Texas High Plains farmers likely will need little pre-plant irrigation to get 2005 crops off to a good start, according to High Plains Underground Water District No. 1 sources.

The water district and the USDA-Natural Resources Conservation Service (USDA-NRCS) conducted a limited annual pre-plant soil moisture survey this year to determine how heavy rainfall received across the district in 2004 will affect 2005 crop prospects.

“Abundant rainfall in the fall and winter added moisture to the soil. Because of this, very little pre-plant irrigation is expected at the start of the 2005 growing season,” said Gerald Crenwelge, USDA-NRCS Soil Scientist.

The survey is a one-year exercise, Crenwelge said. However, representatives from both agencies believed data should be collected at some monitoring sites to get representative soil moisture values within the water district's 15-county service area. Pre-plant soil moisture readings were taken Jan. 17 through Jan. 25, 2005, at 40 sites evenly distributed within the water district.

The average soil moisture deficit, or amount of additional moisture the soil could hold, averages 2.5 inches in the upper five feet of the soil this year. That compares with 5.4 inches of soil moisture deficit in Jan. 2004. “This indicates almost three inches more moisture in the soil than last year,” Crenwelge said.

He added that the average available moisture values, or amounts of plant-available moisture in the soil, show the same trend. Readings indicate an average of 6.2 inches of moisture in the upper five feet of soil, compared to 3.2 inches in 2004.

Five-foot soil profile not full

Despite the above-average rainfall last year, the data collection revealed that moisture did not completely fill the five-foot soil profile. Crenwelge said several factors contributed to this.

“The soil infiltration rate, or how fast water can enter the soil, becomes slower as the soil surface becomes wetter. Water will pool on the surface and then flow from fields as runoff. Since the fields were already wet at the surface, much of the moisture ran off the field before it could soak into the soil,” he said.

He added that as soils become wetter, water is “wicked” down into the lower portion of the soil profile, which may take some time — especially in heavier clay soils.

“Also, the soil was wetter at the five-foot level than it was last year. Therefore, some moisture soaked deeper than the five-foot level,” he said.

Most areas have received additional rainfall or snow since the soil moisture readings were made in January. “This additional moisture should be very beneficial for crop production,” Crenwelge said.