The role of phosphorus particularly its
essential use in agricultural farm land (nearly 82 % of various uses) from a
non-renewable and limited global stock of rock phosphate has been a major
concern from the point of view of its inappropriate use or mismanagement
vis-a-vis significant losses in various forms leading not only to exhaust the
present stock within a few decades but also to cause
serious environmental problems. The total production of mined phosphate rock in
short-medium term for agriculture and industry is 20 MMT of P per year, and the
P demand likely to increase at an average rate of 2-3 % per year to result in
peak production by 2040, and eventually the supply to fall short of demand within
finite time frame. It is not far that the P reserves will be controlled by
countries like Morocco, Senegal, Western Sahara, China, South Africa, Jordan
and US while farmers from the rest of the world have to depend on the terms set
by them - a geo-political factor.
Fig. 1. The phosphorus cycle (Source: http://www.euwfd.com/html/sources_of_pollution_-_diffuse_pollution.html)
The P cycle (Fig. 1) shows major losses in the form of runoff and erosion, leaching through soil causing global epidemic of eutrophication in fresh water, estuarine and near shore ocean environments, loss in potable water resources, aquatic biodiversity and formation of large ocean “dead zones“. Using P more efficiently and recovering it for reuse should contribute to reducing such pollution. The global reserve of rock phosphate was estimated as above 60000 MMT towards the end of the last century. Most of the countries including India has however no policy to manage P as a critical global resource, like what the EU Water Framework Directive has, urgently requiring them to be developed, as urged by the Global Phosphorus Research Initiative, which should, in the first hand, ensure positive P balance in farm lands. The present status suggests, if we take into account applications of mineral fertilizers and manures, the balance from some Western European countries is positive, particularly in the Netherlands, where it exceeds 39 kg P ha-1 each year (Liu et al., 2008). For other countries in the region, the value ranges from 8.7 to 17.5 kg P ha-1 annually (Johnston and Steen, 2000). China also achieved a positive balance around 1980 at the national level, in parallel with increasing application of synthetic fertilizers (Wang et al., 1996; Jin and Portch, 2001). In 2000, the national surplus of P in Chinese soils was estimated at an average of 16 kg ha-1 (Liu et al., 2007). The total P budget for world’s cropland estimated in 2004 suggests (Liu et al., 2008) in the form of annual fluxes (MMT P): Inputs 22.9, Removals 12.7, Losses 19.8, and finally the Balance -9.6.
Literatures cited
1.
Jin,
J.Y. and Portch, S. (2001). Recent
agricultural and fertilizer developments in China. Paper presented at IFA
Regional Conference for Asia and the Pacific, 10-13 December, Hanoi, Viet Nam.
2.
Johnston,
A.E. and Steen, I. (2000). Understanding
phosphorus and its use in agriculture. European Fertilizer Manufacturers
Association (EFMA), Brussels, Belgium.
3.
Liu,
Yi, Chen, J.N., Mol, A.P.J. and Ayres, R.U. (2007). Comparative analysis of
phosphorus use within national and local economies in China. Resources,
Conservation and Recycling, 51(2): 454-474.
4.
Liu,
Yi, Villaba, Ayres, R.U. and Schroder Hans (2008). Global phosphorus flows and
environmental impacts from a consumption perspective. Journal of Industrial Ecology, 12(2): 229-247.
5.
Wang,
Q.B., Halbrendt, C. and Johnston, S.R. (1996). Grain production and
environmental management in China’s fertilizer economy. Journal of
Environmental Management, 47(3): 283-296.
Dipankar Ghorai1 & HSSen2
1.
SMS
(Agril.) & Incharge, KVK (ICAR-CRIJAF),
Budbud,
Burdwan, Email:dipankarghoraikvk@gmail.com
2.
Former
Director, ICAR-CRIJAF,
Email:
hssen.india@gmail.com,hssen2000@hotmail.com
No comments:
Post a Comment