The delicate nitrogen balance behind Californian almond production

Balancing nitrogen levels when farming almonds is a tricky business.

A favourite healthy snack, almonds are a staple on grocery store shelves worldwide, with more than 80 percent grown in California. As permanent crops, almond trees have unique needs and challenges for farmers.

Sat Darshan Khalsa, a member of the Soil Science Society of America (SSSA) studies how almond trees use the key nutrient nitrogen and how farmers can ensure that crops receive enough of what is a potential pollutant. He recently presented his research at a virtual meeting of the American Society of Agronomy (ASA) and the SSSA.  

Almond farming

Farming almonds can be quite different to cultivating regular crops, as Khalsa explained: “These crops are an intersection between agricultural and forest ecosystems. Similar to annual cropping systems, deciduous permanent crops like almonds are intensively farmed. They receive high inputs of fertiliser and water with high nutrient outputs.”

At the same time, crops like almonds are managed under no-till conditions – an agricultural technique whereby soil is minimally disturbed. According to the ASA, tilling or digging of any kind would disturb the trees’ roots. In addition, almond trees shed leaves, grow woody tissue and undergo other processes similar to trees in a real forest. These all have an effect on carbon, nitrogen and other nutrient cycles.

These characteristics can often mean that nutrients flow off of the field. They can get into areas like groundwater aquifers, where they can impact drinking water supplies for rural communities. Khalsa’s work has tried to minimise this issue.

“Nitrogen is the primary nutrient tied to productivity,” he said. “At the same time, it’s an important pollutant that impacts air and water quality. Through our work, we can show that many almond growers in California are in a good position to continue to be highly productive. At the same time, they can protect, or even improve, environmental quality.”

Khalsa and his colleagues specifically studied a concept called nitrogen use efficiency. It helps farmers balance putting enough nitrogen on a field while still protecting environmental quality. The research team believe their study demonstrates that it is indeed possible to use high levels of nitrogen efficiently and sustainably.

One of the conservation techniques is nutrient budgeting. This is where inputs and outputs from a field are precisely measured to try to make them as balanced as possible. Nutrients within leaves and soil are also monitored.

Almonds are eaten as a healthy snack around the world, but 80 percent of the nuts are grown in California.

Another technique outlined by the ASA is fertigation, where fertiliser is applied through the irrigation system in a very targeted way, allowing it to be precisely measured and timed to meet the plants’ needs. The ASA believes the work of Khalsa’s team can also be applied to other specialty crops around the world to help farmers have a higher income while producing nutritious food.

“Matching supply and demand is the foundation of the 4R framework with the goal of improving the efficiency of nutrient management,” Khalsa said. “The 4R framework is: the right fertiliser source at the right rate, at the right time, in the right place. That’s what will help us be more efficient.”

Challenges remain in understanding how crops like almonds cycle nitrogen year-to-year and how farmers apply nitrogen fertiliser. Khalsa also said that the research emphasised the importance of utilising information networks, including Certified Crop Advisers and Cooperative Extension.

According to the ASA, efforts to address these agricultural issues must focus on the desires and needs of the farmers, growers and industry organisations. It believes that this kind of focused, collaborative work helps promote adoption and creates new research opportunities, such as assessing soil health practices in orchards.

Khalsa also encourages researchers to maintain curiosity throughout each step of the food value chain. He believes this allows them to better understand how their research interests align with other scientists, policy makers and individuals like consumers within food and farming industries.

“After decades of working with plants, soil and water, I personally think that through understanding people, we will be able to solve the biggest problems. Agriculture plays an essential role in communities worldwide. I find no better way to connect with anyone, anywhere than through the food we share,” he concluded.