Accurate fertility management can reduce crop inputs this springWritten by Christy Hemken
“It seems like, as inputs get more expensive and prices are uncertain, people think more about inputs. In some crops, fertilizer hasn’t been a big issue before. Farmers just put on enough you know they’d be safe,” said Norton. “Now prices are a lot higher and it’s worth thinking about, and to me that’s a good thing because it’s better for the soil to balance fertilizer inputs with the soil and the potential yield of the crop.”
Norton outlined ways to build soil nutrients through other ways than just applying fertilizer, but he said soil testing is the keystone of doing anything different with fertility on crops.
“Wyoming has these irrigated basins that are really where the most important and high value cropland agriculture is concentrated, and that’s where it’s important to think about what’s unique about these soils and what are the ways to manage them correctly to optimize inputs and production,” explained Norton.
“On irrigated crops, water management is a huge factor in fertility management,” he said. “The high costs of fertilizers and fuels and labor are causing producers to take a closer look at their practices to reduce costs and increase profit.”
“As I look at common practices, and standard operating procedures on Wyoming’s croplands, in most cases there’s some part of an operation where they could use a lot less fertilizer without reducing productivity and especially without hurting profit,” said Norton. “But that requires better knowledge of nutrient cycle processes and crop needs and that all starts with annual soil testing, which can really pay for itself.”
He said the key is to understand different crops and what they need for nutrition in Wyoming soils. “Farmers need to understand residual soil nutrients – what’s left in the soil the following year. Fertilizer placement can also make some big differences in the efficiency and the use of that fertilizer by crops, and soil organic matter has a huge impact. It’s one of the basic soil properties that’s impacted by management, and in a big way.”
“A typical soil has a big pool of nutrients in it,” said Norton. “but the actual part of that available to plants is relatively small. These plant-available nutrients are the end products of the decomposition of organic matter.”
Depending on conditions, as this small part of this big pool becomes available, it also gets taken up back into the bigger pool by roots, plant residues and especially by soil microbes, said Norton. “They’re very competitive for these. It’s a small and transient pool, and that’s the one you often need to boost with fertilizers, especially because we’re farming desert soils in Wyoming.”
He said even though the soils are irrigated them out, the pool isn’t as big as other parts of the country, particularly for nitrogen and the other nutrients in organic matter. “Our native organic matter contents are really low and the minerals tie up phosphorous and potassium, which tend to be high in our soils but very little is actually available.”
Soil test-based fertilizer recommendations are based on the yield goal for a particular crop in a particular field. “A good way to calculate that is to take the last five years and aim for 105 percent of that,” stated Norton. “You don’t want to take the highest yield of all time as your yield goal every year because you’ll buy a lot of fertilizer that’s not utilized by the crop.”
Norton said placement method has a big impact on what will be left in the soil for nutrients the next year, as well as what the previous crop was. “If it was a legume, it might have left more nitrogen than you need, and it also depends on how the crop did. If it got hailed out all your fertilizer might still be in the soil. And if your yield was very low the crop didn’t use all the nutrients because you were fertilizing for a particular yield.”