Significance of Soil Health
What The Experts Say
If soils are managed sustainably, they can de-carbonize the atmosphere and reduce the greenhouse effect. Hence, they can play a crucial role in mitigating climate change by reducing GHG emissions because they can store carbon in its most stable forms for thousands of years. It is due to this reason that the soil contains much more organic carbon than both plants and the atmosphere do.
Dr Abid Niaz, Convener of Climate Change Cell at Ayub Agricultural Research Institute, Faisalabad and the Principal Scientist at Soil Bacteriology Section of Agricultural Biotechnology Research Institute, Faisalabad, explains the possible effects of climate change on Pakistan’s soil in the following words:
“Pakistan is ranked seventh among the countries most affected by climate change and these changes are having a negative impact on our soil resources. Temperatures are rising, periods of drought are increasing, crops are being damaged by floods and intense rainfall patterns, and windstorms are wreaking havoc on fruit trees and major crops. The soil fertility is already low and soil productivity is adversely affected by the shortage of water and fertilizers.”
While responding to the question as to how healthy soils can help us in coping with climate change, Dr Niaz said the organic matter in our soils typically ranges between zero and 0.5%. Nitrogen, phosphorus and potash are also deficient while other trace elements, especially zinc, iron and boron, are also in a miniscule quantity. Due to this, the immunity of plants weakens and they suffer a lot of damage while combating droughts and diseases. If water is sufficiently available and new and more drought-tolerant varieties are sown, it can help in fighting climate change. Similarly, early sowing and early harvesting with the help of modern tools is also of pivotal importance in this regard.
Sharing his thoughts on the soil condition in Pakistan, Dr Niaz said, “Since fertility of Pakistani lands is very low, climatic changes affect them more. Water-logging and salinity are also on the rise. Groundwater is saline and is adding to the amount of salinity in our lands, which is, in turn, reducing their productivity.”
Answering a question as to how the threats to soil health and fertility in Pakistan can be reduced, Dr Niaz said, “Cultivation through modern machines, use of new varieties, sufficient availability of canal water, balanced and proportionate use of fertilizers and knowledge about the scientific analysis of the soil are very important tools in this context. If we do not take preventive measures, the risks and threats will increase and the country’s future and its soil resources will get jeopardized. Unnecessary and disproportionate use of fertilizers and pesticides will further contribute to climate change by increasing GHG emissions.”
While addressing the question that what forms of pollution affect the health and fertility of the soil and how can they be controlled, Dr Niaz opined that various forms of pollution like air pollution, land pollution, crop pollution, pollution from untreated sewerage and heavy metal pollution by using wastewater from factories, mills and houses for irrigating vegetables and fodder are on the rise and there is an urgent need to curb all these.”
Dr Niaz further asserts that the United Nations Sustainable Development Goals are directly related to the production of healthy soil and air pollution-free crops.
Human activities over thousands of years have left a grim legacy of contaminated soil around the world. About 50,000 to 100,000 industrial chemicals are now being commercially produced on a large scale, and their production is expected to grow by 3.4 percent annually until 2030. Sprawling cities are generating ever-increasing amounts of municipal solid waste and 80% of that is not recycled; thus, ending up in landfills and further polluting our soils. The agrochemical market is growing at 3.2% every year. Moreover, around 58% of agricultural soils in Europe contain residues of pesticides, half of which are now illegal. Big mineral-producing countries host around four billion people where, due to soil contamination, agricultural productivity has reduced by 40%. Besides, the number of cars plying worldwide will almost double by 2040. Highways are large, open and mobile sources of pollution from which heavy metals and toxic organic pollutants mix into the air to pose a formidable threat to adjacent agricultural soils and urban areas. Soils act as sponges and filter against pollutants. But when there is too much pollution in it, the pollutants can also be released. Food plants can absorb the pollutants in the soil through their roots and produce unsafe food. A manifestation of it is that one in 10 people in the world gets sick after eating contaminated food, and every year 420,000 thousand people die from such food because seven tablespoons of lead can contaminate one hectare of soil or 200,000 litres of water.
Healthy soils with high organic content can store large amounts of water that helps sustain food production as well as combat floods and droughts. Prudent soil-moisture management is essential for sustainable food production. Water is the ‘life’ and that’s true for agriculture as well. The ability of soil to accept, retain, release and transport nutrients enhances its productivity. This characteristic of fertile soil is also significant in that the biggest challenge in the near future is going to be increasing the production of food with less use of water. Since most smallholder farmers in developing countries depend on rain-fed agriculture; therefore, improving and managing soil moisture is essential. If healthy soil enhances crop growth, plants, grasses and trees also protect the soil from erosive agents like water and wind, and improve its structure.
Commenting on the fertility of Pakistani soil, Dr. Rashid Mehmood, Chairman of the Department of Soil Science, Punjab University, Lahore, talked about its diversity and said that some soils are very fertile while some have average and some very poor fertility. He elaborated: “Actually, with the word ‘fertility’, we refer to the ability of the soil to provide nutrients to plants. There are 17 total nutrients that we call ‘essential nutrients’ for plants. Plants take three of them, i.e. carbon, oxygen and hydrogen, directly from the air while 14 are to be provided by the growers. Three of these 14, nitrogen, phosphorus and potash, are to be provided in much higher quantities while calcium, magnesium and sulphur are required in relatively less quantity while the rest are micronutrients which are not required much. But, unfortunately, almost all Pakistani lands are deficient in nitrogen, phosphorus and potash, and fertilizers are recommended to make up for this deficiency. Although our soils require trace amounts of some nutrients like boron, iron, copper, manganese and zinc; even they are not present. And, farmers should use them every other third year – or in small amounts every year – if they want higher yields.
Hardness of the soil, high salinity and lack of proper preparation of it are some factors that hamper a plant’s ability to extract nutrients, even if they are present in the soil. Therefore, we have to plant crops that maintain the health of the soil and keep it in its place. To maintain the health of the soil, we should plant such crops that can add nutrients to the soil and refresh it a bit. For example, along with wheat, rice, cotton and sugarcane, we should also plant crops that fix nitrogen in the soil, such as garlic, cumin, pulses, etc. so that the land stays healthy. And, if possible, land should be left vacant for some time. In rain-fed areas, the land sometimes gets a little breather due to lack of rain, but in irrigated areas, crops are grown regularly.
Have recent floods affected our soil adversely or were these actually beneficial for it is an important question to which Dr Mehmood responded by saying: “It depends on the area and the place we are talking about. If the floodwater passes through sloped areas, its flow will be so fast that it will wash away the soil. But in planes, its speed is slow and thus it recedes there and leaves a layer of soil. The latter is a small issue as compared to the hugely problematic runoff. Secondly, when water passes through dry or water-logged lands, it stagnates there, adding further to the water-logging problem. The principal reason behind the stagnation of floodwater is that water table in such areas is already high. And, as regards whether it is beneficial or not, I would say that the assessment of it will be possible only through a scientific study because if water has passed through contaminated soil, it will bring this contamination to the lands coming in its way and if it has passed through healthy soil, it will bring healthy soil. Therefore, it is difficult to say something sans any scientific study.”
An overwhelming chunk of Pakistan’s land has been cultivated by using traditional plough for decades. It is used for loosening or turning the soil before sowing seed or planting to a fixed depth of 7-8 cm. Continuous ploughing to this depth results in a relatively compact layer of soil known as the ‘plough pan’ over a large part of the cultivated area. The plough pan, which is 8-20 cm deep, appears especially in soils that are high in silt. It creates a hindrance in the infiltration of water under the soil. Due to this, water-logging takes place and the drainage capacity of the soil is drastically reduced, thus crop cultivation is hampered by high soil moisture.
Diversified farming practices promote sustainable soil management. One of these practices is the cultivation of pulses. Pulses can be strategic allies in maintaining and enhancing the health of the soil, restoring degraded soils, and improving overall human health. Farmers have known since the dawn of agriculture that legumes are important to soil health, and agricultural techniques such as intercropping and crop rotation have been used for thousands of years. Pulses also play a role in increasing the organic content of the soil, improving its structure and maintaining biodiversity, thereby increasing overall soil health. Being leguminous crops, pulses’ roots add to soil fertility after rotting. Their cultivation helps in fixing nitrogen content in the soil, so they require less of both organic and synthetic fertilizers. The nitrogen-fixing properties of pulses improve soil fertility, which improves and increases farm productivity.
Dr Shahid Riaz Malik, Principal Scientist/Program Leader at Pulses Department of National Agricultural Research Center (NARC), Pakistan Agricultural Research Council (PARC), Islamabad, while describing the importance of pulse cultivation for soil fertility, said, “One of the global challenges of the 21st century is to produce food for eight billion people without polluting the soil, environment and atmosphere. To meet this gigantic challenge, pulses can play an important role in the agricultural system. Cultivation of pulses has beneficial effects on the chemical and physical structure and health of the soil. Nature has the ability to make natural nitrogen fertilizer in pulses. Special types of bacteria in the ground (nitrogen-fixing bacteria) live in the roots of pulses by forming small grains, called nodules. These bacteria feed on leguminous plants and, in turn, increase soil fertility by fixing nitrogen content. This nitrogen fertilizer not only fulfils pulses’ requirement but can also be used for other crops sowed after their harvest. As per a study, different varieties of pulses produce 10 to 120 kg of nitrogen fertilizer per acre. Some bacteria in the soil benefit plants by dissolving the insoluble phosphorus in the fertilizer. Thus, by cultivating pulses, we can increase soil fertility and reduce the need for synthetic nitrogen fertilizers which are not environment-friendly. In the farming system, where pulses are grown, very little CO2 is emitted into the atmosphere; that’s why pulses are called eco-friendly crops. The leaves and roots of pulse plants are added to the soil to increase its organic content, which increases the fertility of the soil, improves its structure and augments its water-absorption capacity. Mixed cropping or the inclusion of pulses in crop rotation helps control many crop diseases and eliminate pests. In this way, the use of synthetic poisons is reduced that helps in reducing soil, air/environmental pollution. Cultivation of pulses is also very beneficial for less fertile and barren lands, and by continuous cultivation, the land fertility begins to increase. Later, other crops can be cultivated there.”
When asked under what schedule pulses should be cultivated so as to increase soil fertility, Dr Malik said, “Cultivation of pulses between two crops increases the fertility of the land/soil. A farming system in which crops that take nutrients from the soil – wheat, rice, maize, sugarcane, cotton, etc. – are grown in succession requires more fertilizers. Pakistan’s agricultural system features an overwhelming farming of wheat and rice. In such a system, the pulse crop mung should be cultivated after the wheat harvest or farmers should cultivate gram or lentil after rice harvest. In rain-fed areas like Pothwar region, wheat crop is planted in a year and the land is left vacant during Kharif or monsoon season. By successfully planting mung beans and urad beans in the Kharif season, farmers can not only increase their income but are also able to restore the fertility of the land. In areas where sugarcane is grown in spring, pulses can be intercropped with mung as it can help in meeting the nitrogen fertilizer requirement of the sugarcane crop. In the areas where sugarcane is grown in autumn, mixed cultivation of pulses, chickpeas and lentils can be done. Apart from this, it can be used in mixed cultivation of pulses in different orchards such as malt, mango orchards.”
Soil health is the capacity of soil to function as a living system. Healthy soils maintain a diverse community of soil organisms that help to control plant disease, insect and weed pests, form beneficial symbiotic associations with plant roots; recycle essential plant nutrients; improve soil structure with positive repercussions for soil water and nutrient holding capacity, and ultimately improve crop production. Healthy soil prevents pollution of the environment and contributes to mitigating climate change by maintaining or increasing its carbon content. Due to these factors, healthy and productive soils are central to achieving many of the 17 Sustainable Development Goals adopted by the United Nations General Assembly. But the planet’s soil is under pressure from climate change, population growth and poor land management, and this direly needs attention.
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