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Fertilizer use in plantations and future implications

03 Dec 2013 - {{hitsCtrl.values.hits}}

It has been said that with the rising incidences of chronic kidney diseases in the agricultural areas of the island, the Sri Lankan government is taking measures to control the indiscriminate usage of chemical fertilizer and agrochemicals by the farmers.

According to the government, the country is experiencing adverse effects of the use of chemical fertilizer and agrochemicals introduced to increase crop productivity and ensure food security.

Although Sri Lanka has become self-sufficient in rice and some other crops, the adverse effects of chemical usage such as damage to bio-diversity, contamination of water and soil due to chemical substances leading to various health problems, particularly renal diseases in agricultural areas such as North Central and Eastern Provinces, are becoming costly for the country.

According to a World Health Organization (WHO) study, in recent years, a significant increase in Chronic Kidney Disease of uncertain etiology cases has been observed in some parts of Sri Lanka, especially in North Central, North Western, Ova and Eastern provinces.

A joint research project conducted by the government and the WHO found that the high prevalence of chronic kidney disease in the country’s main agricultural production regions caused by fertilizer and pesticide use.

The Health Ministry, which commissioned the WHO study, says the number of affected people in the country had grown to 450,000 although uncertainty prevails over the exact cause of the kidney disease.

The government has therefore, initiated measures to control the use of agrochemicals and fertilizer consumption and promote the use of organic fertilizer in farm lands.

Other side of the story
Fertilizer seems to have a bad name, and in some surprising circles. It is time to dispel some myths about mineral fertilizers, to appreciate the role they play in feeding the world, and to assess how best they can help agriculture meet the challenges it faces in the decades ahead.

There is a general consensus about the way agriculture is evolving in response to demographic and economic trends. World population will probably peak at some 8,000 million around 2030, when two out of every three people will live in towns and cities. Rising incomes will create a disproportionally higher demand for food, meaning that over the next three decades food production will need to increase by about 60 percent.

Nearly all of the increase in production will have to come from developing countries through intensification of agriculture, i.e. more yield per unit time and per unit area. As urbanization reduces the rural workforce, agriculture will also need to adopt new forms of mechanization and shift to land use intensification, with all of its connotations. Those scenarios point to an increase in use efficiencies of all natural resources, particularly water, and to the need for greater - although not proportionally greater - use of mineral fertilizer.

FAO’s study World agriculture: towards 2015/2030 says “increased use of fertilizer is becoming even more crucial in view of other factors, such as the impact on soil fertility of more intensive cultivation practices”. However, increases in food production are possible with a less than proportional increase in fertilizer nutrient use. For example, the study says, maize farmers in North America have increased nutrient use efficiency by adopting improved management practices. Other research suggests that techniques such as precision agriculture could help substitute “information for fertilizer”. See World agriculture: towards 2015/2030.

Yield increases
Half a century ago, farmers applied only 17 million tonnes of mineral fertilizers to their land. Today, they apply eight times as much. In northern Europe, fertilizer use has increased from about 45 kg/ha to 250kg/ha since 1950. In the same period, wheat yields in France increased every year, from about 1.8 tonnes/ha to more than 7 tonnes/ha. The growth in fertilizer use is certainly lower than the increase in yields, and confirms the overall pattern of increasing efficiency in fertilizer use.
Fertilizer application currently accounts for 43 percent of the nutrients that global crop production extracts each year, and the contribution may be as high as 84 percent in the years to come. Contrary to some public opinion, non-mineral nutrient sources are unlikely to challenge mineral fertilizer in the future: while there will be more manure available as livestock production increases, and urbanization produces more waste, especially sewage, their efficiencies are considerably lower and the current cost of using waste for crops is still quite high.

Organic agriculture, which eliminates the use of synthetic inputs, does not appear to be a feasible alternative. FAO, has done some very tentative calculations of what organic agriculture would mean on a global scale if market demand for organic produce increased substantially. The consequences are quite staggering: a large amount of land that would have to be brought under rotation with legumes or under animal production to make up for the lack of mineral fertilizer. While organic agriculture does fill a niche market, its limits - and its dangers, in terms of nutrient depletion - need thorough review.

The question is not whether but by how much fertilizer use will need to increase. At the World Food Summit in 1996, governments committed themselves to halving the number of hungry people by the year 2015. There is a direct link between that WFS goal and fertilizer use. Possibly, it means an 8 percent increase in fertilizer applications compared to the “business-as-usual” scenario. That does not seem very much, but in terms of its tonnage, it is considerable. Enhanced fertilizer use to meet WFS goals is particularly important in countries such as China and India, which make up a large proportion of the world population. But it may be even more important in Asia, where increases of 2.7 percent or more a year are needed in order to make up for nutrient losses, and in the humid tropics, where unfertilized annual cropping takes a heavy toll of soil organic matter.

Fertilizer use efficiency
Improving the efficiency of fertilizer use is the challenge of the future. One possible direction is improving fertilizer use and plant nutrient uptake efficiency through biotechnology. Hardly any current work in biotechnology addresses abiotic stresses or biological nitrogen fixation. While there may be scope for such research, we should be very careful about promising too much, too quickly. In any case, there is still a lot to gain from conventional plant breeding. For example, considerable work has been done on the so-called “staying green” characteristics of crops such as sorghum - the longer the crop stays green, the more fertilizer uptake there is over time.
Another promising area for research is soil biology. Although it remains an isolated field, we do know that soil organic matter and soil biology are important in nutrient management, and that nutrient recovery for fertilizer is much better with soil improvement. In Asia, where the recovery of nutrients is very low, more systematic work is needed on soil organic matter and on soil quality in physical, biological and chemical terms. Since biological nitrogen fixation produces mixed results, scientists need to link it to the application of more conventional fertilizers and study recovery. Results would probably show that biological nitrogen fixation is not a miracle solution by itself, but is successful under certain conditions.

Integrated management
Integrated management of production systems offer a proven path to greater fertilizer use efficiency. Remarkable results in rationalizing pesticide application have been achieved by making farmers more aware of integrated pest management through field schools, where they learn to observe crops closely and discuss the management of the pests and pathogens. These activities are increasingly linked to integrated nutrient management - farmers are being trained to observe the real impact of nutrient application rather than, for example, applying more and more urea simply because it is the cheapest fertilizer. Farmers also need to understand the effects of over-use of nitrogen on certain pathogens and other stress factors in crops. This may convince them of the need to buy non-nitrogen fertilizer and adopt much more balanced fertilizer applications.

Plantation tree crops
In Plantation Tree crops, plant organs particularly leaves are analyzed to determine the nutrient content in the sample and hence in the selected stand of the crop, with a view to utilizing the data to improve fertilizer use efficiency and to confirm visual symptoms.
Interpretation of soil analysis allows for assessing fertilizer needs, but it does not allow us to evaluate the efficiency or sufficiency of nutrient uptake to ensure optimal growth and productivity of the crop(s).

Private/public partnerships
The gains to be made from fertilizer use efficiency, even from a purely economic standpoint, could be significant. However, those gains depend on a broad range of factors that determine fertilizer use and fertilizer application by farmers. We need private/public partnerships, much better systems of distribution and quality control, and the array of marketing tools that goes with it.

The fertilizer industry should become more creative in ensuring that the farmer actually obtains the maximum benefit from existing crop and fertilizer application techniques. This means looking systematically at ways of reducing labour demand, which is particularly important as the availability of agricultural labour declines. For example, new polymer-coated fertilizers could offer a much better recovery rate. The industry should also look at the total cycle of nutrient use and nutrient recovery, remembering that the automobile manufacturing industry heard the same plea 20 years ago and has since made considerable progress.
There is still a lot of misunderstanding and confusion about soil nutrients and, in particular, mineral fertilizers. The public needs objective, science-based information from all partners involved in nutrient management. We must, in other words, tell people what we know. We know productivity gains are necessary and possible. We know that more fertilizers are needed. We know that fertilizer use can be far more productive and efficient, if we do it in the right way and in the right context. Use organic manure alone is not the answer. Let us look at the indiscriminate use of other agro chemicals that are being very vigorously promoted by the private sector, other than the mineral fertilizers.

(The writer can be contacted at [email protected])

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Fertilizer use in plantations and future implications

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