Lec16_Animal_Crops_08 - HORT 460 Cropping Systems Ecology...

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Unformatted text preview: HORT 460 Cropping Systems Ecology MODULE 111. Case Studies Mixed Animal-Crop Systems Livestock industries (for milk, eggs, meat, etc) have been transformed in many parts of the developed world in the past few decades to intensive, high animal-density systems that are often completely decoupled from the land where crops for animal feed (e. g., grasses and grain) are produced. Animals in these systems are often confined year round, and fed imported grain or other food stocks, rather than allowed to pasture feed. Reasons for this trend include powerful economic and social forces, such as economies of scale for efficient specialized “factory” farming, better quality control, cheap subsidized grain prices, and regional and global consolidation and marketing. This often leads to such concentration of animal wastes in animal production regions that environmental pollution occurs. Policies that emphasize economic efficiency while ignoring health and environmental risks lead to extemalization of many of the real costs of production to society, such as waste processing, transport of fertilizers, and other factors (Galloway et a1. 2002). Here we re-examine the potential for re—integration of animal-crop production systems to recycle nutrients, maximize efficiency of nitrogen-use efficiency, minimize adverse environmental impacts of animal production, and still maintain farmer profits. A. Excess Nitrogen and Phosphorus 1. Synthetic nitrogen (N) fertilizer Production of synthetic N fertilizers for crop production (whether for direct human consumption or for animal feed) has been increasing exponentially for much of the past century (Fig. 1). Use of synthetic nitrogen fertilizer has replaced use of legumes in rotation in many cropping systems. Synthetic nitrogen fertilizer production (the Haber-Bosch manufacturing process) is conducted at very high temperatures and is energy intensive (typically 4 — 6 tons of carbon (C) emitted (C02 equivalents) per ton N manufactured. Use of synthetic fertilizers also has a C cost associated with transport 2. Nitrogen use efficiency of animal vs. crop production a. Very little of the N fertilizer applied to crops actually ends up as protein N that we consume due to many losses and inefficiencies. Typically only about half of N applied to the field ends up in the crop, and then only a fraction of the crop N is actually harvested, ends up in food after processing and transport. When humans do not directly consume the crop, but instead the crop is fed to animals and then we consume the animals, the losses and inefficiencies are greater. A recent global analysis (Fig. 2. see Galloway and Cowling) found that for every 100 units of N fertilizer produced, only 14 end up in the crop consumed by humans. If the crop is instead fed to animals and humans consume the N as animal protein, only 4 units of N are consumed for every 100 units of N fertilizer applied. Some of the 16% typical loss from N in the crop to N harvested is recovered by plowing in crop residues, but most of the other losses, such as animal waste, are not recovered in specialized intensive systems. b. There are differences among major animal groups in the protein contents of food products and feed conversion efficiency (Fig 3). For example meat in the form of beef, pork, and chicken have protein conversion efficiencies of 5, 13, and 25%. 3. Nitrogen environmental issues a.. Excess N due to inefficiencies in crop and animal production lead to nitrate leaching into ground and surface waters, making water unsafe for human consumption (at levels above 10 mg/L). Nitrate in surface waters also can cause eutrophication (stimulation of algal blooms) and hypoxia (growing algae use us the oxygen in the water, leading to suffocation of fish and other aquatic organisms). Eutrophication and hypoxia associated with excess N is mostly a problem in marine ecoystems (estuaries, bays), while excess phosphorus is more of a problem in fresh water (lakes, ponds). b. Excess use of either synthetic or organic (e.g., manure) N sources can lead to large emissions of nitrous oxide N20, a greenhouse gas with 300,times more global warming potential on a molecule to molecule comparison basis than CO2. Globally, N20 emissions have been increasing exponentially for the past several decades, and N20 is the third most important greenhouse gas (behind CO2 and methane, CH4) contributing to global warmlng. 4. Phosphorus environmental issues Animal waste is high in P, and if this P escapes by runoff into waterways it, like N, leads to eutrophication and hypoxia. Phosphorus tends to be more of a problem in fresh water bodies (lakes, ponds), while excess N is more of a problem in marine waters (estuaries, bays). 5. Import of N and P into animal production areas A major problem with the decoupling of animal and crop production is that N and P in the form of crop—derived animal feeds and supplements are imported in large quantities to confined animal facilities, where these nutrients accumulate in huge concentrations in animal waste. B. Improving Efficiencies of Intense Confined Animal Production Facilities 1. One approach is to link intensive animal production facilities together with crop production in a region so that manure waste is recycled to crops, reducing input of synthetic nitrogen fertilizers and preventing concentration of animal waste and nutrients at one location (Fig. 4). 2. Another approach is to utilize and/or treat the animal waste in useful ways that minimize the potential for negative environmental impacts (e.g., capture of methane as a biofuel; composting) C. Incentives for Re—coupling Animal-Crop Production Systems 1. Mixed animal-crop systems reduce import of N and P into an area in the form of animal feedstocks (instead animal feed is grown on the farm as pasture grass, grains, etc. ) 2. Pasture feeding by ruminant animals is highly efficient as these grasses are not directly consumable by humans, and pastures can be sustained on marginal lands where crops could not otherwise be grown. 3. Mixed animal-crop systems allow recycling of animal waste as manure for crop fertilizer (Fig. 5). 4. Challenges of mixed animal-crop systems a. Farmer must have knowledge of both crops and animals, and must manage both. b. Local pasture growth and grain production is seasonal, not constant, while animal food needs continue year round. Timing of animal food needs increases during reproduction, lactation, rapid grth of young animals. c. Feeding animals local feed stocks as they are available can make quality control (e. g, meat quality) more difficult than feeding formulas of imported foods. D. Innovative Synergisms in Animal-Crop Systems 1. Cows, sheep, goats can live off of pasture grass/legumes that grow on marginal land where crops cannot be grown and convert this plant biomass to human consumable protein. 2. Sheep and goats can been used in orchards, vineyards, nut tree plantings for controlling height of grass/ legume ground covers between tree rows. This controlled grazing keeps the ground covers from becoming to competitive with the tree crops, the animals are fed at no extra cost to the farmer (except management costs), the animals provide fertilizer for tree crops and ground cover (Hardesty and Tiedeman 1996). 3. Chickens can be used: a. in a pasture paddock area after sheep or cattle to eat animal parasites, fly larvae, and spread animal manure; b. in and orchard or vineyard to clean up dropped fruit, debug the ground cover, clean near the base of the trees. c. in a greenhouse vegetable operation between crops to clean out bugs and provide fertilizer for the next crop 4. Pigs can be used to mix and stir old hay bedding of cows, sheep, horses arid turn it into useable compost. The bedding must first be seeded with grain to motivate the pigs to dig through the bedding. 5. Other examples, geared toward small farm operations, are provided in Salatin (1998). REFERENCES Galloway JN, EB Cowling, SP Seitzinger, RH Socolow. 2002. Reactive nitrogen: too much of a good thing? Ambio 31(2): 60—63. Galloway JN, EB Cowling. 2002. Reactive nitrogen and the world: 200 years of change. Ambio 31(2): 64-71. Hardesty LH, JA Tiedeman. 1996. Integrating crop and livestock production in Inland Northwest farming systems. Amer J Alternative A gric 1 1 :21—26. Loomis RS, DJ Connor. 1992. Crop Ecology. Cambridge University Press. Cambridge, UK. Oenema O, SPietrzak. 2002. Nutrient management in food production: achieving agronomic and environmental targets. Ambio 31(2): 159-168. Oltj en J W, J L Beckett. 1996. Role of ruminant livestock in sustainable agricultural systems. J Animal Sci 74:1406-1409. Salatin J. 1998. You Can Farm. Polyface, Inc. Swoope, VA. 1007 Nitrogen fertilizer consumption (Mt N/yr-1) USA l' l I 1960 * " r _ I 71970' , .Lgaiiil 519802731 i ‘ r ‘ 1 : r ‘1950 9‘0 12900 N Fertilizer N Fertilizer N N N N Produced Applied in Crop Harvested in Food Consumed 37-56??? N Fertilizer N Fertilizer N N N N Produced Applied in Crop in Feed in Store Consumed xvi-rm Figure 2. The fate of fertilizer N produced by the Haber-Bosch process from the factory to the mouth for (a) vegetarian diet, and (b) carnivorous diet. f , _ :- F3 , . g§wvli2002 ngquigj:ma4£ 0 Milk Carp Eggs Chicken Pork Beef Feed conversion (kg of feed/kg-1 of 0.7 1.5 3.8 2.3 5.9 12.7 live weight) Feed conversion (kg of 'feed/kg-1 of 07-17”; :5: V V ’ , 4,2,1; f '7';1 M 9731.7 edible weight), . r L o, r r ' r 7 Protein content (% of edible 3.5 18 13 20 14 15 weight) m Protein contents of major animal foods and feed conversion efficiencies of their production. (Based on Figure 8.4 in ref. 2.) Calculations of feed conversion efficiencies based on the latest (1999) average US feed requirements from ref. (49); they include the feeding requirements of entire breeding and meat-producing populations. Fig. <1 (WW via-Amixwtflflww W1) l5 “! r [695) 4% Conceptual diagram of changes in nutrient flows due to changes in nutrient flows at regional level. Region A contains specialized and segregated dairy farms, arable farms and pig farms, that heavily rely on imported feed and fertilizers. Region B depicts improvements in nutrient management at regional level through exchanges of animal feed and manure between farms and the return of nutrients in garbage and wastes from the processing industry, retail, and humans back to agriculture. As a result, imported nutrients and nutrient losses are lower in region B than region A Feed Fertilizer Fertilizer Feed Region A E Processmg industry 8» Retail ; g K ,, g e LE oer 2 a (U 2 Region B Processing industry & Retail 1 Waste - sewage - garbage - other (Ovfi’wuevwct Vi pffiiy-Zfiifi [1002 rlqhé‘y 31(2) : Me) Fig 5" , .. Conceptual diagrams of specialized crop and animal production systems (a and c) and mixed farming systems (b). Inputs of nutrients are plotted left, outputs on the right-hand side. In mixed farming systems, there is an intensive recycling of nutrients. a. Specialized crop production system inputs outputs ‘r F crop products N2 fixation deposition fertilizer . v y . 1- l V in} losses manure inputs outputs feed animal products crop products N2 fixation «- « up, losses deposition ‘ fertilizer a « ‘ -> losses inputs outputs feed « / 7’ animal products up. losses ...
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Lec16_Animal_Crops_08 - HORT 460 Cropping Systems Ecology...

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