一项研究发现，不同国家和地区的农耕土壤的磷浓度的影响有很大的差异，磷在一些地区过剩，而在另一些地区不足。在理想情况下，由化肥进入土壤的磷与农作物从土壤中吸收的磷是平衡的，但是Graham K. MacDonald及其同事报告说，这种平衡常常被打破。
这组作者使用详细的农业地图评估了2000年全世界各个地区的种植100多种农作物的栽培用土壤的磷浓度的平衡。尽管最广泛的严重缺磷存在于南美、美国北部和东欧的一些地区，磷大量过剩的地区主要在东亚大部分地区、美国沿海地区以及西欧和南欧的一部分。尽管化肥在很大程度上对磷过剩有贡献，在大量从事牲畜生产的地区——那里也常用粪肥——的磷浓度也过量。此外，缺磷的地区大致上也是种植饲料作物（用于饲养牲畜的作物）的地区。过多的磷可能进入水体，威胁淡水生态系统；相反，缺磷可能限制作物产量。因此，这些发现提示，需要谨慎地使用含磷化肥从而确保在不伤害水质的情况下的可持续的农业生产力。（生物谷Bioon.com）
生物谷推荐英文摘要：
PNAS doi: 10.1073/pnas.1010808108
Agronomic phosphorus imbalances across the world's croplands
Graham K. MacDonalda,1, Elena M. Bennetta,b, Philip A. Potterc, and Navin Ramankuttyd
Increased phosphorus (P) fertilizer use and livestock production has fundamentally altered the global P cycle. We calculated spatially explicit P balances for cropland soils at 0.5° resolution based on the principal agronomic P inputs and outputs associated with production of 123 crops globally for the year 2000. Although agronomic inputs of P fertilizer (14.2 Tg of P·y−1) and manure (9.6 Tg of P·y−1) collectively exceeded P removal by harvested crops (12.3 Tg of P·y−1) at the global scale, P deficits covered almost 30% of the global cropland area. There was massive variation in the magnitudes of these P imbalances across most regions, particularly Europe and South America. High P fertilizer application relative to crop P use resulted in a greater proportion of the intense P surpluses (>13 kg of P·ha−1·y−1) globally than manure P application. High P fertilizer application was also typically associated with areas of relatively low P-use efficiency. Although manure was an important driver of P surpluses in some locations with high livestock densities, P deficits were common in areas producing forage crops used as livestock feed. Resolving agronomic P imbalances may be possible with more efficient use of P fertilizers and more effective recycling of manure P. Such reforms are needed to increase global agricultural productivity while maintaining or improving freshwater quality.
