|Pikul jr, Joseph|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/28/2002
Publication Date: 5/1/2003
Citation: PIKUL JR, J.L., AASE, J.K. WATER INFILTRATION AND STORAGE AFFECTED BY SUBSOILING AND SUBSEQUENT TILLAGE. SOIL SCIENCE SOCIETY OF AMERICA JOURNAL. 2003. Vol. 67 (3) p. 859-866. Interpretive Summary: In this study we have shown that water infiltration was improved by subsoiling, but secondary tillage destroyed vertical continuity of macropore channels resulting in reduced water infiltration. Our hypothesis was that tillage induced soil macropores provide important preferential flow paths through slowly permeable soil layers and thereby increase water infiltration. These soils have little structure and are susceptible to surface crusting, even with artificial rainfall that was less intense than naturally occurring storms. Smooth surface conditions following secondary disk tillage or sweep tillage were a detriment to water infiltration because the surface rapidly slaked during the first of three artificial rainstorms. Results show a difficult soil management problem. Subsoil tillage improves water infiltration, but benefits of subsoiling on water infiltration were reduced by secondary tillage. Further, no additional water storage was discernable in any treatment after a short time. There is an upper limit to the quantity of water that can be stored in this soil. Water in excess of this upper limit percolates and carries water-soluble nutrients (like nitrate-N) out of the root zone. Nutrient leaching is an inherent problem in this area and represents a risk to ground water quality. Annual cropping, rather than crop-fallow, is an effective soil-water-management tool because the crop utilizes growing season precipitation as it comes, and consequently, reduces the potential for deep leaching of nutrients.
Technical Abstract: Potential benefits of subsoiling are difficult to predict. Objectives were to determine effect of subsoiling on water infiltration/storage and evaluate longevity of soil structure following tillage. Tillage treatments were no subsoiling (NoSS), subsoiled (SS), and subsoiled plus secondary tillage (SSplus). Soils were Dooley fine sandy loam (Exp 1) and Williams loam (Exp 2). Subsoiling (0.3 m deep) in Exp 1 was with a paratill and with parabolic subsoiling shanks in Exp 2. Secondary tillage (0.1 m deep) was with a disk (Exp 1) and with sweeps (Exp 2). Infiltration was measured using a sprinkler infiltrometer. Average final infiltration rate, after 2 simulated storms, was 14 mm/h on NoSS, 29 mm/h on SS, and 7 mm/h on SSplus. Penetration resistance measurements show that soil subsidence following simulated rainstorms was less on treatments with no secondary tillage. Average water drainage (1.83 m profile) was 1.4 mm/h during the first 3 days after water application. Subsequent drainage was 0.23 mm/h (days 3 to 7) and 0.09 mm/h (days 7 to 15). Soil profiles drained to about 444 mm of water in 15 days on all treatments. Results reveal a difficult soil management problem. Subsoiling initially improves water infiltration however, any gains in water storage were lost to deep drainage within 15 days. Excessive water infiltration and deep percolation of that water may represent a risk to ground water quality because soluble fertilizer salts, like nitrate-N, can be leached out of the root zone.