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Feed and manure use in low-N-input and high-N-input dairy cattle production systems: The need for more uniform terms and measures of nitrogen use efficiency in agricultural production
- Powell, J Mark
- Environmental Research Letters 2014 v.9 no.11 pp. 10-64
- ammonia, animal manure management, barns, biomass, body weight, case studies, cattle production, crop yield, cropland, dairy animals, dairy cattle, emissions, excretion, feces, feeds, fertilizers, food grains, forage, forage production, heifers, milk production, millets, nitrous oxide, nutrient use efficiency, people, production technology, recycling, sheep, soil conservation, Niger, Wisconsin
- In most parts of Sub-Saharan Africa fertilizers and feeds are costly, not readily available and used sparingly in agricultural production. In many parts of Western Europe, North America, and Oceania fertilizers and feeds are relatively inexpensive, readily available and used abundantly to maximize profitable agricultural production. A case study, dairy systems approach was used to illustrate how differences in feed and manure management in a low-N-input dairy cattle system (Niger, West Africa) and a high-N-input dairy production system (Wisconsin, USA) impact agricultural production and environmental N loss. In Niger, an additional daily feed N intake of 114 g per dairy animal unit (AU, 1000 kg live weight) could increase annual milk production from 560 to 1320 kg AU−1, and the additional manure N could greatly increase millet production. In Wisconsin, reductions in daily feed N intake of 100 g AU−1 would not greatly impact milk production but decrease urinary N excretion by 25% and ammonia and nitrous oxide emissions from manure by 18% to 30%. In Niger, compared to the practice of housing livestock and applying dung only onto fields, corralling cattle or sheep on cropland (to capture urinary N) increased millet yields by 25% to 95%. The additional millet grain due to dung applications or corralling would satisfy the annual food grain requirements of 2–5 persons; the additional forage would provide 120–300 more days of feed for a typical head of cattle; and 850 to 1600 kg ha−1 more biomass would be available for soil conservation. In Wisconsin, compared to application of barn manure only, corralling heifers in fields increased forage production by only 8% to 11%. The application of barn manure or corralling increased forage production by 20% to 70%. This additional forage would provide 350–580 more days of feed for a typical dairy heifer. Study results demonstrate how different approaches to feed and manure management in low-N-input and high-N-input dairy cattle systems impact milk production, manure N excretion, manure N capture, N recycling and environmental N loss.