Analysis of differences in productivity, profitability and soil fertility between organic and conventional cropping systems in the (sub)tropics

Organic farming, which aims at increasing soil fertility by avoiding synthetic inputs and using locally available natural resources, is regarded as a sustainable alternative to conventional farming because it ensures higher biodiversity, restricts environmental pollution, prevents land degradation and is easy to apply for smallholder and subsistence farmers. Although widely applied and investigated in temperate regions, only little is known about organic farming in the tropics and subtropics. This research tries to fill this gap by making an analysis of the differences between organic and conventional agriculture in this region based on an extensive literature research including 88 papers (with 458 data pairs). This comparison is focussed around three main indicators: yield, gross margin and soil organic carbon (SOC); and uses ratios and different statistical models to analyse these differences. The results demonstrate that in organic systems, yields are on average 26% higher, gross margins are 39% higher and SOC is 53% higher compared to conventional systems. Organic farming achieves highest yield increases in the least developed countries, in arid regions, on coarse soils and in systems that previously had low (synthetic) inputs. The time after conversion and the development of a country are the most important determinants for the differences in organic and conventional yields. For gross margins, certification best explains the differences between organic and conventional systems. Certified farmers, mostly located in developed countries, receive significantly higher prices. Furthermore, the driest regions achieve significantly higher profits than other regions. Results for SOC are not clear-cut, but suggest highest increases in systems that used to have high inputs, in regions with 1000-1500 mm of rainfall and on clayey soils. This study demonstrates that organic farming is a viable alternative to conventional farming in the (sub)tropics and should especially be further developed in driest and poorest regions, where higher yields could lead to enhanced food security and increased prosperity. Initiating certification in these regions can help farmers to achieve higher profits. Carbon sequestration on the other hand, seems most effective outside these regions, but would need further investigation. Also the ability of organic farming to provide sufficient nutrients on longer terms and bigger scales needs further research