How much rain fell on a field — and how much moisture remains in the soil — can influence some of the most important management decisions producers make during the growing season.
Making those decisions requires timely information about field conditions, including soil water content and fertility. When soil water is limited, for example, producers may need to consider irrigation where it is available. Estimating soil water content requires information about recent rainfall and how much water a crop, such as corn or soybean, is using at its current growth stage.
To assist this decision-making process, Nebraska Extension Agricultural Climatologist Steve Hu and Nebraska Extension Irrigated Cropping Systems Extension Educator Steve Melvin have developed a new web resource for producers: Weather and Climate Information for Agricultural Decision-Making. The site provides accumulated precipitation estimates for the previous 24, 48 and 72 hours at a resolution — or level of geographic detail — of 4 kilometers (2.48 miles). While the 4-kilometer resolution is less detailed than the ideal resolution of less than a mile, it provides producers with information they can use to estimate recent rainfall on their crops. In addition, the site provides examples of how to estimate rainfall totals at any location across Nebraska.
Alongside rainfall, the site has a page displaying calculated soil moisture for the previous day and previous month. The calculated soil moisture represents the amount of water in the crop rooting zone, expressed in millimeters, either for the previous day or as an average for the previous month. The maps also show how current soil moisture compares with the 1991–2020 average, helping users identify areas that are wetter or drier than normal.
One limitation of the map is its lower resolution. Because it covers the contiguous U.S., it may not capture localized differences in soil moisture, which can vary substantially over short distances due to topography, soil type and crop or vegetation cover. Nonetheless, the calculated soil moisture provides an indication of background soil water conditions across the state.
Because it can take a long time — sometimes weeks to a month — for soil moisture to go through considerable changes, tracking background soil moisture condition can guide decisions for irrigation and chemical application timing.
In addition, the site provides the net gain or loss of soil water at locations over the past week or month. The net gain or loss is calculated by subtracting evaporated surface water from precipitation. When precipitation exceeds evaporation, the result is a net water gain; when evaporation exceeds precipitation, it indicates a net loss.
Combined with current soil moisture information, these data can help producers understand whether soil water conditions are improving or declining — an essential element in making management decisions throughout the growing season.
Unlike many online weather data sources, this resource is supported by Nebraska Extension faculty who can help producers interpret the information and apply it to different landscapes and cropping systems. The site will continue to be updated and improved based on producer needs, with the goal of helping users build confidence in applying weather and climate information to management decisions on their operations.
