Abstract
Sustainability of vegetable farms in south Uruguay depends on development of farming systems that can arrest soil deterioration. In a context where major constraints exist for irrigation, and rainfall is highly spatial and temporally variable, one of the main causes of yield reduction in deteriorated soils might be the reduction in soil moisture supply capacity. We established an experiment to determine the effect of different tillage systems on soil water content, runoff and erosion at high rainfall intensity, and on processing tomato (Solanum esculentum) yield. We report the results of the first year of the experiment set up in march 2010 at a finesilty Pachic Argiudoll, with four treatments: Minimum Tillage with Cover Crop, planting oat (Avena byzantina) in basins and leaving it as mulch (MTCC); Conventional tillage with Green manure, same than previous treatment but oat biomass is incorporated to the soil through conventional tillage (CTGM); Conventional Tillage with Chicken Manure (CTChM); and Conventional Tillage (CT). Except CT, all other treatments incorporated chicken litter (7.0 Mg ha-1). Soil moisture was measured at 20 cm depth with time domain reflectrometry and at 100 cm depth with a neutron probe. Runoff and sediment loss were measured with a rainfall simulator at 6 mm/min rainfall intensity. Soil water content at 20 cm depth was the highest in the MTCC and lowest in CTGM and CTChM, yielding up to 10% more volume water content. Runoff and soil erosion was less at both treatments with oat, MTCC and CTGM. However, crop yield was the lowest at the MTCC, pointing out the need for extra attention to the fertilization scheme, because plants showed symptoms of N deficit at the beginning of the growth period. Minimum tillage with mulching contributed to conserve soil water, and to reduce soil runoff and soil erosion.
Highlights
Land degradation and poor soil fertility are major limitations to maintain vegetable production that makes an intensive use of the soil
The aim of this study was to test the hypothesis that tillage reduction with cover crops in conjunction with application of chicken litter in vegetable crops grown in raised beds on a fine textured soil, would improve soil moisture availability to plants while reducing runoff when compared to traditional technologies
Soil moisture Soil management, date, and their interaction had a significant effect on soil moisture at 20 cm depth
Summary
Land degradation and poor soil fertility are major limitations to maintain vegetable production that makes an intensive use of the soil. Many smallholder farmers in southern Uruguay have specialized and intensified their production systems in order to maintain their family income as production costs increase and vegetable prices are maintained or decrease. These changes have accelerated the soil degradation process mainly due to increased tillage intensity, poor soil cover, negative soil organic matter balance, and high frequency of the same crops [1]. Two projects at farm level aimed at re-design vegetable farm systems in southern Uruguay had as one of their pillars, the implementation of practices that could improve soil quality. The main practices implemented were: crop rotations, inclusion of a pasture phase when the farm size was big enough, incorporation of organic manures, and reducing plot sizes avoiding steep slopes
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