Summer 2006

Northcentral

The start of the season has been mixed. Parts of the Northcentral region are showing generally good crop growth, while other areas are off to a slow start and have had to be replanted. New nitrogen (N) recommendations from universities are also being thrown into the mix of management considerations, plus fertilizer prices are higher. All of these factors add up to an increased need to focus on nutrients. In particular, it will likely be worthwhile to walk through fields on occasion and look for signs of nutrient deficiencies. An occasional plant sample can also be helpful for either confirming deficiencies associated with symptoms or finding areas that are deficient but not showing visible symptoms. For corn, end of season stalk nitrate tests taken in a few fields can help evaluate if there was enough N applied during the season. While scouting and tissue tests are not commonly done for many row crops, changes in the nutrient management situation make such additional measurements more important than ever.

Good conditions prevailed at seeding time across much of the Northeast this spring. Corn and soybeans have emerged well, and cereals are growing rapidly. In Ohio and Michigan, according to the National Agricultural Statistics Service, about 95-100% of the corn and 79-88% of the soybeans had emerged as of June 11. Around 60% were rated in good condition or better. Environment Canada predicts a hot and dry summer for every part of Canada.

Many factors affect availability of nitrogen from the soil, from manures, and from previous crop residues. Mineralization rates, leaching and denitrification losses, and volatile losses of ammonia are all controlled by the weather. A soil nitrate test this month will be very helpful—but make sure the corn is at least six inches tall before taking it.

Weed growth is often influenced by how fertilizers are applied to crops, and can respond to these crop nutrients. Often it is fertilizer placement which is the factor influencing weed response. Fertilizer placed as narrow in-soil bands, rather than surface broadcast, has been found to reduce the competitive ability of downy brome, foxtail barley, and wild oat.

It has often been reported that weeds thrive on soils with low fertility. However, recent research in western Canada has shown that this is likely not the case. In fact many of the common agricultural weeds found in the region benefit from our efforts to improve soil fertility. The biomass of many weed species increased considerably more than spring wheat or canola to added fertilizer nitrogen (N) or phosphorus (P).

It was also found that weed species varied tremendously in their response to added nutrients. Some species exhibited a strong growth response to either N or P, but not both. While other weeds responded strongly to both nutrients. Surprisingly, the biomass of many weeds increased more with added P than with added N.

Fertilizer is a major cost to crop production, making efficient utilization critical. Weeds, like annual crops, respond positively to increased soil fertility. In a worst-case scenario, crop yields may actually decrease as fertilizer rates increase. Placement of fertilizer appears to have a major impact on how these nutrients impact weed growth, and affects crop-weed competition.

Although some areas have recently received significant rainfall, the majority of the Great Plains region is suffering from some drought. The latest Palmer Drought Index shows that none of the region is above normal, and most is in some degree of drought. This has taken a toll on this year’s wheat crop. Harvest is underway and the outlook is generally pretty dismal. The bright side of this is that for growers with a wheat crop, prices are higher than normal. Remember too that where the wheat crop failed or suffered significantly there will likely be some measure of residual N in the soil. It is therefore a good idea to perform a soil N test prior to planting the following crop to see if fertilizer rate needs to be adjusted accordingly.

There has been lots of talk over the past few years about fertilizer price and its impact of optimum rates of application. PPI has generated many publications on this issue in response to these concerns. Fertilizer and crop prices do have an impact on optimum rates of nutrient application, but the impact is not as great as one might at first think. Economists at Kansas State University recently published work (article and spread sheet) addressing the modification of yi eld-goal based fertilizer recommendations to reflect price (Kastens et al., 2005. >article<, >spreadsheet<). Mathematical functions were developed using historical N trial data from western and north central Kansas involving wheat, corn, and grain sorghum. Their work is detailed and extensive… its entirety beyond the scope of this brief update, thus links are provided in the above reference for further exploration. Using this tool, for wheat (60 bu/A yield goal) at $0.45/lb N, the recommended N rate ranged from 67 to 77 lb/A from $3.00 to $4.50/bu, and at $4.00/bu wheat, the rate ranged from 74 to 85 lb/A from $0.45 to 0.25/lb N. For corn (180 bu/A yield goal) at $0.45/lb N, the recommended rate ranged from 171 to 188 lb/A from $2.00 to $2.75/bu, and at $2.50/bu corn, the rate ranged from 183 to 205 lb/A from $0.45 to 0.25/lb N. The optimal N rates determined by this tool vary relatively little with changes in N and crop price. However, one of the things the tool illustrates is the fact that as crop price increases the impact of fertilizer price diminishes. This is an important fact to consider, especially for those with intentions of planting wheat this fall.

Although there has been some slight relief in fertilizer costs since winter, the changes did not come in time to affect many farming operations in the Southeast region. A number of farmers and crop advisers closely examined their budgets and finances, and many elected to pare back on fertilizer inputs. Unfortunately, a few calls have already been received to inquire about the effectiveness of side-dressed potash for corn in fields with very low soil potassium values. Such questions are avoidable when one soil samples correctly, and follows the basic soil test nutrient recommendations. We are anticipating that this could prove to be an educational season for many who elected to flirt with potential nutrient deficiencies by cutting back on fertilization.

Weather from Florida and Georgia to Arkansas has been unusually dry, which tended to slow planting of corn, rice, cotton, and soybeans, and it has tended to slightly delay flowering. After some rain fell, the pace of planting was rapid. In some areas, a cool, wet spell that followed caused decreased emergence and thin, weak stands. So, more acres were replanted than would have been desired in a year when input expenses are being watched so closely. Nevertheless, crop conditions are reported as mostly fair to good across the region. Cotton is squaring in most states, while more southern plantings are reporting the start of flowering.

Wheat harvest has begun in the Midsouth with reports of fairly good yields; 50 to 70 bu/A. Soft red winter wheat acreage harvested in the PPI Southeast region this year is expected to be about 20% greater than was harvested last year, and yields are expected to be slightly higher also.

The peach crop in Georgia and South Carolina is expected to be down from the 2005 crop harvest.

Rice acreage was hurt in southwest Louisiana because of the after effects of excess salinity associated with hurricanes last year and salt water intrusion. Pasture and hay conditions have degraded due to lack of adequate rainfall.

The acreages of spring planted crops will likely not be known until near the end of June.

Hurricane season has begun again and forecasts are not overly encouraging. NOAA predicts an 80% chance of an above-normal; hurricane season. Their outlook calls for a very active 2006 season, with 13-16 named storms, 8-10 hurricanes, and 4-6 major hurricanes. The likely range of the ACE (accumulated cyclone energy) index is 135%-205% of the median. This indicates a continuation of above-normal activity that began in 1995. The good news is that they do not currently expect a repeat of last year’s record season.

According to the USDA, “Rust has been confirmed in five counties in Alabama, 11 in Florida, four in Georgia, and one in Texas. Many of the Southern states are experiencing hotter and drier than normal conditions, reducing the likelihood of viable spore dispersal.”

The USDA normalized difference vegetation index (NDVI) maps are shown below for the end of May 2006: both spot and departure from the 4-year average.

Crop Deficiency Symptoms – Keep a Close Watch This Year!

Some growers cut their fertilizer application rates this year to levels that may not sustain healthy plant growth through the entire season. Insufficient nutrition will lead to increased plant stress, enhanced susceptibility to disease, slower growth, delayed maturity, and lower yields.

Are you able to identify nutrient deficiencies from plant symptoms in the field? If not, it is time to go out and gather some information that will help interpret some of the symptoms you observe. For some helpful pictures of these symptoms, go to the PPI website (www.ppi-ppic.org) and enter the crop in the “images” section.

Plant tissue samples collected during the growing season can be used to diagnose the hidden yield-robbing nutrient problems that may not have observable symptoms. While this diagnosis may not be in time to take corrective action, it provides information for future nutrient decisions. Also, remember that by the time deficiency symptoms are visible in the field, significant losses in production have already occurred.

When nutrients have been built to adequate levels in the soil during past years, it may be possible to temporarily cut application rates to take advantage of these stored nutrients. Any reduction in application rates should only be done with guidance from soil test results in order to avoid production problems.