Potato Irrigation: Computing the Available Water Individually for Each Layer of a Soil Profile

The amount and quality of potato crop yield are significantly influenced by the availability of soil water. When an infection has already occurred, insufficient water can worsen common scab or Verticillium Wilt, reduce yields, or cause tuber malformations.
Inadequate or over-watering crops can lead to several disease issues in the field or during storage, reduce yields and quality, and remove nutrients from the root zone. Variations in the availability of water are favorable to conditions like sugar ends, hollow hearts, and brown centers or second growth.
Determining the soil’s water-holding capacity is necessary for effective irrigation. The amount of soil water that plants can extract is known as available water. When a specific percentage of the available water, known as the allowable depletion, has been used during the growing season, irrigation becomes necessary. The permissible depletion in a given field varies based on the type of soil, crop growth stage, water availability, climate, and cost of irrigation. Potatoes can only tolerate a maximum depletion of 30 to 40% because they are susceptible to water stress. At tuber initiation, a maximum depletion of 20% is permissible to reduce common scab infection.
Potatoes are a shallow-rooted crop, having 90% of the roots growing in the first 12 to 18 inches of soil. A potato producer can assess how much accessible water the soil can store based on the clay concentration and soil texture in the first 18 inches. Farmers should compute the available water individually for each layer of a soil profile that comprises distinct soil types, and then combine them to get the total available water in the rooting zone. Growers should consider salinity when predicting available water; if the soil or irrigation water includes high amounts of salt, plants will withdraw less water, resulting in less accessible water.
The Efficiency of the Different Methods of Irrigation
Potato fields are commonly irrigated using four methods: overhead rain guns, boom irrigation, sprinkler systems, and drip irrigation.
The primary application technique is via overhead rain guns, which are cheap and adaptable. Although they can be effective, their uneven application might cause over-watering in some places. Proper control over pressure, nozzle size, and gun angle is necessary to accommodate changing application circumstances.
Boom irrigation increases water application consistency, which is beneficial for controlling scab. However, its usage may be limited because of the soil type, terrain, layout, and “field furniture.” Excessive application rates can cause ridge erosion, soil slumping, and runoff.
Sprinkler systems are more expensive initially but offer better consistency, more frequent application of tiny dosages, and a reduction in manpower requirements over the season. Structural damage is prevented from sensitive soils.
You can read the rest of this article in your complimentary e-copy of Issue 2 of Potato Business Digital 2024 magazine, which you can access by clicking here.