Charles Schlabs feels fortunate that his fertilizer program virtually guarantees no injury to cotton. He relies on manure from local feedyards to provide nitrogen (N) and other nutrients. But he also knows that too much of a good thing can take the fluff out of a good crop.
Fertilizer injury caused by at-planting in-furrow N applications, or even aphid infestations pushed along by excessive N treatments in-season, can decrease cotton returns, either in yields or through higher production costs.
“We haven't had any fertilizer injury problems in a long time,” says Schlabs, a Hereford, TX, grower who rotates cotton with corn under irrigation. “With our feedyard manure applications, we might see slight damage resulting from too much application when the truck starts off. But that can be corrected during disking.”
Sandy Stewart, Louisiana State University cotton agronomist at Alexandria, says most growers do a good job of preventing crop damage with precise fertilizer applications.
“There are two cases in which fertilizer damage can be a problem,” he says. “One is with in-furrow liquid starter applications. Another is with foliar applications of urea.” A grower is “playing with fire” when he goes with the in-furrow liquid starter because of potential seed damage, says Stewart. He suggested using a “two-by-two” sidedress, or applying liquid fertilizer 2 in. to the side of the row and 2 in. deep.
A foliar application of most fertilizer usually won't harm cotton, unless urea is used in a low-volume carrier. “That can result in leaf burn,” says Stewart.
Research funded by Cotton Incorporated suggests that one bale of cotton requires 50-55 lbs. N/acre per year. So a 2- or 3-bale crop would require about 100-110 lbs. and 150-165 lbs. N/acre. Schlabs obtains that ratio from manure.
Fortunately, he farms within a half-hour of feedyards that finish several million cattle a year. Dry manure from those yards is an economical, organic source of N and other nutrients. He receives the N his cotton needs from a single manure application that lasts up to five years.
“We apply manure at about 20 tons/acre once every four or five years,” he says. “That provides most of the N needed for our corn and cotton rotation. We also get residual N from corn that precedes cotton.”
Dry manure is broadcast by special truck attachments. The material is usually free from feedyards. “We've even been paid by some yards to take it,” says Schlabs.
“Application cost is about $2.25/ton, plus 15¢/mile for hauling from the feedyard. Overall we pay about $3.50/acre for the application (which is incorporated by disking). That's $70/acre, but that breaks down for four or five years. So it is pretty cheap,” he says.
Any volunteer weeds from the manure are controlled with glyphosate herbicide on the Roundup Ready cotton, or with a residual herbicide after the first year.
This program frees him from much chance of fertilizer injury. And there is rarely too much N, which can cause other problems.
Over-fertilization with N is a contributing factor in mid-season aphid problems in Texas, Cotton Incorporated research says. And over-fertilization can delay maturity.
“Growers need to monitor their N applications, both because of the high cost of fertilizer and the potential for damage with mismanaged use,” says Stewart.
Forget too much of a good thing.