Essay: written by student Charlotte
Discuss ways in which farmers may control the environment of crop plants and animals to increase productivity/maximise crop yields
To capitalise on the productivity of plants and animals in an agricultural environment there are several steps which a farmer can take to improve growing conditions and therefore yield. By providing optimum conditions for growth factors such as temperature and nutrient supply and limiting potential competition, the productivity of the land can be dramatically improved.
Initially, the physical condition of the soil can be modified to improve growth of crop plants. By maintaining a neutral soil pH, farmers can ensure that nutrients contained in the soil are not lost if the soil were to become acidic. Acidic soils limit plant growth because large concentrations of hydrogen ions in the soil displace micro- and macro-nutrient ions, such as K+, held by electrostatic charge to clay particles. The displacement of these nutrient ions leaves them free in soil, in other words more soluble, and so they are then leached out, leaving soils depleted of nutrients. Acidic soils are formed by acid rain or water-logging of soils, which encourages anaerobic bacteria which produce carbon dioxide which dissolves in solution to form carbonic acid. To raise the pH of the soil making it less acidic, land can also be rotivated to improve drainage or lime can be added to the soil, thus restoring the preferred pH of about pH 7.
In addition to maintaining the soil pH, nutrients can also be added in the form of inorganic or organic fertilisers. Fertilisers are applied to promote plant growth; the main nutrients present in fertilisers are nitrogen, phosphorus and potassium, (the macronutrients) and other nutrients, micronutrients, are added in smaller amounts. Fertilizers are usually directly applied to soil, and can also be sprayed on leaves. As some crops, such as wheat, need a higher level of specific nutrients – in this case wheat needs more nitrogen – these nutrients can be added in addition to any nutrients found in the soil to improve overall supply. Organic fertilisers are from natural resources such as farm yard manure and inorganic fertilisers are made by Haber process. Two other methods of improving soil fertility are crop rotation and green manure. Green manure involves ploughing in a crop such as grass or rye, or a leguminous plant such as clover which is nitrogen fixing, or leaving the previous crop in the soil so that organic material is returned to the soil. Crop rotations have two major benefits, changing the crops allows organic nutrient levels to be restored e.g. by replacing a high nitrogen demand plant with a leguminous plant which is nitrogen fixing to replenish nitrogen levels. The other major benefit of crop rotation is that it breaks the pest life cycles and so helps reduce the damage and lower yields caused by pests which would also aid plant growth.
Irrigation is another crucial fact...
