Greenhouse gas emissions from the Canadian beef industry

Commodity-specific estimates of the greenhouse gas (GHG) emissions from Canadian agriculture are required in order to identify the most efficient GHG mitigation measures. In this paper, the methodology from the Intergovernmental Panel on Climate Change (IPCC) for estimating bovine GHG emissions, for census years from 1981 to 2001, was applied to the Canadian beef industry. This analysis, which is based on several adaptations of IPCC methodology already done for the Canadian dairy industry, includes the concept of a beef crop complex, the land base that feeds the beef population, and the use of recommendations for livestock feed rations and fertilizer application rates to down-scale the national area totals of each crop, regardless of the use of that crop, to the feed requirements of the Canada’s beef population. It shows how high energy feeds are reducing enteric methane emissions by displacing high roughage diets. It also calculates an emissions intensity indicator based on the total weight of live beef cattle destined for market. While total GHG from Canadian beef production have increased from 25 to 32 Tg of CO₂ equiv. between 1981 and 2001, this increase was mainly driven by expansion of the Canadian cattle industry. The emission intensity indicator showed that between 1981 and 2001, the Canadian beef industry GHG emissions per kg of live animal weight produced for market decreased from 16.4 to 10.4 kg of CO₂ equiv.     

水产饲料含水率预测模型研究

目前饲料烘干技术上最大的难点在于缺乏有效的干燥数学模型来准确预测饲料的含水率,为此,文章基于指数函数建立三种水产饲料的含水率预测数学模型,并进行试验验证.首先在循环风机频率为30 Hz,料层厚度为30 mm的条件下,对三种水产饲料进行单一温度(90℃、105℃、120℃、135℃)烘干试验,其次基于单一温度试验数据,采...     

Dairy farm nutrient management model. 1. Model description and validation

Intensive dairy farming results in significant phosphorus (P) emission to the environment. Field data indicates that farm-gate P surplus is highly positive in Finland and strategies to mitigate the surplus are needed. The objectives of this study were to build a P cycle model for dairy farms (1) and to validate the model with independent field data (2). The dairy farm nutrient management model (“Lypsikki”) described in this paper includes three sub-models: (1) soil and crop, (2) dairy herd and (3) manure management. The model is based on empirical regression equations allowing estimations of crop and milk yields in response to increased fertilisation and nutrient supply, respectively. In addition, the model includes a dynamic simulation model of the dairy herd structure and calculation of the farm-gate nutrient surplus. The model was validated with independent annual (average for 1-4 years) farm-gate P surplus data from 21 dairy farms. Model simulations were conducted using two levels of soil productivity, mean (M) and low (L). The model validation indicated a strong relationships between model-predicted and observed farm-gate P surplus: (M: R² = 0.77 and L: R² = 0.80). The line bias between the model-predicted and observed data was negligible and insignificant (P > 0.6) suggesting a robustness of the model. The mean biases were relatively high and significant (M: 4.7 and L: 1.8 kg/ha, P < 0.001), but evidently related to overestimation of crop yields that has to be taken into account when using the model on a single farm. The prediction error of the model (observed minus predicted P surplus) was significantly correlated to the difference between simulated and observed P import in feeds (M: R² = 0.55 and L: R² = 0.51). This suggests either that all the dairy farms did not fully exploit the possibilities in the crop production or that all the model assumptions are not correct. The effects of purchased feed and fertiliser P and exported milk P (per cow or cropping area) on farm-gate P surplus were of the same magnitude in both observed and simulated data. This implies that the model developed can be used as a management decision tool to find strategies to mitigate P surplus on dairy farms.     

Poultry production for the urban market in developing countries: The case of Zaire

The profitability of establishing commercial poultry enterprises supplying the main urban markets in Zaire was evaluated in this study. In 1982 data were collected from eight layer farms, ranging in size from 80 to 150 000 layers per production period, located in Bas-Zaire and areas surrounding Kinshasa, Zaire. In addition, data were also collected from three farms that produced broilers as well as eggs. These poultry enterprises were analyzed, based upon their current level of production capacity, input costs and annual net returns.The results indicate that the profitability of layer farms appeared to be influenced by the rate of mortality, the rate of laying and the high cost of imported supplies such as hatching eggs, baby chicks, medications, vitamins, minerals and protein feeds. A low-cost poultry feed ration that met the requirements for both broilers and layers was developed using mainly Zairian ingredients. Access to lower cost medical supplies, better management practices and cheaper feeds appeared to be the key to expanding commercial poultry enterprises in Zaire and other developing countries.     

The economic value of glyphosate-resistant canola in the management of two widespread crop weeds in a Western Australian farming system

Nitrogen fertilisation is a source of potential groundwater pollution and is a key issue in the current debate about the environmental impacts of agricultural production. It is also a key element in the management of cropping systems by farmers. Therefore, cropping system design entails the understanding and evaluation of farmers' fertilisation practices. Biophysical models describing the soil–plant system can serve this purpose. A comparison between model outputs and farmers' practices was made of a set of 128 apple (Malus domestica Borkh.) plots from 31 members of a farmers' co-operative in south-eastern France. Farmers' fertilisation practices were compared with theoretical practices generated by a series of soil–plant system models of increasing complexity, each model giving the amount of nitrogen that should be applied to the plot according to the knowledge included in the model. The model that reproduced farmers' fertilisation practices most closely was the most complex, taking all plant requirements, soil organic matter and residue mineralisation, denitrification and irrigation supply into account. A Monte Carlo method showed that the differences between farmers' practices and model outputs were not random. Spatial analysis showed a strong spatial organisation of these differences, mainly due to three farms. This congruence between farmers' practices and model outputs suggests the existence of some indicators that depict the N nutrition status of the orchard as a basis for rules indicating how much nitrogen should be applied. The spatial analysis suggests the existence of farmer and neighbourhood effects, which need to be explained. Models appear to be useful tools to study farmers' practices by removing biophysical effects (soil, variety, etc.). This raises new questions concerning agricultural research at the interface between the biophysical and social sciences.     

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.     

Feed resources,livestock production and soil carbon dynamics in Teghane,Northern Highlands of Ethiopia

In the Northern Highlands of Ethiopia, integrated crop-livestock production within smallholder farms is the dominant form of agricultural production. Feed availability and quality are serious constraints to livestock production in Ethiopia in general, and in its Northern Highlands in particular. The objective of this study was to describe the relationship between feed availability and quality and live weight gain, milk and manure production and the soil C balance in Teghane, Northern Highlands of Ethiopia. The so-called JAVA model procedure, that essentially predicts metabolizable energy intake and animal production on the basis of feed quality and quantity, has been used and linked to a soil carbon balance. Forages were ranked according to their quality (on the basis of metabolizable energy intake by livestock) in descending order. Rations were formulated by stepwise including components of increasingly lower quality to calculate the trade-offs between feed quantity and quality. In the model, the soil C balance was described in relation to soil organic matter decomposition, C input from roots, grazing and/or harvesting losses, feed residues and manure. Moreover, an analysis of monetary values of live weight gain/loss, manure and draught power is included. The results of the model showed that mean daily live weight gain and milk production per TLU continuously increased with decreasing herd size, while total annual live weight gain reached a maximum (62 Mg) at the use of the 30% best feeds and a herd size of 630 TLU. Soil C balance at this level of feed use is negative and deteriorates with increasing feed use. The model estimated an optimum herd size of 926 TLU to attain the maximum combined monetary value of live weight gain, manure and draught power at 50% feed use. Actual herd size in the study area was 1506 TLU. Our results indicate that in areas where feeds of very different quality are available, maximum benefits from meat and/or milk production and soil C balance can be attained by selective utilization of the best quality feeds, through a storage and carry-over system.     

Multicriteria fractional model for feed formulation: economic,nutritional and environmental criteria

The traditionally used linear programming model for feed formulation has sought the least-cost combination of ingredients that satisfies a specific level of nutritional requirements. Together with the search for the lowest possible cost, other aspects such as maximising diet efficiency in relation to proposed production objectives and minimising any excess that may lead to unacceptable damage to the environment, are other factors that are gaining in importance in the world of animal nutrition. Taking into account all these factors forces us not only to bear in mind the individual concentrations of each of the nutrients in the feed but also the ratios of these with other nutrients.In this work we show how a multi-objective fractional programming model is better adapted to current needs in feed design than the traditionally used least cost linear model. We also show how the model can be solved using the interactive multi-goal programming method with existing linear optimisation software.     

A model for recycling of feed nutrients in a crop,animal and biogas system in India

In northern India, with triple cropping intensity of fodder crops and recycling of feed nutrients in a milch animals and biogas system, from 1 ha of land it is possible to produce 82·63 GJ of energy and 906·11 kg of protein from milk; 263·93 kg of N; 148·93 kg of P₂O₅ and 90·94 kg of K₂O fertilizer from biogas slurry and 2897 kilowatts of power per annum for farm operation from biogas using the Kirloskar biogas engine. Traditional systems of wheat and rice cultivation can produce 93·87 GJ of energy and 654·25 kg of protein from food grain per hectare per annum. The recycling of feed nutrients in the available straws of rice and wheat crop can yield an additional 16·31 GJ of energy and 166·97 kg of protein from milk; 81·23 kg of N; 56·00 kg of P₂O₅ and 25·14 kg of K₂O fertilizer from biogas slurry and 1097 kilowatts of power per hectare annually from biogas.     

Ex ante analysis of new technology: A comparison of cassava for the feed and fresh markets in Colombia

This paper estimates the expected economic benefits of investment in two alternative research programmes to improve yields of cassava in Colombia. The benefits from an industrial cassava variety for the animal feed market are compared with those from a higher quality cassava suitable for the fresh food market. A linear programming least-cost feed mix model is used to calculate the cost reduction is poultry feed due to new cassava technology. The impact of this cost reduction is traced through single equation models of poultry supply and demand in order to estimate social benefits in an ex ante consumer surplus framework. Costs of the alternative research programmes are projected and internal rates of return are calculated.     

Dairy farm nutrient management model: 2. Evaluation of different strategies to mitigate phosphorus surplus

To reduce (P) surpluses on dairy farms and thereby the risk of P losses to natural waters we studied different management alternatives by a nutrient balance model described in the companion paper. The strategies evaluated mitigating the P surpluses were: mineral P fertilisation, dietary mineral P supplementation, replacement rate, animal density, production level, feeding intensity, dietary P concentration and nutrient efficiency in crop production. Responses to several interventions (e.g. mineral P fertilisation, purchased feed P, replacement rate) were similar to those observed in Finnish field studies. Reducing or completely giving up the use of purchased mineral P fertilisers was the most efficient measure to reduce P surplus. The slope between the amount of mineral fertilisers and P surplus was 0.98-0.99 (in the field data 1.0). Increased animal density resulted in a greater P surplus, but the slope between P input from purchased feed and surplus was considerably smaller (0.65) than that of P fertilisation. Increasing milk yield with improved genetic potential of the cows would have minimal effects on P surplus per unit of product, but it would increase P surplus per hectare. When the intensity of energy and protein feeding was increased, P surplus rose markedly both per unit of product and hectare. This is (1) due to increased dietary P concentration and (2) due to smaller marginal production responses than those calculated from feeding standards. Reducing dietary P concentration by constraining P excess per kg milk in least-cost ration formulation improved P efficiency in milk production and dairy farming system. However, feed cost increased as low P energy (sugar-beet pulp) and protein (soybean meal) supplements are more expensive than cereal grains or rapeseed feeds. Improving the nutrient use efficiency in crop production had a strong influence in the whole-farm efficiency and P surplus. The modelling results showed that Finnish dairy farms have a great potential to improve P efficiency and reduce P losses to the environment, even by increasing production intensity (milk/ha). It is concluded that the most cost-effective scenario to mitigate P surpluses at a dairy farm would be to reduce or give up the use of mineral P as fertilisers and supplements, and to improve the use of present soil P reserves.     

The life cycle impacts of feed for modern grow-finish Northern Great Plains US swine production

A life cycle assessment (LCA) model was developed to analyze the environmental impacts per head of swine for typical feed rations of Northern Great Plains (NGP) US grow-finish swine production. The all-inclusive ‘field to gate’ approach incorporated steps ranging from corn and soybean production to shipping the market weight pig to a slaughtering facility. Feed production scenarios included: (1) a standard feed diet of 72% corn and 28% soymeal using 100% synthetic fertilizer; (2) standard feed diet using 40% manure as fertilizer; (3) modified feed diet using dry distillers gains with solubles (DDGS), with 100% DDGS allocation towards ethanol production; and (4) modified feed diet with 50% DDGS allocation towards ethanol production. For the standard NGP feed diet, enteric emissions and feed production were the two largest contributors towards climate change impacts, while feed production further resulted in significant contributions towards human health damage (44.6%), ecosystem diversity (67.4%), and resource availability (75.0%). DDGS incorporation assuming 100% allocation reduced corn and soymeal inputs considerably, resulting in overall decrease in impacts associated with climate change (−2.7%), terrestrial acidification (−7.1%), and both marine (−14.6%) and freshwater eutrophication (−22.7%); however terrestrial ecotoxicity increased (+22.9%) due to natural gas drying. 50% DDGS allocation increased all impact categories, with the greatest change found for terrestrial ecotoxicity (48.4%). The study results highlight the significant LCA impact contributions associated with feed during grow-finish swine production, and the benefits associated with DDGS incorporation; however, LCA benefits were realized only if 100% DDGS allocation was applied towards ethanol production.     

Crop response of drought-tolerant and conventional maize hybrids in a semiarid environment

In the High Plains, corn (Zea mays L.) is an important commodity for livestock feed. However, limited water resources and drought conditions continue to hinder corn production. Drought-tolerant (DT) corn hybrids could help maintain high yields under water-limited conditions, though consistent response of such hybrids is unverified. In this two-year study, the effects of three irrigation treatments were investigated for a DT and conventional maize hybrid, Pioneer AQUAMax P0876HR and Pioneer 33Y75, respectively. In 2013, the drier of the 2 years, irrigation amounts and crop water use (ET_c) were greater for the conventional hybrid, but grain water use efficiency (WUE) and harvest index were significantly greater for the DT hybrid. In 2014, grain yields and WUE were not significantly different between hybrids. However, irrigation amounts, ET_c and biomass yields were greater for the conventional hybrid. Results from both years indicate that the DT hybrid required less water to maximize grain yield as compared to the conventional hybrid. Producing relatively high yields with reduced amounts of water may provide a means for producers to continue corn production in a semiarid environment with declining water supplies.     

Variation in reference crop evapotranspiration caused by the Ångström-Prescott coefficient: Locally calibrated versus the FAO recommended

Accurate estimation of the reference crop evapotranspiration (ET₀) is investigated due to its critical role in affecting calculation of crop water use and efficiency in agricultural ecosystems. The main emphasis in this paper is to clarify the possible uncertainty in the estimation of ET₀ associated with using un-calibrated Ångström-Prescott (A-P) coefficients. We first calibrated the coefficients using long-term data records from 34 sites in the Yellow River basin in China, and then applied these coefficients to estimate short wave irradiance (R_s) and ET₀ at 16 sites to evaluate the difference in ET₀ between the FAO recommended and the locally calibrated. We found that the direct use of the FAO recommended coefficients significantly affected the estimation of ET₀ at most sites, which differed from −3% to 15% at daily scale and from −4% to 16% at monthly scale from the locally calibrated ones. These differences are comparable with or larger than those caused by some alternatives of the FAO recommended algorithms for net irradiance or vapor pressure, which further highlights the importance of using the locally calibrated coefficients. The degree of difference in ET₀ showed a significant threshold relation with altitude and longitude in such a way that relatively small impact lies around 2233 m and 98°E, and away from these, the effect begins to increase. Given the large overestimation in water use as a consequence of the significant overestimation in ET₀ associated with the direct use of the FAO coefficients, especially in those high yield production areas with altitude <1200 m, we developed several relationships between the A-P coefficient a, b, (a + b) and other easily obtainable factors (altitude, longitude and air temperature). A three-step procedure was recommended in applying these relations, which was (1) determine if calibration is needed or not for a given location; (2) estimate one of the A-P coefficients, either a or b if calibration is needed; (3) estimate the remaining coefficient using relations of (a + b) due to its higher coefficient of determination. In summary, we have revealed the errors and areas that are most affected when using the un-calibrated coefficients, and discussed the consequence of such error on agricultural production, and proposed practical solutions to avoid large errors. These results are intended to make the research community aware of such errors so that more appropriate choice of these coefficients is made. We hope that similar assessment will be done in other climates, contributing to managing water resources efficiently in water basins.     

Differences in water use efficiency among annual forages used by the dairy industry under optimum and deficit irrigation

The increasing cost and scarcity of water for irrigation is placing pressure on Australian dairy farmers to utilize water more efficiently, and as result, water use efficiency (WUE) of forages is becoming an important criterion for sustainable dairy production. This study was conducted to identify more water use efficient forage species than the dominant dairy forage, perennial ryegrass (Lolium perenne L.). Seventeen annual forage species were investigated under optimum irrigation (I1) and two deficit irrigation treatments (nominally 66 and 33% of irrigation water applied to the optimal level), over 3 years at Camden, NSW, on a brown Dermsol in a warm temperate climate. Forages with the highest yield generally had the highest WUE_t (total yield/evapotranspiration). Under optimal irrigation, there was a three-fold difference in mean annual WUE_t between forages, with maize (Zea mays L.) having the highest (42.9 kg ha⁻¹ mm⁻¹) and cowpea (Vigna unguiculata (L.) Walp.) the lowest (13.5 kg ha⁻¹ mm⁻¹), with 11 of the forage species having a greater WUE_t than perennial ryegrass. The ‘harvested’ forages maize, wheat, triticale (Triticosecale rimpaui Wittm.) and maple pea (Pisum sativium L.) generally had higher mean WUE_t (26.7-42.9 kg ha⁻¹ mm⁻¹) than the remaining forages which were defoliated multiple times to simulate grazing (13.5-30.1 kg ha⁻¹ mm⁻¹). The reduction in annual WUE_t in response to deficit irrigation was greatest for the warm season forages with up to 30% reduction for maize, while most of the cool season annuals were not significantly affected by deficit irrigation at the levels imposed. In order to maximize WUE_t of any forage, it is necessary to maximize yield, as there is a strong positive relationship between yield and WUE_t. However, while WUE_t is an important criterion for choosing dairy forages, it is only one factor in a complex system. Choice of forages must be considered on a whole farm basis and include consideration of yield, nutritive value, cost of production and risk.     

Development and evaluation of integrated water and nitrogen model for maize

Maize (Zea mays L.) is an important food crop for irrigated regions in the world. Its growth and production may be estimated by different crop models in which various relationships between growth and environmental parameters are used. For simulation of maize growth and grain yield, a simulation model was developed (Maize Simulation Model, MSM). Dynamic flow of water, nitrogen (N) movement, and heat flow through the soil were simulated in unsteady state conditions by numerical analysis in soil depth of 0–1.8 m. Hourly potential evapotranspiration [ET_p(t)] for maize field was estimated directly by Penman–Monteith method. Hourly potential evaporation [E_p(t)] was estimated based on ET_p(t) and canopy shadow projection. Actual evaporation of soil surface was estimated based on its potential value, relative humidity of air, water pressure head and temperature at soil surface layer. Actual transpiration (T_a(t)) was estimated based on soil water content and root distribution at each soil layer. Hourly N uptake by plant was simulated by N mass flow and diffusion processes. Hourly top dry matter production (HDMA^j + 1, where j is number of hours after planting) was estimated by hourly corrected intercepted radiation (RSLT^j + 1) by plant leaves [determined from leaf area index (LAI^j + 1)] with air temperature, the maximum and minimum plant top N concentration and the amounts of nitrogen uptake. The value of LAI^j + 1 at each hour was estimated by the accumulated top dry matter production at previous hour using an empirical equation. Maize grain yield was estimated by a relationship between harvest index and seasonal plant top dry matter production. The model was calibrated using data obtained under field conditions by a line source sprinkler irrigation. When the values of water and nitrogen application were optimum, grain yield (moisture content of 15.5%) was 16.2 Mg ha⁻¹. Model was validated using two independent experimental data obtained from other experiments in the Badjgah (Fars province). The experimental results validated the proposed simulation model fairly well.     

Optimal coupling combinations between irrigation frequency and rate for drip-irrigated maize grown on sandy soil

This study was conducted over 2 years (2007 and 2008) to establish the optimal combinations between irrigation frequency and rate for drip-irrigated maize using water production functions and water use-yield relationships. A field experiment was conducted using a randomized complete block split plot design with four irrigation frequencies (F₁, F₂, F₃ and F₄, irrigation events once every 1, 2, 3 or 4 days, respectively) and three drip irrigation rates (I₁: 1.00, I₂: 0.80, and I₃: 0.60 of the estimated evapotranspiration, ET) as the main and split plots, respectively. Our results show that yield variables and water use efficiencies (WUEs) increased with increasing irrigation frequency and rate, with non-significant differences between F₁ and F₂ in yield variables and between I₁ and I₂ in WUEs. Moreover, the combination between various irrigation frequencies and rates had an important effect on yield variables and WUEs, with the highest values being found for F₁I₂ and F₂I₁ and the lowest for F₃I₃ and F₄I₃. The F₁I₃ treatment had grain yield and yield components values similar to those obtained for the F₃I₂ and F₄I₁ treatments and WUEs values similar to those obtained for the F₂I₁ and F₂I₂ treatments. Seasonal yield response factors (k_y) were 1.81 and 1.86 in 2007 and 2008, respectively. Production functions of yield versus seasonal crop ET were linear for all combinations of irrigation frequency and rate and for all irrigation frequency treatments with the exception of the F₁ treatment, which instead showed a second order relationship. The relationship between WUE and grain yield was best represented by a power equation. In conclusion, we identified the optimal coupling combinations between irrigation frequency and water application rate to achieve the maximum yield and WUEs under either sufficient (F₂I₁) or limited irrigation (F₁I₃) water supplies.     

Energetics of hill agro-ecosystems: A case study from Central Himalaya

The present study analyses the energy budget of crop production in hill agro-ecosystems and discusses the relation between agro- and natural ecosystems. The cultivated area is divisible according to cropping pattern into (I) vegetable-based patterns and (II) wheat-based patterns. The values of input and output, in terms of energy, indicated minimum input for the wheat-soybean and maximum input for potato-cabbage-potato patterns among all cropping patterns. 1·7 times more output of energy is generated in vegetable-based ecosystems with an input of 25 times as much fertilizer, 151 times as much manure, 6 times as much seed and 6 times as much human labour as in the wheat-based system. Hill agriculture depends to a great extent on the surrounding forest ecosystem and represents centres of massive energy consumption.     

Consumptive water use and crop coefficients of irrigated sunflower

In semi-arid environments, the use of irrigation is necessary for sunflower production to reach its maximum potential. The aim of this study was to quantify the consumptive water use and crop coefficients of irrigated sunflower (Helianthus annuus L.) without soil water limitations during two growing seasons. The experimental work was conducted in the lysimeter facilities located in Albacete (Central Spain). A weighing lysimeter with an overall resolution of 250 g was used to measure the daily sunflower evapotranspiration throughout the growing season under sprinkler irrigation. The lysimeter container was 2.3 m × 2.7 m × 1.7 m deep, with an approximate total weight of 14.5 Mg. Daily ET _c values were calculated as the difference between lysimeter mass losses and lysimeter mass gains divided by the lysimeter area. In the lysimeter, sprinkler irrigation was applied to replace cumulative ET _c, thus maintaining non-limiting soil water conditions. Seasonal lysimeter ET _c was 619 mm in 2009 and 576 mm in 2011. The higher ET _c value in 2009 was due to earlier planting and a longer growing season with the maximum cover coinciding with the maximum ET _o period. For the two study years, maximum average K _c values reached values of approximately 1.10 and 1.20, respectively, during mid-season stage and coincided with maximum ground cover values of 75 and 88 %, respectively. The dual crop coefficient approach was used to separate crop transpiration (K _cb) from soil evaporation (K _e). As the crop canopy expanded, K _cb values increased while the K _e values decreased. The seasonal evaporation component was estimated to be about 25 % of ET _c. Linear relationships were found between the lysimeter K _cb and the canopy ground cover (f _c) for the each season, and a single relationship that related K _cb to growing degree-days was established allowing extrapolation of our results to other environments.     

Assessment of drip and flood irrigation on water and fertilizer use efficiencies for sugarbeets

Mismanagement of nitrogenous fertilizers has caused serious nitrate (NO₃) contamination in many flood-irrigated regions of the western US. Low-volume irrigation practices, such as drip irrigation, can offer an alternative approach for controlling NO₃ leaching and agricultural water use. The objectives of this study were to compare NO₃ movement through soils under flood and drip irrigation practices for sugarbeet production, and to evaluate the agronomic feasibility of implementing drip irrigation. A field experiment was conducted during the sugarbeet (Beta vulgaris L.) growing seasons of 1996 and 1997 in southeastern Wyoming, where NO₃ contamination is a continued concern and sugarbeet is a major cash crop. Three drip irrigation regimes, corresponding to 20, 35, and 50% water depletion of field capacity (designated as D1, D2, and D3, respectively), were compared against flood irrigation. The irrigation plots were treated with 112, 168, and 224 kg N ha⁻¹ (designated as F₀, F₁, and F₂, respectively). Sugarbeet (SB) yields and sugar contents under drip irrigation were higher (3–28%) than those with flood irrigation; yields and sugar contents for the drip systems were in the order of D1>D2>D3. For all of the irrigation applications, there was an increasing trend in yields with increasing fertilizer rates. Drip regime resulted in greater residual soil NO₃ (RSN) for both 1996 and 1997 seasons as compared to flood practices. Values of RSN in both years followed the trend: F₂>F₁>F₀. Soil NO₃ in all three drip regimes was higher (1.6–2.4 times) than that with flood irrigation. In the overall root zone, NO₃ concentrations between D1 and D2 were comparable, whereas both of those levels were lower than D3. Greater NO₃ concentrations with D3 were observed at all depths. The amount of applied irrigation water with the drip system was lower than that for flood irrigation. Agronomic water use efficiency (WUE) and fertilizer use efficiency (FUE) for drip irrigation were always higher than those for flood irrigation. In 1996, WUE and FUE maintained an order of D1>D2>D3. There was a decreasing pattern in FUE values with increasing fertilizer rates. The overall results indicated that SB production could be sustained with lower water and fertilizer use by using drip irrigation. The p-values (≤0.05), based on both F-test (p_f) and two-tailed student’s t-test (p_t), suggested a significant difference between the yield means obtained under drip and flood irrigation practices. As compared to the flood irrigation, the least p-values were obtained with D1 followed by D2 and D3, respectively, thus, confirming that D1 was the most effective treatment. The p-values for SB yields under comparative fertilizer treatments and same drip application showed no significant difference between the means, thus, suggesting the feasibility of using lower fertilizer rate while sustaining the targeted yield under drip irrigation. The comparative estimation of water losses by drainage between flood and drip irrigation suggested that the later practice reduced the quantity of water leaching beyond the root zone. Among the three drip treatments, the lowest drainage amount was observed with D1 as a result of its higher irrigation frequency and smaller quantity of water input during each application.