Adverse impacts of mineral fertilizers in tropical agriculture
Soil fertility is essential to meeting future food needs. Healthy soils store water, are home to a large share of biodiversity, and store carbon.
In recent years, there has been a resurgence in the use of mineral fertilizers to improve soil fertility. However, the idea that more fertilizer will produce higher yields is far too simplistic. On the contrary, industrial agricultural production is a major cause of lower soil fertility and rising soil degradation worldwide. The improper and disproportionate use of mineral fertilizers drives this trend.
A report published by Heinrich Böll Stiftung (Heinrich Böll Foundation) and WWF Germany provides an overview of the economic and ecological potential as well as the limitations and negative impacts of mineral fertilizers in the tropics and subtropics, focusing particularly on the situation facing smallholder farmers.
The report states that the negative ecological consequences of mineral fertilizers have reached menacing proportions, especially with respect to synthetic nitrogen. Adverse impacts include the reduction in humus content and biodiversity in the soil, soil acidification and emissions of nitrous oxide, a potent greenhouse gas causing climate change. The rise in soil acidity diminishes phosphate intake by crops, raises the concentration of toxic ions in the soil, and inhibits crop growth. The depletion of humus in the soil diminishes its ability to store nutrients. In summary, synthetic nitrogen destroys fundamental principles of agricultural production and jeopardizes future food security. So while synthetic nitrogen may bring about enormous short-term yield increases, it is, at the same time, harmful to the soil and climate – two elements that are fundamental to agricultural production.
Moreover, the economic efficiency of mineral fertilizers has fallen dramatically, as the price of fertilizers has risen much faster than that of food, transaction costs in developing countries are high, and soil fertility has fallen, which diminishes the efficacy of mineral fertilizers.
The report recommends that the use of synthetic nitrogen should be halted, and other nutrients integrated into a comprehensive soil fertility strategy. Techniques that maintain and enrich soil humus are key. Compost, animal manure, agroforestry, green manure and intensive fallowing can play a major role. Innovations are also needed in the production and application of mineral fertilizers so that they are harmless for the soil and the environment and allow nutrients to remain within the system. Correspondingly, the report recommends that synthetic nitrogen subsidies should be discontinued, and subsidies re-directed to building up soil fertility, including through ecological agriculture approaches.
We reproduce below the summary and political demands of the report. The full report can be downloaded at: http://www.boell.de/en/content/soiled-reputation-adverse-impacts-mineral-fertilizers-tropical-agriculture
With best wishes,
A soiled reputation: Adverse impacts of mineral fertilizers in tropical agriculture
Mineral fertilizers have never been used as much as they are today, and in developing countries they are experiencing a renaissance. But the efficacy of mineral fertilizers and the problems they entail have long been a matter of contention. This study provides an overview of the economic and ecological potential as well as the limitations and negative impacts of mineral fertilizers in the tropics and subtropics. It focuses on the situation facing smallholder farmers.
2 Over the past 60 years, agricultural intensification has relied on non-renewable resources, especially on the fertility of the soil. Many smallholder farming systems in Africa, Asia and Latin America, which are the source of income and food for several billion people, have been excluded from this development. The potential for raising productivity and production in many areas has yet to be exploited. The intensification strategies that have so far been pursued have been inappropriate. This study looks at the role that mineral fertilizers could nevertheless play in boosting agricultural productivity.
3 Our ability to produce enough food for an estimated 9 billion people in the year 2050 depends in part on an adequate supply of crop nutrients. Ensuring this supply is difficult because nutrients are unevenly distributed. Industrialized nations are oversupplied; many developing countries are underserved. The nutrient availability in soils is just as important. The soil’s capacity to absorb nutrients and to release them whenever needed for plant growth depends on various soil properties. The claim that mineral fertilizer is necessary to even out nutrient balances in the soil ignores a large part of the picture.
4 Mineral fertilizer production has risen almost constantly since the middle of the last century. Yet the consumption of fertilizers varies greatly from one region to another. The areas with the highest consumption are East and South Asia, while use in Africa is comparatively low. Big differences exist in the intensity of fertilization: from an average of 344 kg per hectare a year in China, to 7.5 kg in Ghana and just 2.7 kg in Rwanda. At the same time, the proportion of nitrogen among the main nutrients (which also include phosphorus and potassium) has continued to rise; today, nitrogen accounts for 74 % of the fertilizer used globally. Much is wasted.
5 Mineral fertilizer subsidies for smallholders have been common in developing countries for many years, and subsidy programmes are still popular. Current programmes show that food production can be increased significantly in regions where the food supply is short, though they fail to improve the soil fertility in the long term. Subsidies have a short-term effect, they do not result in sustainable food security, and they are of minimal importance to an economy’s profitability. What is more, subsidy programmes are a burden on national budgets. In some African countries, fertilizer subsidies account for up to 70 % of the funding assigned to agriculture.
6 Over the past decades, the economic efficiency of mineral fertilizers has fallen dramatically. This is because the price of fertilizers has risen much faster than that of food, transaction costs in developing countries are high, and soil fertility has fallen, which diminishes the efficacy of mineral fertilizers. In many tropical smallholdings, mineral fertilizer pays minimal dividends, if any at all.
7 The negative ecological consequences of mineral fertilizers have reached menacing proportions. This concerns synthetic nitrogen in particular. It reduces the humus content and biodiversity in the soil, causes soil acidification and gives rise to emissions of nitrous oxide, a potent greenhouse gas causing climate change that will harm future food production. The rise in soil acidity diminishes phosphate intake by crops, raises the concentration of toxic ions in the soil, and inhibits crop growth. The depletion of humus in the soil diminishes its ability to store nutrients. Greenhouse gases derived from excess nitrogen harm the climate. In summary, synthetic nitrogen destroys core fundamental principles of agricultural production and jeopardizes future food security.
8 The challenge, therefore lies in using mineral fertilizers in such a way that they are harmless for the soil and the environment and allow nutrients to remain within the system. The use of synthetic nitrogen should be dispensed with completely, and other nutrients must be integrated into a comprehensive soil fertility strategy. Techniques that maintain and enrich the soil’s humus content will be key to this. Compost, animal manure, agroforestry, green manure and intensive fallowing will all play a major role. Innovations are needed in the production and application of mineral fertilizers. The dominant acidifying fertilizers (especially urea, ammonium sulphate and ammonium nitrate) should be replaced by physiologically neutral fertilizers.
9 Mineral fertilizer is the embodiment of the finiteness of natural resources, fossil fuels, mineral deposits and soil fertility. Today’s use of nitrogen fertilizer poses a danger to tomorrow’s food security. Current approaches need to be overhauled in favour of the sustainable use of resources, while also boosting production. Politicians face four tasks:
* Stop promoting synthetic nitrogen
* Develop national strategies for a soil-fertility infrastructure development programme
* Establish focal points of research to support such a reorientation, and
* Develop scenarios for the transition away from using mineral fertilizers as a short-term consumption item to a long-term investment in soil fertility.
The limits to growth are becoming increasingly apparent, especially in agriculture. There is hardly a better example of this finiteness than mineral fertilizer.
Manufactured using large quantities of fossil fuels (mineral oil and natural gas) and relying in part on mineral deposits, the prices of mineral fertilizer have risen disproportionately as these resources become scarce.
Other limited resources are equally being wasted by mineral fertilizers. Synthetic nitrogen lowers soil fertility and reduces the impact of other fertilizers. The nitrogen fertilization of today is jeopardizing the food security of tomorrow. Both developments lead us to a dead end. Unviable fertilizer subsidies that eat up public funds will be unable to do anything to change this.
A change in mindset both towards a sustainable use of resources and production intensification is needed. In terms of nutrient use, fundamental changes are the order of the day. Decentralized and low-cost strategies that take care of the needs of smallholders are of key importance. The most important tasks facing policyholders today can be summarized as follows:
1 Synthetic nitrogen subsidies should be discontinued as a matter of principle. Instead, government or private subsidy programmes should be directed at building up soil fertility – as part of the infrastructure development of regions with degraded soil. This also includes incorporating organic nitrogen fixation into production systems through the cultivation of legumes.
2 Some of the most urgently required activities of a national “sustainable soil fertility infrastructure development” strategy include:
* Economic promotion aimed at tapping national phosphate and lime deposits; the build-up of production capacities and distribution systems for domestic mineral fertilizers.
* Economic promotion aimed at establishing urban composting facilities, which generate organic fertilizers for farms around cities, so enabling nutrients to flow back from urban to rural areas.
* Supporting farms that produce seed and planting stock for nitrogen-binding plants in order to allow agricultural land-use systems to make the wide- scale conversion to biological nitrogen supply.
* Re-focusing agricultural advisory services in which agricultural specialists are trained in sustainable land management to enhance and preserve soil fertility, and are mandated to make these a focal point of their activities.
3 A new, significant area of work will also open up for agricultural research. Great emphasis will be placed on fundamental research as well as issues of applied research; existing technologies need to be further developed and optimized and adapted to local environments. Key areas that need to be addressed when it comes to introducing sustainable intensification of cropping systems include:
* Improving the quality of soil humus content and its humic acid composition by managing and controlling composting processes.
* Developing mechanical, chemical, microbiological and organic processes to solubilize phosphate rocks for small-scale mineral fertilizer production facilities as an alternative to the large-scale processes that use sulphuric acid to make superphosphate.
* Developing cropping systems which not only achieve high yields but also fix sufficient quantities of nitrogen so that the synthetic version can be dispensed with (leguminous underseed, mixed cultures, agroforestry systems).
* Optimizing composting processes for domestic urban waste and analysing the fertilizing impact of this material.
* Developing processes to recycle human faeces back into agricultural land use systems.
4 All in all, such a change in strategy towards sustainable intensification is the result of a longer-term process, because technologies need to be tested and further developed, and the conditions adapted. Only by doing so can a collapse in food production be averted. Realizing this requires the development of strategies and concepts of transition. Strong resistance is to be expected. After all, the outlined system change runs contrary to a number of corporate interests (including a powerful oligopoly of fertilizer companies) which make a pretty penny from the current system of publicly-funded mineral fertilizer. Enabling mineral fertilizers to contribute meaningfully to food security requires a full and complete realignment of production, commerce and fertilization. Such a realignment has to make smallholder agriculture a focus. The results of this study show that the use of mineral fertilizers in the tropics and subtropics is only then justified if it is embedded in a concept that seeks to build up long-term soil fertility.