Human-induced nutrient output, driven primarily by the increasing demand for food production, has had a tremendous impact on the earth’s biogeochemical cycles. Since the 1960s, chemical fertilizer use has played an important role in increasing crop yields; manure has been recognized as a source of soil nutrients for centuries and has contributed a great portion of the nutrient input to the land surface. Manure production is expected to increase in the coming decades due to the growing demand for livestock populations, the ever-increasing human population, and increasing dietary preferences for more meat consumption. Recovering phosphorous from animal manure could potentially satisfy 90% of agricultural demand. To determine the status of unevenly distributed nutrient at large scales, it is critical to have an accurate understanding of the geographic distribution of nutrient inputs from different sectors. In spite of extensive studies in the development of nutrient data at both regional and global scales, most previous datasets for manure nutrient production at a global scale either 1) relied on a livestock population dataset with coarse resolution or 2) were only available for limited time periods without consecutive inter-annual variation, e.g., Herrero and Thornton, (2013), and Potter et al., (2010). The Gridded Livestock of the World offers an exceptional opportunity to improve manure data upon earlier studies and expand knowledge of manure production to a period of approximately 60 years. The major objective of this study is to produce global gridded maps of manure nutrient production at a 5-arcminute resolution in latitude by longitude during 1961-2017.
Results/Conclusions
The estimated manure nitrogen production increased from 74.9 Tg N yr−1 in 1961 to 131.0 Tg N yr−1 in 2014 with a significant annual increasing trend (1.0 Tg N yr−1, p < 0.01) and the estimated manure phosphorous production increased from 13.4 Tg P yr−1 in 1961 to 25.4 Tg P yr−1 in 2017 with a significant annual increasing trend (0.2 Tg P yr−1, p < 0.01). Cattle dominated the manure nitrogen production and contributed∼44 % of the total manure nitrogen production in 2014, followed by goats, sheep, swine, and chickens. Cattle also dominated the manure phosphorus production and contributed∼54 % of the total manure nitrogen production during 2011-2017, followed by swine, goats, chickens and sheep.