Pacific Nut Producer Magazine

Tag: Crop Science Society of America

  • How is Drought Affecting Irrigation Water for Pecans?

    The holidays are a time to bake pecan pies and make salted pecans. And for the more daring, making pralines. And it seems the pecan pie has been around for about a hundred years now, originating in Texas!

    The pecan industry is substantial, according to USDA statistics. On average, pecan orchards produced around 250 million pounds of nuts per year in the past decade. The industry is valued at about $400 million USD. (We won’t calculate the number of calories in these values!)

    Pecan pie is considered a specialty of Southern U.S. origin. Credit: Canva Pro

    New Mexico was the leading state for growing pecans in 2018, beating out Georgia. This could be due to lingering effects of Hurricane Michael on Georgia’s orchards, which broke many limbs and branches. In addition, Georgia suffered from hot, dry weather in the peak nut-ripening months of August through September 2018.

    No matter who started this delicious tradition, pecans continue to be a holiday favorite. But they are grown in the south, which has been experiencing increasing drought. This is especially true in New Mexico, where some researchers studied the effects of using brackish water to irrigate this tasty nut.

    A pecan orchard. The trees grow tall, and typically are watered for 14 to 21 days during the growing season. Flowers typically bloom in spring. Credit: Jerry A. Payne

    Water in the southwest is already in jeopardy. Winter snow and rains are not replenishing water sources. Summer heat increases its evaporation. When water comes in contact with rocks or other sources of salt, some salts dissolve in the water – a natural process. But as the water evaporates, that increases the salinity of the water, because salt does not evaporate along with the water. This salty water is called brackish, which has less salt than ocean water.

    An ancient civilization called the Hohokam found out the effects of using brackish water a long time ago. In good years, when rains could wash out some of the salt in the soils, crops did well. But over time, the soils became unproductive, and the Hohokam had to move on.

    Pecans are grown in the south, where conditions are warm for the fruits to grow. Shown: pecan nuts in shell on a tree. Credit: Brad Haire

    Some crops can tolerate higher amounts of salt than others. So, the New Mexico State University team tested pecans in the greenhouse by irrigating with various levels of salt in their irrigation water. They tested both the levels of salt in the irrigation water as well as the type of soil the pecans were grown in.

    Their results indicate that continuous irrigation with salty water can be done for up to one year. However, after that, the plants showed signs of stress: “burned” leaf edges, yellowing of leaves, and branch dieback. They also observed salt accumulation due to the water evaporation at the soil surface in their test plants.

    Current conditions in New Mexico mean that scientists and engineers need to step in and work to find ways to reduce the amount of salt in irrigation water. To be able to continue pecan production under drought conditions, the water will need to be desalinated. There are several methods to do this, but they are expensive. An alternative is to breed pecans that are more drought, and salt, tolerant.

    Pecans in their brown shell with pecan nuts woven throughout. Shelled pecans are eaten alone, or used as an ingredient in pies, pralines, and more. The 2020 value of the pecan market in the United States was about $400 million, with New Mexico being the leading state of production. Credit: Scott Bauer

    This article was written by Susan V. Fisk from research published in the Soil Science Society of America Journal: “Brackish groundwater and RO concentrate influence soil physical and thermal properties and pecan evapotranspiration,” doi:10.1002/saj2.20281.

  • Research Gives Possible Answers to Increase Pollinator Populations on Farms

    Many living creatures live in soil. Though their sizes range from microscopic soil microbes to larger animals like gopher turtles, they all call soil their “home.” Included in these ground-dwelling species are bees – vital in the pollination cycle of about 90% of plant life.

    Rebecca Lybrand and her team at Oregon State University are studying the interaction between the bees and soil in agricultural settings.

    According to the recently-published paper, bees contribute $15 billion to crop value annually. They pollinate about three-quarters of the fruits, vegetables, and nuts within the United States alone. Declines in honeybee colonies are a critical threat to agriculture and the global food supply.

    “Growers who are interested in attracting alternative pollinators, such as wild bees, face a major challenge,” says Lybrand. “There are not many studies about what habitats are best for these wild bees.”

    Pollinators are widely affected by human land use. Creating buildings, parking lots and other “anthropogenic changes” disrupt the natural habitats of animals and plants. Agricultural disturbance also affects bee communities. Interestingly, above-ground bee species are nine times more affected by agricultural intensification than ground-dwelling species.

    In some cases, growers have been able to build “bee beds” in their farm setting. In the 1950s, they started to design moist, salty soil areas to attract ground-nesting bees that helped increase alfalfa yields in Washington state.

    Lybrand’s study looked at physical and chemical properties of soils collected from active bee and sand nest wasp sites in the Willamette Valley of western Oregon. They compared soil properties among seven farm sites to identify similarities and differences.

    The Willamette Valley has wet winters with warm, hot summers. The team first found agricultural sites that contained ground-nesting bees. They collaborated with farmers who observed ground-nesting bee activity around their fields.

    The nests are only identified by rather small holes (only 3-5mm). The team only collected data if they observed bees entering the nest. Nests and holes can remain even after the bees leave. At the study site, they specified the type of bee to the family level (i.e. “bee” versus “genus” and “species”.) But they also collected some bees to bring back to the lab for further identification.

    The data the team collected in the field included soil temperature, pH, and soil texture. They also collected soil samples to bring back to the lab for analysis.

    Findings from the study included that active nesting sites were present in locations with little to no rock cover and low vegetation. Nesting sites were found in areas with low organic matter coverage. The slope of the land didn’t seem to have any influence, nor did a north/south-facing aspect.

    “One of our observations confirmed that active emergence holes remained open throughout the year,” says Lybrand. “They didn’t swell shut during the wetter, cooler seasons – despite having clay in the soils that might cause shrinking and swelling.”

    An interesting finding from the research is that the team found lipids in the soil nest linings. The lipids may provide a type of waterproofing for the nests and their inhabitants.

    “Because the large majority of wild bee species nest in the soil, studies about how to best attract them to farms are important,” says Lybrand. “Soil scientists and entomologists can partner with growers to identify soil habitats that support and attract more of these pollinators to agricultural lands. Improving our understanding of the connections between agriculture and the soils that bees, crops, and living organisms rely on to survive is important. Our research also provided a framework for studying ground-nesting organisms – an area of soil science that is underrepresented.”

    Looking to the future, Lybrand says, “future research should also integrate methods that identify bees and/or wasps to the species level. That would allow for interpretations of the results from an ecological point of view. Another question to follow up on could be the nature and purpose of the lipids found in the soil nest linings, to confirm their actual role.”

    This research was published in Soil Science Society of America Journal. Funding for this project came from an Agricultural Research Foundation grant via Oregon State University.

    American Society of Agronomy, Soil Science Society of America, Crop Science Society of America: Collectively, these Societies represent more than 12,000 individual members around the world. The scientists’ memberships build collaborating partnerships in the agronomy, crops, and soils science fields for the advancement of knowledge.