Winter Planning for High Production in Irrigated Pastures
In irrigated pasture management there are many places to spend money, but four common areas make the greatest economic impact on pasture and grazing income. The economic impact areas include: pasture fertility, pasture fencing, pasture seeding and irrigation improvements. This article will concentrate on pasture fertility.
In a recent test, cool season irrigated pasture maximum production under “ideal conditions” was measured. Water and fertility were closely managed. The pasture test plot was clipped and weighed repeatedly during the growing season. The test showed under “ideal conditions” irrigated pasture production can approach 20 tons of dry forage per acre. It is exciting to think of the possibility of pasture producing 20 tons of forage. However, the economics of doing this on a large scale would not be practical or profitable as the plot was extremely moist at all times and maximum production used a great deal of fertilizer.
The largest management variables in achieving high cost-effective levels of irrigated forage production are fertility and fertility timing. A pasture populated with modern forage varieties can use 300 pounds of available nitrogen during the annual growing season. The economic feasibility of applying 300 pounds of available nitrogen is not cost effective. Fertilizer could cost more than the forage gain. There is a logarithmic increase in forage production with available nitrogen until roughly 150 pounds of nitrogen per acre. After 150 pounds of available nitrogen a gradual leveling off of production is observed. It is recommended to divide fertilizer into three applications, early, mid-season and approximately August 1st. It is not recommended to apply 150 pounds of available nitrogen in one large application.
Studies show timing of fertilizer application is important in irrigated pasture production. An application of approximately 70 pounds of available nitrogen when annual centigrade degree days reach 200 show an increase annual pasture production by 30% when compared to applications later in the growing period. Degree days are regionally variable and should be calculated using public access weather stations near the pasture site. For example 200 degree days is in mid-January in the Walla Walla region while it takes until the first part of February in the Yakima region.
Best management practice includes the use of soil samples annually, prior to developing a fertility management plan. Having 70 pounds of available nitrogen available at 200 degree days is important. A second application of 50 pounds of nitrogen should be applied to irrigated pasture around the time when the region is cutting hay for the first time. June 1st in the Yakima region, is advised. The third application of 50 pounds of nitrogen should be timed around August 1st to capture the second growth curve of cool season forage species and aide in meristem production for the next season. Sulfur and phosphorus can be important fertility additions. Consult professionals in your area to plan fertility management.
Answering the key question, is it economically feasible to fertilize irrigated pastures with 150 pounds of available nitrogen, the answer is yes. Several years ago, when nitrogen fertilizers were higher than $1,000.00 per ton, the numbers showed fertilizing at this level was profitable. At today’s nitrogen prices (approximately $550.00 per ton) it is feasible, profitable and intelligent to spend money on soil testing and fertilizer in irrigated pastures. Every dollar spent on fertilizing results in $19 to $35 of forage production, depending on forage plant species, population and several other variables. A fertility plan should be one of the highest priorities in a managed intensive grazing program.
Previously published: WA Cattlemen's Association Ketch Pen-January, 2011
Authored by: Frank Hendrix, WSU Extension Educator-Livestock, Pasture Mgmt
Read more on pasture improvement & Frank's work:
~ Intensive Grazing Trials
~ Is Improved Pasture Economically Viable
~ Easier Irrigation
