Fields and Homegardens (representative of tropical smallholder extensive and intensive systems) were
compared for soil quality and productivity of maize and mungbean in a hilly region of Sri Lanka (twinned
30 farms with Fields and Homegardens, each) over 2 years. The inclination categories were Flat (0–10%),
Moderate (10–30%) and Steep (>30%). On half of the farms, green manure was added using Gliricidia leaves
(3 tonnes ha−1 per season). Soil organic matter contents of Homegardens were at least 30% greater than in
Fields, most pronounced in the Flat category. After 2 years of continuous maize and mungbean cropping
in the major and minor rainy seasons, respectively, SOM generally declined; the greater depletion rate
in Homegardens was positively correlated with crop yields. With recommended fertilizers (NPK), maize
yield was always significantly higher in Homegardens than in Fields Flat and Moderate, this hold true
at Steep lands only without NPK. Maize yield with NPK was on average two times higher than with
Gliricidia alone, a respectable 4.5 tonnes ha−1 at Flat and Moderate, and 3.5 tonnes ha−1 even on Steep
lands, seemingly the chemical soil fertility was more lacking than the physical properties. Gliricidia
alone had no impact on yield in Fields but just in Homegardens, yield was increased by almost 30% in
comparison to Zero fertilizer, an indication that chemical fertility was not directly supported by Gliricidia.
Mungbean yields were generally less influenced by treatments, just the beneficial short term impacts
of Gliricidia in Fields were relatively much higher than in maize. Conclusively, the long term input of
organic manure in Homegardens was translated into a higher productivity in comparison to extensively
managed Fields. However, the annual green manure supply supported yields mostly at marginal input
levels and was overridden by mineral fertilizers independent of the inclination. Although, the usefulness
of Gliricidia in degraded Steep lands was proven, the great risk of erosion remains in this landscape. Arable
cropping there should be replaced by access to NPK on low inclined land once socio-economic conditions
allow it.