Assessing the Benefits of Organic Fertilizers in Cropping Systems

Soil is a vital carbon sink that sustains life on Earth. However, human activities, such as agricultural practices involving inorganic fertilizer use, can negatively affect soil health. In Australia, most cropping soils have lost 2-3% of their nitrogen reserves annually and are low in phosphorus. Potassium levels are also low or deficient on many sandy soils, and can be depleted due to intensive grazing and horticulture. Organic fertilizers, which are derived from organic waste materials, can offer a sustainable solution by improving soil structure, increasing soil carbon storage and other co-benefits. This can lead to sustain or higher crop yields, improved farm profitability and help to mitigate climate change.

This paper identifies potential organic fertilizers that farmers can use, and assesses their impacts on crop yields, soil health, and greenhouse gas emissions. Based on this assessment, it can develop guidelines for farmers on how to incorporate organic fertilizers into their cropping systems and improve farm income. This initiative has the potential to make a significant contribution to the sustainability and profitability of Australian agriculture. By improving soil health and reducing greenhouse gas emissions, organic fertilizers can help farmers to produce more food with less environmental impact.

Organic amendments, such as biochar, farmyard manure, animal manure, and chicken manure, are increasingly being used in cropping systems to improve soil health and crop yields. However, their impact is complex and depends on a variety of factors, in particular their economic feasibility to use and the level of any risk involved. To better understand this impact, we used the Agriculture Production System Simulator (APSIM) model to selected organic amendments. APSIM simulates crop growth, soil water movement, and nutrient cycling. To simulate organic amendments in APSIM, we need parameters such as the fraction of carbon in fresh organic matter, the potential decomposition rate, and the fraction of C, N, and P in the amendment. We obtained these parameters from published literature or laboratory experiments.

Our results show that organic, as combined with inorganic fertilizers, could be used as substitutes for nitrogen mineral fertilizers in growing crops, as these treatments sustained productivity while improving soil health. Our analysis also showed that biochar has a larger impact on environmental outcomes than farmyard manure in the case study area used in our analysis. To provide some perspective on the trends of economic and environmental trade-offs, we present some economic model concepts. This work will provide a better understanding of the impact of organic amendments on crop yields, nutrient uptake, soil health and farm income.