The changes in livestock production and land use portrayed above also have important repercussions for the production, management and use of animal manure and fertilizers. Bouwman et al. (2005b) distinguished large ruminants (dairy and non-dairy cattle, buffaloes), small ruminants (sheep and goats), pigs, poultry, horses, asses, mules and camels for calculating the animal manure N production. The approach for distributing of animal manure over the two production systems, and within each system over different animal manure
management systems (grazing, storage, etc.), and calculation of ammonia volatilization in each system, are described elsewhere (Bouwman et al., 2005b).
The results show that the total N inputs from animal manure varied from less than 10 kg/ha/yr to more than 50 kg/ha/yr in 1995, and were highest in Western Europe and East Asia and much lower in world regions dominated by crop production systems and with less intensive livestock production. Inputs from animal manure will grow in all world regions in the coming three decades, except for Western Europe.
Within the latter region EU regulations for animal manure regarding usage of nitrogen inputs used will be bound to a maximum rate. Such rules have consequences in some countries with current high inputs, such as The Netherlands and Denmark. Atmospheric N deposition is generally highest in world regions with intensive livestock production (Bouwman et al., 2005b).
Global total N inputs from fertilizers and production of animal manure in agricultural systems have almost doubled between 1970 and 1995 from about 114 Tg/yr to 188 Tg/yr, whereby N manure contributed 83 Tg/yr or about 73% in 1970 and 104 Tg/yr (55%) in 1995. Bouwman et al. (2005b) estimated a total N input from fertilizers and animal manure of 238 Tg/yr, animal manure N being 127 Tg/yr (53%) and N fertilizer 110 Tg/yr (estimate for 2030) (Table 5.3).
Currently 22 Tg/yr of the total global amount of N in the animal manure production is not part of the agricultural system (16 Tg/yr) or is lost as NH3 from stored manure (7 Tg/yr). Stored manure may not be used, such as in many lagoon systems in North America, and manure is also used as a fuel or for other purposes in other, primarily developing countries. For example, for India a large part of the total amount of animal manure is excreted in forests, during roadside grazing or scavenging in villages and urban areas (Bouwman et al., 2005b; Van der Hoek, 2001), and is not part of the agricultural system.
Hence, the total amount of animal manure in agricultural systems has steadily increased between 1970 and 1995 and will continue to do so in the coming decades, but its share in total inputs has decreased from more than 70 to 55% in the past three decades, and will decrease at a slower rate in the coming three decades. The total quantity of nitrogen in animal manure that is available for spreading in mixed/industrial agricultural systems increased from 19 to 24 Tg/yr during the 1970-1995 period and according to the projection used it will increase further to 27 Tg/yr in 2030. The data show that the increase in the volume of animal manure N production increased less rapidly than the livestock production (Table 5.3). This is caused primarily by increasing productivity (Figure 5.3), mainly in the mixed/industrial systems, resulting in increasing nitrogen efficiency of the production system as a whole.
Was this article helpful?