Human changes: Farming practices

Question 1

Overview

Answer 1

Ploughing and harvesting, rearing livestock, using machinery and using artificial fertilisers are all farming practices that release carbon.

Question 2

Cattle and rice

Answer 2

Livestock, especially cattle ruminate (regurgitate food and masticate a second time- ‘chewing the cud’) which produces methane as a by-product. Cattle in the USA emit around 5.5 million tonnes of methane per year into the atmosphere (around 20% of total methane emissions in the USA). This has raised issues about the desirability of moving away from such a high dependence on meat and dairy products.

Methane is also produced in rice cultivation. Rice may contribute 20% to global methane production. As rice is the primary food source for 50% of the world’s population, mostly in developing regions, this is likely to continue

Livestock alter ground cover by soil compaction and erosion, thus altering nutrient cycles and runoff.

Question 3

farming practices

Answer 3

Tillage (preparing of land using machinery) increases the aeration of the soil and soil temperatures, making soil aggregates more susceptible to breakdown and organic matter more available for decomposition.

Ploughing inverts soil layers so air mixes in and soil microbial activity increases. This leads to soil organic matter being broken down more rapidly. Carbon is lost from soil to the atmosphere.

Emissions from tractors increase CO2 levels in the atmosphere. Intensive use of artificial fertilisers can lead to soils becoming sterile with loss of their organic content. According to the United Nations Food and Agriculture Organization (FAO), in 2011, 44% of agricultural-related greenhouse gas outputs occurred in Asia, followed by 25% in the Americas.