Soil health impact on biodiversity.


Soil is a crucial component of biodiversity. Its microbial diversity, including bacteria, fungi, protozoa, and algae, is vital for nutrient cycling, organic matter decomposition, and soil structure formation. High microbial diversity supports ecosystem functions and resilience against diseases. Soil fauna, such as nematodes, earthworms, mites, and insects, aerate the soil and enhance nutrient availability for plants. Additionally, plants rely on symbiotic relationships with soil organisms, like mycorrhizal fungi, which help them absorb water and nutrients. Being a complex system, soil supports diverse communities of micro-organisms, plants, and animals, contributing to the efficient function of ecosystems and landscapes. 

Cotton farming has a significant impact on soil health. Organic farming practices promote soil health and biodiversity due to the absence of pesticides and synthetic fertilizers, while conventional farming has a considerable impact. Unsustainable cotton practices, such as monoculture farming, misuse of pesticides and fertilizers, lack of soil management, use of heavy machinery, and insufficient irrigation, lead to soil damage and loss of biodiversity. 

Erosion is caused by factors such as the percentage of soil covered with a crop, the angle of the field surface, type of irrigation and rainfall pattern, soil type, and measures taken. Conventional farming involving frequent tillage and the removal of plant cover makes soil more vulnerable to wind and water erosion, leading to the loss of topsoil rich in nutrition and organic matter. While there was rapid adoption of no-till technologies from 1990 to 2010, the share of no-till cotton has remained steady at around 18% over the past decade, with a further 20% grown using reduced tillage and the remaining 60% still using conventional tillage, according to Fieldtomarket. 

As a nutrient-intensive crop in terms of nitrogen, phosphorus, and potassium, improper farming without established fertilizing management leads to soil fertility degradation due to nutrient depletion. Fertilizers are applied for this reason. One disadvantage of using animal manure as a primary source of nitrogen is that organic nitrogen must first decompose microbially to ammonium and nitrate before it can be taken up by plants. Synthetic fertilizer can be taken up instantaneously by a plant, and if applied according to the plant’s needs, virtually no fertilizer will be lost to the environment. However, much energy is needed for the production of nitrate and ammonium, contributing to global warming. Mining phosphorus and potassium may cause environmental impacts, including changes in the landscape, water contamination, excessive water consumption, and air pollution (Kooistra et al., 2006). Inadequate fertilization impacts the ecosystem balance, leading to shifts in biodiversity. 

The use of heavy machinery in larger farms compacts the soil, reducing pore space, affecting water infiltration, root growth, and soil aeration. Soil with lower permeability and reduced biological activities results from such compaction. 

Salinization is another risk factor, particularly in areas with poor irrigation management. Excessive irrigation and inadequate drainage cause salt accumulation in the soil, making it less fertile and leading to the loss of vegetation and organisms. Soil salinization occurs when evapotranspiration exceeds rainfall, posing a threat to irrigated areas in particular. Irrigation water dissolves calcium carbonate and soluble salts in the soil. Since calcium carbonate is relatively insoluble, it accumulates in the topsoil, leading to additional salt deposition (originating from the irrigation water) and waterlogging. Soil salinization may also occur when the groundwater of land near a sea is overused. In the twelve leading cotton-producing countries, an estimated 12-36% of the area under cotton cultivation is affected to some degree by salinization. In Uzbekistan, 44% of the land is now unproductive due to salinization. Current estimates for salinization-affected cotton areas are as follows: for India, 27-60% of the irrigated land; for Pakistan, 14%; for Israel, 13%; for Australia, 20%; for China, 15%; for Iraq, 50%; and for Egypt, 30% (Kooistra et al., 2006).