Practices that can cause long-term damage to
soil include excessive
tilling of the soil (leading to
erosion) and
irrigation without adequate drainage (leading to
salinization). The most important factors for a farming site are
climate, soil,
nutrients and
water resources. Of the four, water and
soil conservation are the most amenable to human intervention. When farmers grow and harvest crops, they remove some nutrients from the soil. Without replenishment, the land suffers from
nutrient depletion and becomes either unusable or suffers from reduced
yields. Sustainable agriculture depends on replenishing the soil while minimizing the use or need of non-renewable resources, such as
natural gas or mineral ores. A farm that can "produce perpetually", yet has negative effects on environmental quality elsewhere is not sustainable agriculture. An example of a case in which a global view may be warranted is the application of
fertilizer or
manure, which can improve the productivity of a farm but can pollute nearby rivers and coastal waters (
eutrophication). The other extreme can also be undesirable, as the problem of low crop yields due to exhaustion of nutrients in the soil has been related to
rainforest destruction. In Asia, the specific amount of land needed for sustainable farming is about which include land for animal fodder, cereal production as a cash crop, and other food crops. In some cases, a small unit of aquaculture is included (AARI-1996).
Nutrients Nitrates Nitrates are used widely in farming as fertilizer. Unfortunately, a major environmental problem associated with agriculture is the leaching of nitrates into the environment. Possible sources of
nitrates that would, in principle, be available indefinitely, include: • recycling crop waste and
livestock or treated
human manure • growing
legume crops and
forages such as
peanuts or
alfalfa that form symbioses with
nitrogen-fixing bacteria called
rhizobia • industrial production of nitrogen by the
Haber process uses hydrogen, which is currently derived from natural gas (but this hydrogen could instead be made by
electrolysis of water using renewable electricity) • genetically engineering (non-legume) crops to form nitrogen-fixing symbioses or fix nitrogen without microbial symbionts. The last option was proposed in the 1970s, but is only gradually becoming feasible. Sustainable options for replacing other nutrient inputs such as phosphorus and potassium are more limited. Other options include
long-term crop rotations, returning to natural cycles that annually flood cultivated lands (returning lost nutrients) such as the
flooding of the Nile, the long-term use of
biochar, and use of crop and livestock
landraces that are adapted to less than ideal conditions such as pests, drought, or lack of nutrients. Crops that require high levels of soil nutrients can be cultivated in a more sustainable manner with appropriate fertilizer management practices.
Phosphate Phosphate is a primary component in
fertilizer. It is the second most important nutrient for plants after nitrogen, and is often a limiting factor. It is important for sustainable agriculture as it can improve soil fertility and crop yields. Phosphorus is involved in all major metabolic processes including photosynthesis, energy transfer, signal transduction, macromolecular biosynthesis, and respiration. It is needed for root ramification and strength and seed formation, and can increase disease resistance. Phosphorus is found in the soil in both inorganic and organic forms Long-term use of phosphate-containing chemical fertilizers causes
eutrophication and deplete soil microbial life, so people have looked to other sources. However, rock phosphate is a non-renewable resource and it is being depleted by mining for agricultural use: or perhaps earlier.
Potassium Potassium is a macronutrient very important for plant development and is commonly sought in fertilizers. This nutrient is essential for agriculture because it improves water retention, nutrient value, yield, taste, color, texture and disease resistance of crops. It is often used in the cultivation of grains, fruits, vegetables, rice, wheat, millets, sugar, corn, soybeans,
palm oil and coffee. Potassium chloride (KCl) represents the most widely source of K used in agriculture, accounting for 90% of all potassium produced for agricultural use. The use of KCl leads to high concentrations of chloride (Clˉ) in soil harming its health due to the increase in soil salinity, imbalance in nutrient availability and this ion's biocidal effect for soil organisms.In consequences the development of plants and soil organisms is affected, putting at risk
soil biodiversity and agricultural productivity. A sustainable option for replacing KCl are chloride-free fertilizers, its use should take into account plants' nutrition needs, and the promotion of soil health.
Soil , India]
Land degradation is becoming a severe global problem. According to the
Intergovernmental Panel on Climate Change: "About a quarter of the Earth's ice-free land area is subject to human-induced degradation (medium confidence). Soil erosion from agricultural fields is estimated to be currently 10 to 20 times (no tillage) to more than 100 times (conventional tillage) higher than the soil formation rate (medium confidence)." Almost half of the land on earth is covered with dry land, which is susceptible to degradation. Over a billion tonnes of southern Africa's soil are being lost to erosion annually, which if continued will result in halving of crop yields within thirty to fifty years. A comparative study of two adjacent wheat farms—one using sustainable practices and the other conventional methods—found that the sustainable farm had significantly better soil quality, including higher organic matter, microbial populations, and nutrient content, while also showing 22.4% higher net returns due to lower input costs, despite slightly lower yields. Improper
soil management is threatening the ability to grow sufficient food.
Intensive agriculture reduces the
carbon level in soil, impairing soil structure, crop growth and ecosystem functioning, and accelerating
climate change. Modification of agricultural practices is a recognized method of
carbon sequestration as soil can act as an effective
carbon sink. Soil management techniques include
no-till farming,
keyline design and
windbreaks to reduce wind erosion,
reincorporation of organic matter into the soil, reducing
soil salinization, and preventing water run-off.
Land As the global population increases and demand for food increases, there is pressure on land as a resource. In
land-use planning and management, considering the impacts of
land-use changes on factors such as soil erosion can support long-term agricultural sustainability, as shown by a study of Wadi Ziqlab, a dry area in the Middle East where farmers graze livestock and grow olives, vegetables, and grains. Looking back over the 20th century shows that for people in poverty, following environmentally sound land practices has not always been a viable option due to many complex and challenging life circumstances. Currently, increased
land degradation in developing countries may be connected with rural poverty among smallholder farmers when forced into unsustainable agricultural practices out of necessity. Converting big parts of the land surface to agriculture has severe environmental and health consequences. For example, it leads to rise in
zoonotic disease (like the
Coronavirus disease 2019) due to the degradation of natural buffers between humans and animals, reducing biodiversity and creating larger groups of genetically similar animals. Land is a finite resource on Earth. Although expansion of agricultural land can decrease
biodiversity and contribute to
deforestation, the picture is complex; for instance, a study examining the introduction of sheep by Norse settlers (Vikings) to the Faroe Islands of the North Atlantic concluded that, over time, the fine partitioning of land plots contributed more to soil erosion and degradation than grazing itself. The
Food and Agriculture Organization of the United Nations estimates that in coming decades, cropland will continue to be lost to industrial and
urban development, along with reclamation of wetlands, and conversion of forest to cultivation, resulting in the
loss of biodiversity and increased soil erosion.
Energy In modern agriculture, energy is used in on-farm mechanisation, food processing, storage, and transportation processes. It has therefore been found that energy prices are closely linked to
food prices. Oil is also used as an input in
agricultural chemicals. The
International Energy Agency projects higher prices of non-renewable energy resources as a result of fossil fuel resources being depleted. It may therefore decrease global
food security unless action is taken to 'decouple' fossil fuel energy from food production, with a move towards 'energy-smart' agricultural systems including
renewable energy. The use of solar powered irrigation in
Pakistan is said to be a closed system for agricultural water irrigation. The environmental cost of transportation could be avoided if people use local products.
Water In some areas sufficient
rainfall is available for crop growth, but many other areas require
irrigation. For irrigation systems to be sustainable, they require proper management (to avoid
salinization) and must not use more water from their source than is naturally replenishable. Otherwise, the water source effectively becomes a
non-renewable resource. Improvements in water
well drilling technology and
submersible pumps, combined with the development of
drip irrigation and low-pressure pivots, have made it possible to regularly achieve high crop yields in areas where reliance on rainfall alone had previously made successful agriculture unpredictable. However, this progress has come at a price. In many areas, such as the
Ogallala Aquifer, the water is being used faster than it can be replenished. According to the UC Davis Agricultural Sustainability Institute, several steps must be taken to develop drought-resistant farming systems even in "normal" years with average rainfall. These measures include both policy and management actions: • improving
water conservation and storage measures It is estimated that agricultural practices consume 69% of the world's fresh water. Farmers discovered a way to save water using wool in Wyoming and other parts of the United States. ==Social factors==