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Nitrogen and phosphorus excretion on mountain farms of different dairy systems

机译：不同乳制品山区农场的氮和磷排泄

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We developed a procedure to estimate the release of nutrients into the environment on Alpine dairy farms and applied it to a sample of 564 farms in the Province of Trento (north-eastern Italy) as a case study. Farm data (geographical location, herd size, milk production and quality, reproductive events, land use) were gathered from institutional databases and merged. Information on the formulation of the ration was obtained from farm visits. The farms fell into 4 groups: traditional with summer transhumance to highland pastures (T-ALP, 51%), traditional without transhumance (T-noALP, 24%), traditional using silage (T-S, 5%), and modem (MOD, 20%). The model predicted N and P excretion from cows and heifers on a farm basis. The N in manure was computed from total N excreted, assuming a 28% of N loss due to volatilisation. A cow unit was defined as the cow and its share of replacement heifer. The average dietary N content of the lactating cows ranged from 20 to 30 g/kg DM, while on-farm N excretion ranged from 90 to 190 kg/year per cow unit; the modern farms had the highest average value (137 kg), the T-ALP farms the lowest (106 kg). Average P excretion ranged from 10 to 40 kg/year/cow unit. The on-farm N and P in manure per unit of milk decreased asymptotically with increasing cow productivity, from 25 to 19 and from 4.1 to 2.8 g/kg milk, respectively. The modem farms had the greatest amounts of N and P in manure per unit of agricultural land (260 and 51 kg/ha, respectively), the T-ALP farms the lowest (161 and 37 kg/ha, respectively). Within system, there was a huge variation among farms in the N and P load per unit of agricultural land, which was largely explained by the number of cow units per ha and by nutrient excretion per cow unit, but not by herd size or cow productivity. Within dairy system, the N and P contents of the rations for lactating cows were weakly related to the daily milk yield, but strongly related to the annual excretion of the nutrient per cow unit. The farm N loads were below the legal thresholds (340 kg N/ha per year), but the geographical distribution of the loads indicated two critical areas due to farm density.
机译：我们制定了一种估算高山乳制品农场营养成分的营养成分的程序，并将其应用于特伦托（意大利东北部）的564个农场样本。农业数据（地理位置，畜群大小，牛奶生产和质量，生殖事件，土地使用）从机构数据库中收集并合并。有关配方的信息从农业访问中获得。农场落入4组：传统的夏季牧场对高地牧场（T-ALP，51％），传统的无转霉菌（T-Noalp，24％），传统使用青贮饲料（TS，5％）和调制解调器（MOD， 20％）。该模型在农场基础上预测了来自奶牛和小母牛的N和P排泄。粪肥中的n从排泄的总排泄中计算，假设由于挥发而产生的28％的损失。牛单位被定义为牛及其份额的替换小母牛。哺乳奶牛的平均膳食N含量范围为20至30g / kg DM，而在农场N排泄的范围为90至190公斤/年;现代农场的平均值最高（137千克），T-ALP农场最低（106公斤）。平均p排泄到10到40公斤/年/牛单位。每单位牛奶的粪便中的农场N和P分别随着牛生产率的增加而渐近，分别从25〜19和4.1至2.8g / kg牛奶增加。调制解调器农场每单位农业土地（分别为51千克/公顷）的粪便中最多的N和P，T-ALP农场最低（分别为161和37千克/公顷）。在系统内，每单位农业用地的N和P负荷的农场存在巨大变化，这主要由每人公顷的牛单位数量和每牛单位的营养排泄而解释，但不是畜群大小或牛生产率。在乳制品系统中，哺乳奶牛的口粮的N和P含量与日常牛奶产量略微相关，但与每牛单位营养素的年排泄有关。农场N负载低于法律阈值（每年340公斤），但负载的地理分布指示由于农场密度引起的两个关键区域。

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