Get soils ready to play in tune
Like a score to a piece of music, the soil test is a guide to which “notes” are being played underground, which are too loud and which are silent.
Being able to read the soil test correctly can put the baton in your hand and allow you to play a sweet tune with high-yielding crops.
Brian Hefty, a South Dakota farmer who hosts “Ag PhD” with his brother Darren on RFD-TV and radio, said knowing the basics about the soil test can help you do a better job for plants.
“Over a 30-year period, the average farmer will spend a quarter of a million dollars on fertilizer,” Hefty told a group of farmers at the Tennessee Grain and Soybean Conference recently. “Since you’re paying so much for fertility, you should probably know about fertility.”
First off, Hefty said, “your soil is a great big magnet that has a negative electrical charge.” Elements such as nitrogen and sulfur, which have negative charges, will naturally leach if conditions aren’t balanced within the soil. Phosphorous leaches the least of the major nutrients.
• Brian Hefty preaches about the only thing you can control — your soil.
• Knowing what’s in your soil can lead to higher yields.
• Keep the nutrients in adequate supply and keep them balanced.
With a soil test, the starting place is pH level. The ideal pH for most crops is within 0.5 of 6.8. A high pH, above 7.3, could indicate drainage problems, which can be corrected with tile or a surface ditch, or in severe cases, by planting high-residue crops over a period of years. A low pH, below 6.3, indicates lime is needed. While at the Dead Sea on a recent trip to Israel, Hefty realized the source of some of the yield problems in his fields: Water was flowing in, but wasn’t flowing out. “I realized I had little ‘dead seas’ on my farm that were caused by bad drainage.”
Hefty also pointed out the important balancing act between negatively and positively charged elements. The Cation Exchange Capacity column on the soil test will tell you how much of a nutrient is available for plants. “You can change the CEC with organic matter, another important reason to build up organic matter in your soil,” Hefty said. “For every 1% increase in organic matter in the soil, the average soil can hold 4% more water. Organic matter can hold negatively charged ions better than clay. I call nutrients available through organic matter ‘free nutrients.’ I look at these levels before applying N, P and K.”
With today’s high-yielding crops, farmers need to consider how much they’re taking out of the soil each year. For example, with a 200-bushel corn yield, some 180 pounds of nitrogen is used. During the season, Hefty takes plant tissue analyses “because sometimes you can have the right amount of a nutrient, but it’s not available for the crop to use. The plant tissue sample allows you to know how to fill in the dots and shows you what’s happening.”
By using plant tissue sampling, Hefty was able to increase corn yields by 60 bushels per acre on a problem field over a four-year period. He samples weekly over a couple of months during the growing season.
Hefty offered a piece of advice before buying land: Get a soil test to see what you’re going to have to do before you can get the yields you need.
This article published in the April, 2010 edition of MID-SOUTH FARMER.