SOIL-WATER BASICS & SOIL HEALTH


Compost spread over sandy soil, as shown here, helps with the water holding capacity and supports forage crop production.


California Department of Food and Agriculture Healthy Soils Program.


WHILE MANAGEMENT CANNOT CHANGE SOIL TEXTURE, WATER INFILTRATION AND RETENTION CAN BE IMPROVED BY BUILDING SOIL ORGANIC MATTER AND SOIL STRUCTURE.


Cover crops are grown during fallow periods in annual crops, while they are planted in the drive rows between the trees or vines in perennial crops. Cover crops add organic matter to the soil, promote soil aggregation and create large soil pores, supporting improved drainage and infiltration. When choosing cover crop mixes with legumes, cover crops also add nitrogen to the soil. To avoid competition for water between the cover crop and the cash crop, cover crops can be terminated through mowing or incorporated at the end of the rainy season.


Compost is one of the most common amendments to improve soil health. Upon soil application, compost serves as a food source for soil organisms and contributes to building aggregates and soil organic matter. The impact of compost application on infiltration and water retention depends on the


22 Irrigation TODAY | Winter 2022


number of years compost has been applied, the rate of compost application, as well as the feedstock and compost processing techniques. In arid regions, compost quality should be assessed carefully with regard to salt content. Some compost sources can have a relatively high salt content, potentially invoking increased drought stress in the crop.


Reducing tillage intensity to improve infiltration often seems contradictory. Tillage opens up the soil, which in turn promotes fast water infiltration shortly following tillage. However, tillage is known to break up aggregates. Without sufficient aggregation, the openings in the soil surface will quickly close up in response to precipitation and irrigation. Early in the season, tillage may increase infiltration, but this pattern is often reversed as the season progresses. Completely eliminating tillage may not be possible or suitable for all cropping systems, but strategically planning tillage intensity can help maintain or build a level of soil structure that supports improved


irrigationtoday.org


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40