Summary
This site had been studied from 2004 until 2008. The location comprises 4 plots of 300 m2. Landscape is formed by gentle hills, with mainly moderate slope (10%) and corresponds mainly to the outside walls of the Atecuaro volcanic caldera of 13M years old. The presence of gullies is exceptional, because it is sheet erosion which occurs and the small rills disappear after every field works. Land used is for half part forest and half part fields, with one year corn alone and the other year fallow. Nevertheless, since the opening of the US market for the avocadoes, there is a lot of avocado plantations since the last 3 years which can produced strong erosion if precautions are not done.
SWC tested include improvement of fertility, increasing of permeability, reducing of soil erosion, mulching, and increase of field production for man as well for animal. Plots are under 4 different agronomical treatments based on the traditional crop association of maize without association and fallow: Fallow, traditional crop, zero tillage+crop residues, and crop with improved fertility (chemical + crop residues). In year 4 and 5 the improved fertility treatment had been replaced by barley crop. Ploughing direction is normal. Plots are delimitated by small earth wall and a H-flume downstream conduce runoff and sediments eroded to tanks of 100 l capacity. In case of higher runoff volume, a nearly 2% of water quantity is retain in a second tank. Water with sediments was sampled after every events (means nearly every day during rainy season). Water was analyzed (N, P, K, C) as well as sediments if this quantity allow it (rare cases). On fields, soil water contents (Watermark tensiometers) at 5, 15, 30, 50 and 80 cm deep was followed daily, roughness (roughness meter during year 1 and 2 then chain) and soil cover (photo+GIS) after every heavy rain. In year 5, samples to measure aggregate stability had been done. Field production was measured too. Meteo variables are measured every 30 mn (except rain every seconds during rain event) in place.
