California farmers deal with complex irrigation and fertilization requirements of "specialty" crops within diverse rotations. Some of these so-called specialty crops have a farm value of more than $4 billion per year. These high-value crops demand careful management of both water and nutrients to achieve high yield and consistently high quality.
A recent study from DuPont Pioneer outlined the continuous-corn yield penalty, and the causes for that penalty. Over a six-year period, the study found that continuous corn yields, on average, 25 bushels per acre fewer than corn that follows soybeans.
For Dr. Paul E. Fixen of the International Plant Nutrition Institute (IPNI), the 4Rs are more than a good fertilizer practice, they are a state of mind. The senior vice president oversees efforts in the Americas, Australia and New Zealand, and is also director of IPNI's global research efforts.
Having an adequate supply of nitrogen (N) is vitally important to a crop for two reasons: First, crop plants need N to form chlorophyll in leaves, and if there is a shortage of chlorophyll, the crop will not be able to effectively harness energy from sunlight to photosynthesize and form sugars that are needed as energy sources to power plant growth, as well as form carbohydrate starches in grain or other storage organs (e.g., tubers in potato); secondly, N is a critical component of amino acids, which are the building blocks for protein formation in plants. A shortage of N results in lower-than-wanted protein contents of crop grains, or leaf and stem tissues of forage crops.
In really wet years, a lot of preplant nitrogen (N) is lost.Wet weather causes N losses somewhere virtually every year. In 2008 and 2009, very wet weather caused major N losses in a huge chunk of the Corn Belt. “My rule of thumb is that more than 16 inches of rain from April through June — or more than a foot in May and June — will lead to N deficiency problems in a substantial number of cornfields,” says University of Missouri agronomist Peter Scharf.
Applying nitrogen (N) again this year? Chances are you applied N on the same field last year — that is, you’re one of the many farmers planting more corn after corn. In the Midwest, much of the additional corn acres are coming from ground that farmers previously rotated to soybean production every other year. So now, instead of applying N once every two years, many are applying N every year.
Mother Nature pummeled farmers across the U.S. this past summer (2012). Crops wilted and collapsed, soils parched, and some streams faded to trickles. Important nitrogen (N) management questions were faced by farmers suffering through this drought.
Ammonia (NH₃) is the foundation for the nitrogen (N) fertilizer industry.
Ammonium nitrate was the first solid nitrogen (N) fertilizer produced on a large scale, but its popularity has declined in recent years.
Yield response of corn to nitrogen (N) and phosphorous (P) and soybean response to P has been documented to vary within and between fields. USDA and university scientists, Drs. D. Lambert, J. Lowenberg-DeBoer and G. Malzer, reported findings from a five-year study evaluating yield variability and the profitability of variable-rate application (VR) of N and P.¹
Risks associated with fall nitrogen (N) applications fit into four categories: logistical, agronomic, environmental and economic, the last of which currently ties very closely to the others and will be discussed in conjunction with them.
Some growers are considering a shift from a corn and soybeans rotation to continuous corn. More nitrogen (N) will be needed since soybeans will no longer provide some residual N. Other nutrient needs will also change, especially phosphorus (P). Corn, unlike soybeans, is planted early in soils that are more likely to be cool, moist and with a heavier residue cover. These conditions can suppress the uptake of P by corn and increase the likelihood of crop response to fertilizer P. Research shows that P, with some N, applied in a band two inches to the side and below the seed, boosts seedling access to a readily available supply of P.