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Why Wasn’t the Grass Green This Spring?

Cow by Flooded pasture
 
Cow by Flooded pasture
Photo taken by Carl Dahlen, NDSU
Discussion of 2011 late green up and recommendations for pasture turnout and dealing with flooded pastures. Kevin Sedivec, NDSU Extension Rangeland Specialist

While walking through a pasture in western North Dakota on April 25, I noticed the grass wasn’t very green. Spring was here and rain (or snow) was plentiful! What gives? 

The 2010-11 winter in the northern Plains was once again wet and cold, with twice the annual snowfall and below-normal temperatures. This pattern has become the norm lately, at least in terms of high snowfall totals. Unlike the spring of 2010, the snow remained on the ground throughout much of April, and the temperatures in April were below the long-term average. These conditions create an extended period of cold soils and a low number of heating degree days.

Range and pasture grasses grow at the same time every year, plus or minus five to 10 days. Their growth is based on day length, with yearly modifications due to heating days and moisture. The spring of 2011 has ample moisture but lacks heating days; thus plant growth will be delayed five to 10 days. 

We normally see cool-season grass growth beginning in early to mid-April in North Dakota; however, this year’s green-up will occur between mid- and late April, depending on whether you’re in the southern or northern region of state.

Impact on Range and Pasture

So, how does this late-season green-up affect range and pasture readiness?

Traditionally, tame pastures such as crested wheatgrass and smooth brome would be ready for livestock grazing in late April or early May. This year’s tame grass turnout will be early to mid-May due to the late green-up. If grazing earlier than this recommended period, cattle quickly can remove the available plant growth and reduce plant vigor, negatively affecting carrying capacity for the entire year.

Native range traditionally is ready for livestock turnout in late May in much of the state and early June in the northern regions and warm-season dominated pastures (this is when most native grasses have three to 3½ leaves). Native range turnout will be delayed this year until early June in most of the state, with the exception of pastures dominated by Kentucky bluegrass (Junegrass). These Kentucky bluegrass-dominated pastures will be ready by the last week in May. 

Interestingly, our grasses will compensate for this delayed spring growth during June. These grasses will reach the similar phenological growth stage by the end of June, when the day length peaks, thus having similar forage production potential, compared with the long-term mean, from early July through the end of the growing season. Therefore, the negative effect on grass growth this spring will be gone by late June unless overgrazed in May and June. 

Dealing With Flooded Pastures 

Numerous pastures have flooded areas this spring, leaving livestock producers wondering how the pastures will recover and when they will become grazing-ready. Spring-flooded pastureland usually recovers with no death loss (this is not true of pastures that are flooded during the growing season). Once the water recedes, the grasses will grow as the soils warm and heating days increase. 

The delayed turnout will vary on these flooded pastures, depending on the time needed for water to recede/evaporate. If flooded areas occur in larger pastures, delay grazing the normal recommended five to 10 days. If an entire pasture is flooded, delay grazing until the water has receded and the ground is sufficiently dry to minimize heavy soil disturbance. 

In summary, I recommend delaying pasture turnout this year for five to 10 days compared with your traditional turnout date. I hope your summer is productive, your livestock operation flourishes, and you get a chance to enjoy and benefit from North Dakota’s rangelands. 

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