Nov. 17, 2011 - Mark McFarland, a soil fertility specialist with Texas AgriLife Extension Service, has spent much of his career studying the most efficient uses of nitrogen and phosphorous in fields and pastures. He has touted, for a long time, the importance of a soil test to determine what nutrients are already available in the soil. After fertilizer prices spiked in 2003, the realization that a lot of producers were putting out a lot more fertilizer than they needed became a bottom-line issue.
McFarland still reminds producers whenever he can that the nitrogen, phosphorus and potassium already in the fields is money in the bank. Global demand, especially from China and South America, along with increased transportation and energy costs, have fertilizer prices close to the historic highs of 2008. The market bends depending on how much the highest bidder is willing to pay. The disastrous year the state's farmers and ranchers have experienced makes efficient use of fertilizer even more important.
"Now is the time to get really serious about soil testing," McFarland told a crops and livestock clinic in Taylor earlier this month. "I know the number of producers who actually soil test is low, but there is an opportunity here. There's money in the soil bank that we want to take advantage of.
"A soil test will tell you how much (fertilizer) is still out there and how much you won't have to replace. A lot of us put out fertilizer this year thinking we would grow something. What we put out is likely still there. It might be worth more now than it was when we put it out because the price has changed."
Another game changer has been the drought. While it damaged or destroyed yields all over the state, the one bright spot is that nutrients applied last year should carry over during the drought. McFarland's research has tested soils much deeper than most producers want or need to test but he found that nutrients like nitrogen, sulphur and boron are mobile and can move a lot deeper than the six inches covered by most soil tests.
"We sampled down to four feet all over the state and found nitrogen in the soil at the end of the cropping seasons," he said. "It ranged anywhere from 80 pounds to 300 pounds. In one case there was 800 pounds left. If we put out fertilizer based on a yearly goal and the yield is lower than that, the rest of the fertilizer is still there. If we put out 100 pounds of nitrogen this year and didn't grow diddly there might be a lot left in the soil."
In research trials, McFarland and other researchers had the same yields using no nitrogen as adjacent fields that did apply nitrogen. Some of the cotton that had a nitrogen application was taller and greener but the yield was exactly the same. In Colorado County, the nitrogen-laced cotton and the cotton grown without any applied nitrogen each yielded 2.83 bales per acre. Similar research on corn and sorghum yielded similar results. The yields were about the same but McFarland calculates that it was $10-$80 cheaper to grow and harvest the fields that weren't fertilized.
"We're not telling you not to put nitrogen out," he said. "We're telling you to get a soil test and put out your fertilizer based on the results."
Similar to nitrogen, phosphorus has become expensive as well. Unlike nitrogen, it's stable and immobile; it stays put. It is most effective when it is banded six inches deep in the soil, into the active moisture zone which, despite the drought, is still there.
"Forage is a big issue on forage stands as well," McFarland said. "Get the phosphorous out now so you can incorporate it. It will be top dressing after that."
Producers in the Blacklands don't worry too much about potassium because it's usually present in the soil but the region is not immune to potassium deficiency but most of the time the real cause is water deficiency.
"As yourself, 'do I need potassium or do I need water?' One, you can do something about. The other one, you just have to pray for," he said.
