By Aaron Berger
Warm, windy and dry conditions in March have dried out the topsoil in parts of Nebraska. While adequate subsoil moisture still exists in many locations, the pattern of above-normal temperatures with below-normal precipitation is concerning.
Forage production from pasture and native range can vary significantly from year to year based on precipitation, temperatures, available nutrients and plant health. The first limiting factor for grass production in the Sandhills and Nebraska Panhandle is spring and early-summer precipitation. Planning to adjust stocking rates by critical "trigger" dates can help producers manage for expected shortfalls in forage production when precipitation and available soil moisture are below the long-term average.
From a rangeland and pasture production standpoint, it is good to remind ourselves of how critical available soil moisture is to plant growth. Cool- and warm-season grass species have "rapid-growth windows" when optimum air temperature, day length and soil moisture all need to be present to allow plants to fully express their growth potential. Once the "window" of opportunity has passed for a particular grass species, even if it does rain, it is too late to get significant growth from those plants.
From a grassland management standpoint, lack of soil moisture and precipitation means limited forage growth and less grass available for grazing, therefore reducing what the expected appropriate stocking rate should be for the grazing season.
Precipitation during May, June and July are strongly correlated with forage production on range sites in the Nebraska Sandhills dominated by warm-season grasses.
In the Nebraska Panhandle where many range sites are dominated by cool-season grass plants, precipitation in April, May and June is the major influencer of forage production.
Keep trigger dates in mind
Trigger dates by which to reduce stocking rates will vary depending upon the grass species present and available grazing resources. Here are some key trigger dates to consider for the Nebraska Sandhills, as well as western Nebraska cool- and warm-season dominated range sites.
• Available soil moisture on April 1. Look at dormant-season precipitation from October through March and dig 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 trigger the need to plan for a 10% to 20% reduction in stocking rates on cool-season-dominated rangeland.
• Moisture available from the middle of April to early May. Track actual precipitation and watch forecast for the next 30 to 45 days in terms of precipitation. If prospects are for below-average precipitation, additional reductions in stocking rates on pastures should be planned for.
• Late May into early June precipitation. Needlegrasses will be completing their forage production by this time and western wheatgrass is in its rapid growth window. If March-to-May precipitation was only 50% to 75% of the long-term average, a stocking rate reduction of 30% to 40% or greater should be planned for, depending upon the grass species present and plant health. Warm-season grasses such as prairie sandreed and little bluestem are just getting started.
• Precipitation and soil moisture available from mid to late June. About 75% to 90% of grass growth on cool-season-dominated range sites will occur by mid to late June. On warm-season-dominated range sites, 50% of grass growth will have occurred. Rainfall after late June will result in a limited benefit to cool-season grasses in terms of forage production, but would still result in some benefit to warm-season grasses.
• Precipitation and available soil moisture from the middle of June to the middle of July is important for warm-season grass growth.
• Precipitation after July 15 will have a limited benefit to forage production from warm-season tallgrass species, but can still result in some forage growth from shortgrass warm-season species, such as buffalograss and blue grama. However, buffalograss and blue grama produce limited amounts of forage for grazing.
A proactive approach to reducing stocking rates can help producers manage for variation in forage production. A written grazing and drought management plan that uses trigger dates for executing decisions can be helpful to producers.
Berger is a beef systems Extension educator in the Nebraska Panhandle. This report comes from UNL BeefWatch.