As we come into early April it is important to take time to think about rangeland and pasture conditions and make sure grazing plans are ready for the growing season in 2024. Much of the state has seen close to normal precipitation since October first (current water year), however, parts of the state, especially counties in the south and east of the state, that experienced drought last summer are still experiencing drier than normal conditions.

Figure 1. ACIS Climate Map from the High Plains Climate Center showing percent of normal precipitation since October 1 for Nebraska as of March 26, 2024.

Soil moisture in the top three feet of the soil indicates water available for plants to utilize at the start of the growing season. White areas are considered near normal, while warm colors represent drier and cool colors wetter conditions (Figure 2).

Figure 2. Drought indicator based on satellite data showing moisture conditions in the top 3 feet of soil as of March 25, 2024. Data/maps available at nasagrace.unl.edu through a partnership with the National Drought Mitigation Center.

April and seasonal (spring/early summer) temperature and precipitation outlooks are looking favorable, currently predicted to the be normal, equal chances, or leaning above normal for April, May, and June for most of the state at this point (Figures 3 and 4).  

Figure 3. Map from NOAA Climate Prediction Center showing the probability of normal temperature and precipitation for the United States April 2024.

Figure 4. Map from NOAA Climate Prediction Center showing the probability of normal temperature and precipitation for the United States April through June 2024.

Pasture and native rangeland forage production fluctuates as the growing season progresses and is influenced by precipitation, temperature, range health, previous years precipitation and management, and soil nutrients. The amount and timing of spring and early summer precipitation is an important factor in determining annual forage production. Using trigger dates can help producers adjust stocking rates if precipitation, and the resulting forage production, is expected to be below average. Trigger dates will vary depending on the dominant forage.

Available soil moisture is a major diver of plant growth. Cool- and warm-season grass species have rapid-growth windows when optimum air temperature, day length, and soil moisture all are present for plants to fully express their growth potential. Once that window of opportunity has passed for a particular grass species, it is too late to get significant growth, even if it does rain. For example, cool-season grasses produce most of their growth in late spring and again in the fall, whereas warm-season grass growth occurs during the middle part of the growing season.

Precipitation during May, June and July are strongly correlated with total forage production of warm-season species and total forage production in the Nebraska Sandhills. In the Nebraska Panhandle, many range sites are dominated by cool-season grass plants, and forage production is influenced by April, May, and June precipitation. This same timeframe also applies to pastures dominated by smooth bromegrass; a cool season grass common in Eastern Nebraska. However, smooth bromegrass is a sod-forming grass and can be very drought-tolerant. Many smooth bromegrass pastures will grow again in the late summer and early fall when day length shortens and cooler nights return (Figure 5).

Areas affected by drought during the previous growing season will likely experience lower forage production even if adequate moisture is available this year. It is important to give range and pasture plants the chance to recover from drought and rebuild energy reserves. Maintaining a lower stocking rate post-drought can help accomplish this.

Figure 5. Annual growth curve of warm- and cool-season grasses. From NebGuide G1502, Perennial Forages for Irrigated Pastures

Suggested trigger dates

Trigger dates for an operation will depend on the grass species present and available grazing resources. Here are some key trigger dates to consider for Nebraska cool- and warm- season dominated range sites.

• April 1. Look at previous growing season precipitation and dormant season precipitation from October through March. Dig some post holes to see how much moisture is in the soil profile.  A lack of soil moisture in early April will impact growth from cool-season grass species such as Threadleaf sedge (blackroot) and Needlegrasses. Exceptionally dry conditions at this time can indicate the need to reduce stocking rates 10-20% on cool-season-dominated rangeland.
• April 15 to May 10. By this time, 30–45-day precipitation forecasts can have a moderate level of reliability. If above-average temperatures with average to below-average precipitation is predicted, plan additional reductions in stocking rates. In smooth bromegrass pastures with below-average precipitation, annual production may be reduced by 25-50%.
• May 20 to June 10. Needlegrasses will be completing their forage production and western wheatgrass is in its rapid growth window. If March-May precipitation was 50-75% of the long-term average, reduce stocking rates 30-40% or more depending upon grass species and plant health. Warm-season grasses such as prairie sandreed and little bluestem are just starting to grow.
• June 15 to June 30. Approximately 75 to 90% of grass growth on cool-season dominated range sites and 50% of grass growth on warm-season dominated range sites will have occurred.  Rainfall after late June usually has limited benefit for cool-season grass production but could still benefit warm-season grasses.

• June 15 to July 15. Precipitation and available soil moisture is critical for warm-season grass growth.

• July 15. Precipitation after this date will have limited benefit to warm-season tallgrass production but can still result in some forage growth from shortgrass warm-season species such as buffalograss and blue grama.

• September 1 to September 15. Smooth bromegrass or other cool-season-dominated pastures need adequate precipitation by these dates for enough fall forage growth to be grazed.

Resources

• The National Weather Service Climate Prediction Center provides short- and long-term precipitation and temperature forecasts.
• The NebGuide, Skillful Grazing Management on Semiarid Rangelands, describes the growth pattern of grass species and provides information on grazing management practices.
• The UNL Beef Team’s Drought Management Planning page provides a wide range of information related to drought including Managing Drought Risk on the Ranch from the National Drought Mitigation Center. This resource provides additional information on trigger dates and a planning guide.
• GrassCast is a forage forecasting software that uses remotely sensed data, past weather, and other information to give an estimate of expected forage production for the growing season.