a four-cut alfalfa system was found to be more profitable than a three-cut system 90% of the time. The comparison of a hay system with a silage system was very sensitive to forage intake assumptions; the break-even point shifted from 120 ha to 40 ha when silage intake was increased by 5%. The model can be used to assess the impact of new forage conservation methods under a wide range of climatic and management conditions.     

Pasture and forage crop systems for non-irrigated dairy farms in southern Australia. 2. Inter-annual variation in forage supply,and business risk

Inter-annual climatic variability poses a substantial management and profitability challenge for pasture-based dairy producers in southern Australia. The effects of a range of seasonal scenarios on the production and profit of non-irrigated dairy farm systems using several different forage bases were investigated for two regions in southeast Australia using a systems modeling approach. For the Terang district, seasonal scenarios were constructed around combinations of early, average or late autumn rains, and short, average or long spring flushes. For the higher-rainfall Ellinbank district, scenarios were constructed around either above- or below-average summer–autumns or winter–springs.     

4LZJ-3自走式牧草籽粒收获机的推广应用

文章对4LZJ-3自走式牧草籽粒收获机推广情况、主要技术参数、组成结构、工作流程、性能特点等进行了阐述。该机具设计紧凑、操作方便、机动灵活,采用切流和轴流式双滚筒脱粒,风机转速为手动无级调速,杂余复脱二次清选,滚筒转速为有级变速,行走为四档无级变速。液压和电器系统设计完善,田间作业和远距离转移适应性强,可靠性高。     

Simulating differences in net returns from beef production under alternative forage systems and management practices

A biological simulation model and a linear programming model were interfaced to determine production efficiencies and the optimal carrying capacity of a cow-calf producer in East Texas and to compare net returns to the model farm, given alternative tame forage systems and management practices. Experimental data both on forage systems and on livestock were used to verify and validate the simulated herds. The results showed that (1) of the three tame forage systems analyzed, warm-season perennial forages provided a relatively higher carrying capacity/ha, whereas a mix of both warm- and cool-season forages that allows year-round grazing gave relatively higher net returns/ha to management; (2) nutritional stress during winter months decreased animal performance proportionately more than it decreased feed costs; and (3) although spring-calving herds included more animals than corresponding fall-calving herds on the same land area, fall-calving herds produced more liveweight sales and generally higher net returns.     

Pasture and forage crop systems for non-irrigated dairy farms in southern Australia: 3. Estimated economic value of additional home-grown feed

Dairy systems in southern Australia rely on grazed feed from pasture to supply between 50% and 70% of total herd feed requirements on an annual basis. However, the dominant pasture type in the region, which is based on perennial ryegrass (Lolium perenne), commonly results in feed deficits in summer which must be filled with supplements purchased off-farm, and feed surpluses in spring which must be conserved. Both of these strictures impose costs on farm businesses. It is likely, therefore, that additional grazeable feed available to dairy herds in southern Australia may have different economic value when interactions between season, stocking rate, calving date, and locality are taken into account. The analysis reported in this paper aimed to estimate, using the farm systems simulation model UDDER, the effect of these interactions on the efficiency with which extra feed can be converted to extra milk production, and therefore the possible gross economic value of the additional feed.‘Base’ farm simulations for ‘average’ and ‘top 10%’ farms (ranked according to farm profitability) in two localities (Terang: average annual rainfall 796 mm, 8 month growing season; and Ellinbank: average annual rainfall 1085 mm, 9-10 month growing season) were created to mimic the physical production and profitability of these farms as seen in regional farm benchmark datasets. These simulations were then altered to add the equivalent of 10% of the total annual herbage accumulation used in the Base simulation either on a pro-rata basis all year round, or in autumn only, in winter only, in spring only, or in summer only. The additional feed amounted to 620 and 780 kg DM/ha for Terang average and top 10% farms respectively, and 735 and 905 kg DM/ha for Ellinbank average and top 10% farms respectively. The management policies used in the Base simulations were then adjusted to harvest as much of the extra feed as possible, either by direct grazing or through silage conservation, while keeping the key system state indicators of cow condition score and average farm pasture cover within the limits known to result in long-term sustainable production.The efficiency with which extra feed was utilised was greatest in summer in all scenarios (80-100% of the extra feed supplied was harvested, all by direct grazing). This translated into consistently high gross economic returns of between $0.26 and $0.34 per kg DM of extra feed added to the model. Utilisation efficiency was lower in all other seasons and/or required marked increases in silage conservation, both of which resulted in lower gross economic returns per kg DM of additional feed. The impact of interactions between locality, season, stocking rate (higher in top 10% farm simulations than average farm simulations) and calving date (earlier at Terang than at Ellinbank) were clearly captured in the model. These interactions have very large effects on the profitability of growing extra feed at different times of the year. Agronomic research for the southern Australia dairy industry should focus on low-cost ways for supplying additional grazeable feed in summer, since current forage species options for this time of year are limited.     

Life cycle assessment of greenhouse gas emissions from beef production in western Canada: A case study

A life cycle assessment (LCA) was conducted to estimate whole-farm greenhouse gas (GHG) emissions from beef production in western Canada. The aim was to determine the relative contributions of the cow-calf and feedlot components to these emissions, and to examine the proportion of whole-farm emissions attributable to enteric methane (CH₄). The simulated farm consisted of a beef production operation comprised of 120 cows, four bulls, and their progeny, with the progeny fattened in a feedlot. The farm also included cropland and native prairie pasture for grazing to supply the feed for the animals. The LCA was conducted over 8 years to fully account for the lifetime GHG emissions from the cows, bulls and progeny, as well as the beef marketed from cull cows, cull bulls, and progeny raised for market. The emissions were estimated using Holos, a whole-farm model developed by Agriculture and Agri-Food Canada. Holos is an empirical model, with a yearly time-step, based on the Intergovernmental Panel on Climate Change methodology, modified for Canadian conditions and farm scale. The model considers all significant CH₄, N₂O, and CO₂ emissions and removals on the farm, as well as emissions from manufacture of inputs (fertilizer, herbicides) and off-farm emissions of N₂O derived from nitrogen applied on the farm. The LCA estimated the GHG intensity of beef production in this system at 22 kg CO₂ equivalent (kg carcass)⁻¹. Enteric CH₄ was the largest contributing source of GHG accounting for 63% of total emissions. Nitrous oxide from soil and manure accounted for a further 27% of the total emissions, while CH₄ emissions from manure and CO₂ energy emissions were minor contributors. Within the beef production cycle, the cow-calf system accounted for about 80% of total GHG emissions and the feedlot system for only 20%. About 84% of enteric CH₄ was from the cow-calf herd, mostly from mature cows. It follows that mitigation practices to reduce GHG emissions from beef production should focus on reducing enteric CH₄ production from mature beef cows. However, mitigation approaches must also recognize that the cow-calf production system also has many ancillary environmental benefits, allowing use of grazing and forage lands that can preserve soil carbon reserves and provide other ecosystems services.     

Pasture and forage crop systems for non-irrigated dairy farms in southern Australia. 1. Physical production and economic performance

The dairy industry in southern Australia relies on perennial ryegrass pasture to supply 60–70% of the diet of lactating cows. Improvements in the amount and quality of home-grown forage used for dairy cow feeding are critical for further productivity gains in the industry. A modeling approach was used to estimate the effects of changing the forage system on farm business profit. Base models (using 100% of farm area in perennial ryegrass pasture) were constructed for above-average (Top 40%) and high performing (Top 10%) farm types typical of two locations: Terang in southwest Victoria and Ellinbank in Gippsland, eastern Victoria. These models were then re-simulated using different forage base options such as: oversowing annual ryegrass, winter crops (annual ryegrass monoculture, winter cereal grown for whole crop silage), summer crops (grazing brassicas, maize), combinations of these (double cropping), or summer shoulder pasture (notionally based on tall fescue) on between 10% and 100% of farm area.     

The yield,quality and profitability of annual forage,perennial pasture and perennial forage systems under irrigation

Intensive fodder production systems were compared under irrigation in western New South Wales. The three basic systems studied were:

• 1.(1) Annual forages (Sorghum bicolor × S. sudanense plus Avena sativa).
• 2.(2) Perennial pasture (Paspalum dilatatum).
• 3.(3) Perennial forage (Medicago sativa).

The first two systems included nitrogen fertilizer or legume options, while the last had the option of including a perennial sorghum.Dry matter production was highest in the annual forage system (maximum of 30·5 tonnes ha⁻¹ year⁻¹), although annual establishment costs were higher than for perennial systems. The perennial pasture yielded 21·5 tonnes ha⁻¹ year⁻¹ but, like the annual forage system, 250 kg N ha⁻¹ year⁻¹ was required to obtain this yield. The perennial forage yielded 19·8 tonnes ha⁻¹ year⁻¹ without nitrogen fertilizer. Furthermore, it yielded more digestible dry matter and nitrogen than any other system.Although the annual forage system was the most profitable when based upon a set price for hay, the best system for grazing was difficult to determine; factors relating to grazing management are discussed.     

A short-term mechanistic model of forage and livestock in the semi-arid Succulent Karoo: 1. Description of the model and sensitivity analyses

This series of two papers describes a mechanistic model that simulates within years the productivity of vegetation and livestock on the communal semi-arid rangeland of the Succulent Karoo of South Africa. The model enables users to evaluate short-term management decisions on the production of milk and meat and to develop sets of equations and rules for long-term models designed to examine the effects of different strategies on the sustainability of the ecosystem.A soil moisture module partitions daily rainfall between runoff, infiltration and drainage and also simulates the loss of soil moisture by evaporation and transpiration. Forage production by different types of plant is modelled in relation to soil moisture and the present potential for growth. Three factors are assumed to influence the animal’s preference for a specific type of plant or part of a plant: relative abundance, ease of harvesting and digestibility. The model combines three mechanisms of food intake regulation: the rate at which the animal is able to eat forage, physical capacity of the digestive system, and, in young animals, their growth potential. Metabolisable energy intake is partitioned between maintenance, accretion/depletion of body protein and fat, conceptus growth and milk production. Reproductive and survival rates are simulated in relation to predicted liveweight and liveweight changes for the different age classes of livestock.     

联合收割机与运粮车协同作业调度技术研究

针对联合收割机作业路径规划不合理、联合收割机与运粮车无法协同优化调度等问题,以最小化联合收割机总非生产性作业时间和非生产性作业等待时间为目标,构建多机型多任务协同优化调度模型,设计多机协同优化调度算法(MMCOSA)。首先通过对传统蚁群算法(ACO)进行改进,计算得到联合收割机的静态路径规划方案,然后采用相对距离最近策略实现联合收割机与运粮车协同作业动态优化。试验结果表明,采用MMCOSA算法计算得到的联合收割机总非产性作业时间和非生产性作业等待时间均比传统ACO算法的结果平均缩短17.5%和19.02%,MMCOSA算法不仅加快收敛速度,而且缩短作业时间,为农忙时节联合收割机与运粮车的协同调度问题提供有效的解决方案。     

Economics of feeding corn silage versus corn grain to beef steers as affected by interest rates,liquidity preference and opportunity cost of capital

This study uses a linear programming (LP) model to incorporate interest rates, liquidity preference and opportunity cost of capital into a decision making process for a beef producer. It is concluded that interest rates significantly affect the returns to labour and management, but, even when liquidity preferences and opportunity cost of capital are considered, extremely high interest rates would be required before it would be more economical to feed a high corn grain ration versus a high corn silage ration.     

BANAD: A farm model for ex ante assessment of agro-ecological innovations and its application to banana farms in Guadeloupe

The ex ante assessment of innovative agro-ecological innovations is a key step in the development of more sustainable crop management systems. To this end, models are useful tools because they make it possible to rapidly assess numerous innovations in different contexts. Whereas many farm optimisation models focusing on the farmer’s strategic decision to adopt new crop management systems have been published, little attention has been given to the ex ante modelling of the dynamic operational impacts of innovation adoption at the farm level. BANAD, a mechanistic model for such applications, is proposed. It allows the ex ante assessment of innovative management systems including new agro-ecological techniques, while taking into account different farming contexts and policy and market conditions. It includes three components: (i) a crop management system model, (ii) a crop model (SIMBA) and (iii) a farming system model. Our results applied to the ex ante assessment of six innovative banana management systems for three contrasted farm types in Guadeloupe showed that the impacts of agro-ecological innovations, which include rotations, improved fallow, intercropping, pest-resistant cultivar, and an integrated organic system, can vary considerably according to (i) the farm type in which the innovation is integrated, (ii) the nature of the agro-ecological innovations, and (iii) the criteria considered and the temporal horizon of the assessment. Innovative intercropping systems that were effective at the field level in terms of the yield improvement and decreased pesticide use could be problematic at the farm level because they increased the workload and decreased income. The adoption of rotations or improved fallow seemed to be relevant for smallholders but could induce a critical period of 1.5-2.5 years during which income decreased drastically. Under certain conditions of markets and subsidies, very environmentally friendly innovations that are less productive can however be economically effective.     

A general cattle production systems model. I: Structure of the model

A deterministic model for simulating beef cattle production under a wide range of management schemes and environments with cattle differing widely in genotypes for size, growth and milk production is described. In the model, genotypes are specified as production potentials, which are reached only if past and present planes of nutrition are adequate. Intake of forage and/or other feed is simulated as a function of the size and physiological status of the animals and the availability, digestibility and crude protein content of the feed. Animal performance is calculated from the nutrient intake and the animals' condition (fatness), degree of maturity and genetic potential. The model has been used for simulating beef cattle production under several widely differing sets of environmental and management conditions in Guyana, Colombia, Venezuela, Botswana, Texas and Mid-western United States and for simulating dairy-beef production systems in Colombia, Tanzania and Botswana. Results of simulations of existing conditions have coincided rather closely with actual production levels.     

Incorporation of environment and feed quality into a net energy model for beef cattle

The California net energy system has gained wide acceptance as a method for predicting rates of gain in growing and finishing beef animals. Researchers at the University of Kentucky, in co-operation with agricultural scientists in two regional research projects, NC-114 and S-156, have developed an interactive model that enhances the usefulness of the net energy system by including skeletal size, feed quality, temperature and relative humidity to determine feed intake and utilisation. Basically, the intake based on feed availability, nutrient composition, potential skeletal size and heat loss potential. After the feed is consumed, it is utilised according to the productive status of the animal, i.e. growth, lactation, foetal development, etc., using a modified form of the net energy system to predict weight change.The model allows a researcher to easily modify environment, feed, breed characteristics and productive status so as to evaluate their influence on the performance of the animal.     

基于时间序列模型的黑龙江省粮食水足迹分析与预测

利用CROPWAT 8.0 模型计算了2000-2017年黑龙江省主要粮食作物水足迹,并利用自回归移动平均模型ARIMA对2018-2022年黑龙江省粮食作物水足迹进行了预测.黑龙江省粮食作物生产水足迹增长迅速,2000-2017年黑龙江省粮食作物生产水足迹总量增长了2.84倍;玉米的水足迹为0.47~1.07 m³/kg,而大豆、小麦和水稻的水足迹分别为1.35~2.39,1.12~2.99和1.76~1.41 m³/kg;小麦的绿水足迹占比最高,约为72.74%,其次是玉米(66.26%)和大豆(64.59%),而水稻的绿水足迹占比最低,约为46.99%;4种作物的灰水占水足迹的比例均低于1.12%.ARIMA模型预测结果表明,黑龙江省粮食作物的水足迹将逐年升高,玉米的水足迹呈逐年下降趋势,水稻和大豆的水足迹呈逐年上升趋势,小麦的水足迹基本不变.考虑到黑龙江水资源相对缺乏,而粮食作物水足迹总量逐年上升,建议加强农业管理,提高作物的水分利用效率.     

晋西黄土区人工刺槐林植被结构分析

山西吉县蔡家川流域,在九十年代进行了大面积的人工造林,其中阔叶林主要是刺槐林及刺槐与侧柏的混交林,研究其植被结构对以后人工林的营造和抚育有重要意义。分坡向、坡度和混交类型,选择了不同类型的24块标准地,测定各标准地内乔木的树高、胸径、冠幅和枝下高,利用二元材积表,计算样地的立木材积量,同时测出草本层的生物量和枯落物层的生物量。通过比较草本层、枯落物层的生物量和乔木层的材积量,由此确定在不同的立地类型内种植何种混交林最佳。     

Energy consumption, greenhouse gas emissions and economic performance assessments in French Charolais suckler cattle farms: Model-based analysis and forecasts

The environmental and economic performance of five Charolais beef production systems (three specialized beef producer test cases in grassland areas and two mixed crop-livestock test cases with a more intensive production system) were assessed by coupling an economic optimization model (“Opt’INRA”) with a model assessing non-renewable energy (NRE) consumption and greenhouse gas emissions (“PLANETE”). The test cases studied covered a relatively diverse range of raised and sold animals: calf-to-weanling or calf-to-beef systems (animals sold: from 10-month-old weaners to 36-month-old beef steers). In 2006, NRE consumption ranged from 26,440 to 31,863 MJ/ton of live weight produced over 1 year. Fuels and lubricants were the main factors of NRE consumption, followed by fertilizers and farm equipment. Livestock was the main driver of global warming potential. GHG emissions, at 14.3-18.3 tCO₂eq/t LW, were mainly determined by the proportion of cows in the total herd livestock units, according to the farming system deployed, i.e. calf-to-weanling vs. calf-to-beef. Against a background of rising energy costs, farms running mixed crop-livestock systems enjoy greater flexibility to adjust their farming systems than grassland-based farms, enabling them to minimize the drop in income over the timeframe to 2012 (−3%). In this same setting, specialist beef producers face a 15-25% drop in income. In all the scenarios run, system adjustments designed to minimize the drop in income have only a very limited impact on NRE consumption and GHG emissions.     

Development of DRAIN-WARMF model to simulate flow and nitrogen transport in a tile-drained agricultural watershed in Eastern Canada

A new watershed model, DRAIN-WARMF, was developed to simulate the hydrologic processes and the nitrogen fate and transport that occur in small, predominantly subsurface-drained, agricultural watersheds that experience periodic freezing and thawing conditions. In this modeling approach, surface flow is simulated using a watershed scale model, WARMF, and subsurface flow is estimated using a field-scale model for subsurface-drained shallow water table fields, DRAINMOD 5.1. For subsurface flow calculations, the watershed is subdivided into uniform cells, and DRAINMOD is run on each cell with inputs based on the individual hydrologic characteristics of the cell. The coupling results in a distributed parameter model that calculates the total flow at the outlet of a watershed as well as the nitrogen losses. The model was evaluated for the St. Esprit watershed, located approximately 50 km northeast of Montreal. Simulations were carried out from 1994 to 1996; data from 1994 and 1995 was used for model calibration and data from 1996 was used for model validation. The new model was able to adequately simulate the hydrologic response and nitrate losses at the outlet of the watershed. Comparing the observed daily flow/monthly nitrogen with the model's outputs over the validation period returned an R² value of 0.74/0.86 and modeling efficiency of 0.72/0.83. This clearly demonstrates the model's ability to simulate hydrology and nitrogen losses occurring in small agricultural watersheds in cold climates.     

Competitiveness of beef farming in Rio Grande do Sul State, Brazil

The aim of this study was to typify competitiveness on beef cattle farms from the western border region of the state of Rio Grande do Sul, Brazil. Sixty-three farmers, each with an individual farm area exceeding 900 ha, were interviewed using a semi-structured questionnaire, divided in four sections: technology (TEC), management (MAN), market relationships (MR) and institutional environment (IE). Data were analysed using Cluster and Discriminant analyses. Beef cattle producers were divided into three levels of competitiveness: low (LCL), medium (MCL) and high (HCL). Comparing LCL × MCL, the former group of farmers showed lower levels of pasture and reproduction management than the latter (subfactors within TEC). When LCL × HCL were compared, the main differences were the lower access to technological innovation and low investment with herd genetics of LCL compared with HCL. The lower level of management activities (performance recording, animal handling and calculation of financial parameters) of MCL compared with HCL were the main variables that differ between these farms. Cattle producers interviewed here were, in general, competitive, mainly due to the use of technologies on farm. However, there were limitations in the variables related to management.