Labor, soil quality, and yield in ecological and conventional small-scale, tropical agroecosystems

Background/Question/Methods

Sustainability of small-scale agriculture in the developing tropics is often difficult to achieve.  Ideally, sustainable management would simultaneously lower labor inputs, increase soil quality (SQ), and increase yields.  This study asks whether ecological or conventional management is more sustainable in the small-scale, tropical context.  A cross-sectional design with referral sampling was used during June-August 2006 in Leon, Nicaragua (tropical, deciduous climate) to answer this question.  All replicates were <10 manzanas (7 hectares), had andisols of sandy-loam texture, and planted late- season Sesamum indicum.  Measurements taken include labor and labor productivity, SQ and SQ efficiency, and Sesamum yield.  A management index identified the approach to overall agroecosystem management on a scale from conventional to ecological.  A semi- structured interview was employed in gathering labor and yield data.  Soil sampling and indicator analysis measured soil quality.  SQ indicators included percent organic matter, acidity, phosphorus availability, biotic activity, and bulk density at two depths.  T-tests and Mann- Whitney were used to test for differences between the two groups. 

Results/Conclusions

Total labor was not affected by management approach, nor was labor productivity.  Labor amounts (man-days/Mz) differed significantly only for fertilization (p<.05) and disease control (p<.10) practices, with ecological management requiring more labor.  Conventional farmers allotted greater proportions of their labor to weed (p<.10) and insect pest (p<.10) control than did ecological farmers.  Labor productivity was not different between treatments for any practices or in totality, though very small sample sizes lowers confidence in these results.  Results indicate that where techniques are different, ecological approaches often require more labor.  Insect pest control is the exception.  Where techniques are similar, labor requirements will likely not differ.  No soil quality indicator or efficiency was significantly affected by management regime.  Therefore, in most respects, ecological sustainability did not change with management.  This contrasts with most studies to date.  Yield was also unaffected by management approach, indicating that ecologically managed systems do not necessarily yield less.  Given all this, neither agroecosystem seems to be more sustainable.  This may be due to similar inputs between all small-scale systems, regardless of management type.