Nitrogen and phosphorus are essential nutrients for plant growth and is cycled through agricultural and horticultural practices and natural processes. Here's an outline of these processes on farms:
Fertilizer Application: Farmers apply nitrogen and phosphorus-rich fertilizers to fields to supplement soil fertility and enhance plant growth.
Animal Manure: Livestock waste contains organic phosphorus and nitrogen. When applied to fields as manure, this becomes available to plants after decomposition.
Runoff and Erosion: Rainwater can wash away excess phosphorus and nitrates from fields, carrying it into nearby water bodies through runoff. Soil erosion can also transport phosphorus and nitrates from fields to waterways. In aquatic ecosystems, excessive phosphorus and nitrogen can promote the growth of algae blooms.
Algal Growth: Algae blooms deplete oxygen levels in waterways, potentially harming aquatic ecosystems in a process called eutrophication.
Plant Harvest and Consumption: When crops are harvested, nitrogen and phosphorus is removed from fields which requires replacement through application of fertilizers.
Crop Rotation and Cover Crops: Farmers may use crop rotation and cover crops to manage nitrogen and phosphorus levels in the soil, prevent nutrient depletion, and reduce the need for excessive fertilization.
Efficiency and Environmental Impact: Efficient fertiliser management is important to minimize nutrient loss, which can lead to air and water pollution, including the formation of greenhouse gases and eutrophication in water bodies.
Balancing nitrogen and phosphorus inputs, plant needs, and environmental impacts is crucial in sustainable farming practices. Proper management can enhance crop productivity while minimizing negative effects on surrounding ecosystems.
Balanced nutrient management aims to optimize agricultural productivity while safeguarding the environment and maintaining long-term soil health. Customizing strategies to specific farm conditions and local ecosystems is crucial for sustainable nutrient management.
Nutrients are naturally found in the soil. Some land management practices can lead to excessive loss of nutrients to waterways. Increased nutrients in waterways encourages algal growth, deteriorate water quality, and renders it unfit for drinking and recreational use. Land management practices have improved significantly over time, to reduce the loss of nutrients from the soil. Nutrients are vital for plant growth and have a fertiliser value. Holding onto them in the soil is the best outcome economically and environmentally.
Sites at risk of losing containments, typically bacteria, sediment, phosphorus, and nitrogen, are considered critical source areas (CSAs). Managing these sites can reduce the amount of topsoil loss and containments in waterways. DairyNZ's critical source areas page outlines the potential management options that could be implemented to manage CSAs.