COS 26-9
High organic matter inputs result in increasing spatial and temporal stability of soil processes
Sustainable food production for a growing world population requires a healthy soil that can buffer environmental extremes and minimize its losses. There are currently two views on how to achieve this: by intensifying conventional agriculture or by developing organically based agriculture. It has been established that yields of conventional agriculture can be 20% higher than of organic agriculture. However, high yields of intensified conventional agriculture trade off with leaching of nutrients, loss of soil biodiversity and of ecosystem services. One of the key explanations for loss of nutrients and greenhouse gases from intensive agriculture is that these farming systems exhibit a high degree of temporal instability. However, little is known about how different agricultural practices affect spatial variation. In this study we compare the spatial variation of physical, chemical and biological parameters in a long term (13-year) field experiment with two conventional (low and medium organic matter input) and one organic farming system (high organic matter input). We evaluate the impact on ecosystem services that these farming systems provide.
Results/Conclusions
Soil chemical (N availability, N mineralization, pH) and soil biological parameters (nematode abundance, bacterial and fungal biomass) consistently show higher spatial variation under both conventional farming treatments than under organic farming. Average values for these parameters indicate a less consistent pattern. Under organic farming, values were higher for some parameters (pH, N mineralization) and lower for N availability, whereas biological parameters were not different between treatments. Higher variation in soil chemical and biological parameters coincides with the presence of ‘leaky’ spots (high nitrate leaching) in conventional farming systems, which shift unpredictably over the course of one season. In contrast, variation in soil physical factors (soil organic matter, soil aggregation, soil moisture) was similar between conventional and organic treatments. However, averages were higher under organic farming, indicating more buffered conditions for nutrient cycling that may underlie the observed reduction in spatial variation of soil chemical and biological parameters. Reduction in spatial variation correlates positively with a long-term increase in yield under organic farming with high organic matter input. Our study highlights the need for both policymakers and farmers alike to support farming that increases spatial stability.