FURROW IRRIGATION INFILTRATION WITH MULTIPLE TRAFFIC AND INCREASED AXLE MASS

Abstract

Pullman clay loam and related soils in the Southern High Plains are slowly to moderately permeable, and furrow wheel traffic reduces irrigation infiltration rates. Traffic effects were evaluated with treatments of one (1) and two (2) furrow passes with relatively light (L) and heavy (H) tractors of 4.1 and 8.2 Mg (9,000 and 18,000 lb) mass, respectively, having 75% of the mass on the rear axle. Treatments are designated L-1, L-2, H-1, and H-2. Both larger tractor mass and repeated traffic increased tillage zone compaction and reduced irrigation infiltration rates and total infiltration. Soil strength (cone penetrometer) from wheel traffic compaction was greatest at the 100 to 150 mm (4 to 6 in.) depth for all treatments, which is near the bottom of the 150 m (6 in.) primary tillage zone. For the first 8-h infiltration test after tillage, using a flowing furrow infiltrometer, the L-1, L-2, H-1, and H-2 treatments reduced average infiltration by 23, 33, 38, and 43%, respectively; compared with 212 mm (8.3 in.) of infiltration for the no-traffic check. Because of furrow surface layer consolidation after the first irrigation, infiltration for all treatments was about 20% less during the second tests about 60 days later. The check infiltrated 171 mm (7.3 in.) and traffic induced infiltration reductions were 16, 23, 28, and 36%, respectively, for L-1, L-2, H-1, and H-2 treatments. A better understanding of variable furrow traffic effects on irrigation infiltration enables producers to improve water application efficiency by using traffic compaction to reduce excessive early season infiltration or by limiting traffic where low infiltration is a concern later in a crop season.