Timely Tips, July 2017
Mike Hubbs, Tennessee Association of Conservation Districts (TACD) Soil Health Specialist
Edited by Pat Turman and Greg Brann, NRCS
Infiltration is the process of water entering the soil. Infiltration rate is a measure of how fast water enters the soil. Water entering too slowly may lead to ponding on level fields or to erosion from surface runoff on sloping fields. Reducing erosion and runoff also reduce surface runoff of fertilizers and chemicals such as herbicides. Fertilizers and herbicides are agronomic inputs to assist farmers in producing productive and profitable yields. The objective of applying nutrients and herbicides and other chemicals are to benefit the plant. If the inputs runoff, it is a loss to the farmer and the environment.
Plants need water and sunshine to produce crop yield. Infiltration is dependent on soil type, soil organic matter and aggregate stability or soil structure. As farmers utilize conservation practices that increase soil organic matter, soil health indicators such as soil structure, aggregate stability, and infiltration will also improve.
Rainfall simulators have become quite common in Tennessee. NRCS uses them to demonstrate how cover crops, no-till, and good grazing practices improve infiltration and reduces erosion. Below is an example of rainfall simulator at Milan No-till Experiment Station on Soil Health Plots.
The five trays used were from five treatments left to right, no-till only, NT wheat only, NT cereal rye and crimson clover, NT five-way mix consisting of cereal rye, wheat, crimson clover, daikon radish, and purple top turnip, and NT cereal rye and vetch. Rainfall simulations were run multiple times totaling 3" of water. All trays had good soil structure due to long-term no-till. As you can see by the back jugs showing infiltration, the 5-way mix infiltrated the best.
In another demonstration, the picture below shows minimum tillage (it is still tillage),
no-till, over grazed pasture, conventional tillage tobacco with an excellent cover crop, and good grazing. Note that the good cover crop and the good grazed grass infiltrated and had little runoff compared to other treatments which had high runoff and poor infiltration.
So, all that is demonstration. Let’s put this to the test to real field conditions and real rainfall. Matt Griggs who is featured as the Number 3 in the Profiles of Soil Health Heroes on tnacd.org and also Matt Griggs update Profiles of Heroes. Matt recently sent me pictures in a rainstorm at his farm, true dedication
Cover crops add more carbon and increases soil biology that increases better aggregates which results in much greater soil structure, pore space, thus better infiltration rates. Pictures below show long-term no-till with standing water, four years plus of cover crops and no-till with great infiltration, and the bottom picture show where the two plots come together. A picture is worth a thousand words. Cover crops with no disturbances from tillage improve soil function, such as here, infiltration.
20 year No-till 2nd year with No-till with high biomass cover crop
No-till alone on the left and No-till with cover on the right
Soil health is improved by not disturbing the soil, keeping a root growing, keeping the soil covered, and diversity. The demonstrations and real farm application show continuous no-till with cover crops improve the soil’s ability to infiltrate water. Better water infiltration means better efficiency of water use and more stable yields.
Contact your local NRCS office for more information on improving soil health.
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