Carbon footprint and nutrient bio-availability assessment of organic systems

Cornelius Adesanmi Adewale

Assessing the (i) carbon footprint (CF) and (ii) nutrient availability and fertilizer needs of organic farming systems can help inform organic farmers about the sustainability of their management practices. Despite the various greenhouse gases (GHG) mitigation potentials embedded in organic farming principles, a full accounting and understanding of GHG emissions associated with specific activities, materials, and energy in organic operations are needed. A small-scale organic vegetable farm in the Washington State, USA, was used as a case study to determine GHG hotspot areas that could help in decision- making for GHG mitigation. Accounting was done using a partial life cycle assessment to identify primary and secondary GHG sources and sinks associated with producing potatoes, cauliflower, dry bus beans, winter squash, summer squash, chard, peppers, and onions. Fuel and energy use, fertilization, and plastic-based materials for pest management were identified as the major GHG hotspots on the farm. This study also identified production of potato, pepper, and cauliflower as hotspots in the farm rotation. Optimizing or finding alternatives for the use of plastic-based materials for v pepper and cauliflower production and peat for greenhouse operations could reduce the farm’s CF. Estimating soil nutrient availability and fertilizer needs in conventional and organic cropping systems is mostly based on interpreting soil analyses by chemical extraction (CE). However, fertility management in organic systems relies more on organic matter and biological processes than in conventional systems. Increasingly, ion exchange membranes (IEMs) are used as an alternative measure of nutrient availability. But estimates of nutrient availability and fertilizer needs based on IEM and CE have rarely been compared, particularly for organically managed soils. Using soil samples from five organic farms, a second study examined the variability and correlation between nutrient availability estimates and fertilizer recommendations based on CE and IEM. This study found a significant difference using CE and IEM methods for N and P fertilizer recommendations, and in assessing soil N and P status in organically managed soils. Further research is needed in correlating CE and IEM results to nutrient uptake and yield response, and calibrating those responses to fertilizer recommendations for organically managed soils.

Carbon footprint and nutrient bio-availability assessment of organic systems

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