Project aims to decrease corn irrigation requirements
Wenwei Xu, Ph.D., cannot pinpoint a gene that allows drought resistance or water efficiency in corn, but he is definitely drawing nearer to providing producers with corn exhibiting those traits.
"We will be running out of water at some point, so we need to find water-efficient or drought-tolerant corn hybrids, plus management technology to reduce the amount of water required to produce corn," Xu, a Texas AgriLife Research corn breeder from Lubbock, said during the recent Texas North Plains Corn Irrigation Research and Extension Field Day near Etter.
The AgriLife Research plots at the North Plains Research Station near Etter are among the three primary test locations established by Xu. The other two are at Halfway and Lubbock.
Xu has been conducting his breeding work since 1998 and has already released some inbred lines to commercial companies, which are using those lines in pre-commercial tests.
"We are developing new corn germplasm by using exotic materials special from tropical corn," he said.
Xu said he is not only developing new inbred lines, but also evaluating existing available technologies and in-the-pipeline products from commercial hybrids, using that information to pick up the best technology for producers.
"We select corn for a lot of traits," he said. "We cannot select corn for drought tolerance or water efficiency based on a single trait. We have to select a lot of number of traits. It's very complicated, so the water-use efficient corn is not going to be like herbicide-tolerant corns or Bt. It has to be incremental increases."
The AgriLife Research corn-breeding nursery is located in Halfway and Lubbock, Xu said. At these locations where the initial selections are made, sub-surface drip irrigation systems are used to apply water amounts that will stress the corn.
This project is funded by the High Plains Underground Water Conservation District, Texas Corn Producers Board, Texas Department of Agriculture, and the Ogallala Aquifer program funded by the U.S. Department of Agriculture-Agricultural Research Service.
"Once you stress corn you will see leaf rotting, reduced plant height, stapling traits--that's what you (the producer) are seeing," Xu said. "But for breeders, what is most important is what happens inside the husks, the ears. That takes a lot of labor; we have to hand harvest the ears and rate for seed setting and grain quality, those kinds of things."
Those traits are what his selections are based upon, he said.
"At the end of the day what you really care about is still yield, yield, yield," Xu said.
The plots at Etter are planted under a center pivot irrigation system and then watered simultaneously at four levels of crop water use or evapotranspiration, also known as ET: 100 percent; 75 percent; 65 percent and 50 percent.
While there are different types of research taking place on corn fields at the Etter location, Xu said irrigation water management is a key part of his breeding tests.
"What is the best combination to choose hybrids and plant population and irrigation scheduling?" he said. "We have 10 hybrids growing under each of those regimes with three plant populations: medium, high and low."
Thomas Marek, AgriLife Research senior research engineer and superintendent of the research field, said the target is to apply about 32 inches of water, which is equal 100 percent ET, a combination of rainfall, irrigation and stored soil moisture.
The requirement of 32 inches is down from 36 inches in the past due to improved genetics, Marek said.
The plant populations used in the breeding trials are: 33,000 plants per acre for high, 28,000 plants per acre for medium and 23,000 plants per acre for low.
In 2008, under 100 percent ET, the average yield was 266 bushels per acre for the high population, 255 bushels for the medium and 234 bushels for the low, Xu said. Under 75 percent ET, the yields were 268 bushels per acre, 263 bushels and 255 bushels in the medium and low, respectively.
"What that tells you is that we may be over-watering in this location if we use current ET network models estimation and water the field at 100 percent ET level," he said.
Marek said the evapotranspiration network corn model is based on older genetics and is used across the entire Texas Panhandle region, so things may not be specific for any one variety, area or newer genetics.
In explaining the breeding program, Xu said a farmer grows F1 hybrid seed. To get F1 hybrid seed requires two steps in the breeding program: developing parental inbred lines and then crossing the inbred lines and make a hybrid.
"It takes eight generations to develop an inbred line," Xu said. "If you have two seasons per year, it will take four years to develop an inbred line."
But even if an inbred line looks promising, it doesn't mean success, he said.
"You can develop a nice-looking inbred line, but it does not mean it will make good babies," Xu said. "So the second one is to cross the inbred lines and find the good babies. That's the F1 hybrid. And that takes another three or four years, so it takes about seven to eight years to develop a good hybrid."
Xu said he has developed a number of experimental hybrids from his breeding program, estimating that every year a minimum of about 500 hybrids are generated, but only about 1 percent are good ones.
Marek said the difference between the 75 percent and 65 percent of ET seems to be the break-over point in terms of yield reduction for many of the hybrids. Some of the work that has been done here has been cutting-edge type research in both corn breeding and irrigation management and the increased yields support that fact.
"The ear length sitting on that stalk is a little shorter, and certainly the circumference and diameter is, and the kernel fill is not as good," Marek said.
"The days are coming when you will pick a targeted water level and a genetic variety to match that production level," he said. "And the combinations that will be available are going to become increasingly confusing to producers."