Database results:
examBoard: Cambridge
examType: IGCSE
lessonTitle: Organic Fertilisers: Crop Residue and Manure
Organic fertilisers are natural materials derived from plants, animals, or minerals that provide essential nutrients to crops while improving soil health. Unlike synthetic fertilisers, organic options work with natural soil processes and contribute to sustainable farming practices.
Key Definitions:
Organic fertilisers play a crucial role in sustainable agriculture by recycling nutrients, building soil structure and reducing chemical inputs. They help create farming systems that can maintain productivity while protecting the environment for future generations.
Organic fertilisers provide macronutrients (nitrogen, phosphorus, potassium) and micronutrients that plants need. They release these nutrients slowly, matching plant uptake rates and reducing nutrient runoff that can pollute waterways.
Crop residue refers to the plant material left in fields after harvesting. Instead of burning or removing these materials, farmers can incorporate them back into the soil as valuable organic fertiliser.
Different crops produce various types of residue, each with unique properties and nutrient contents:
Wheat, rice and corn stalks are high in carbon but lower in nitrogen. They decompose slowly and help build soil structure over time.
Bean, pea and clover residues are nitrogen-rich due to nitrogen fixation. They decompose quickly and provide readily available nutrients.
Potato and carrot tops contain balanced nutrients and break down at a moderate rate, improving soil aggregation.
Incorporating crop residues into agricultural systems offers multiple advantages for soil health and farm sustainability:
Farmers in Zambia have adopted conservation agriculture practices that include retaining crop residues on fields. This approach has increased maize yields by 30-50% while reducing erosion by up to 75%. The residues protect soil during heavy rains and gradually release nutrients as they decompose, creating a more resilient farming system.
Animal manure has been used as fertiliser for thousands of years. It contains valuable plant nutrients and organic matter that can significantly improve soil fertility and structure.
Different animal manures have varying nutrient compositions and characteristics:
Balanced nutrient content with moderate nitrogen levels. Decomposes slowly and builds soil organic matter. Contains about 0.5% N, 0.2% P, 0.5% K.
High in nitrogen and phosphorus. Breaks down quickly and provides rapid nutrient release. Contains about 1.5% N, 1.0% P, 0.5% K.
Higher nutrient concentration than cattle manure. Pellet form makes it easy to apply. Contains about 0.7% N, 0.3% P, 0.9% K.
To maximise benefits and minimise risks, manure must be properly managed before and during application:
Composting manure before application kills pathogens, reduces odour and creates a more stable product. The process involves piling manure with carbon-rich materials and allowing it to heat up through microbial activity. Properly composted manure is safer to handle and less likely to burn plants.
Apply manure when crops can use the nutrients typically before planting or during early growth stages. Avoid application before heavy rains to prevent runoff. For most crops, spring application works best as it provides nutrients when plants need them most.
While manure is beneficial, improper management can lead to environmental problems:
In rural India, many farmers use biogas digesters to process cattle manure. This system captures methane (a potent greenhouse gas) for cooking fuel while producing nutrient-rich slurry as a by-product. The slurry is an excellent organic fertiliser that has helped farmers reduce chemical fertiliser use by up to 50% while maintaining crop yields. This approach addresses both energy needs and soil fertility in a sustainable cycle.
Crop residues and animal manures work well together in farming systems. Residues are typically high in carbon but lower in nutrients, while manures provide more readily available nutrients. Using both creates a balanced approach to soil fertility management that builds organic matter while meeting crop nutrient needs.
Availability often determines which organic fertiliser farmers use. Crop residues are readily available on-farm, while manure may need to be transported if the farm doesn't have livestock. Cost, labour requirements and equipment needs also influence farmers' choices between these organic fertiliser options.
To get the most benefit from organic fertilisers while minimising potential problems:
Farmers using organic fertilisers face several challenges:
As agriculture faces challenges from climate change and resource limitations, organic fertilisers are becoming increasingly important. Research is improving our understanding of how to optimise their use and new technologies are making application more efficient. Policies supporting sustainable agriculture are also encouraging more farmers to adopt organic fertiliser use as part of integrated nutrient management strategies.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.