Text 3. Fertilizer Recommendations.
Onions require a good supply of available nitrogen (N), one of the primary macronutrients; however, excess N applications can result in late maturity, large necks that are difficult to cure, soft bulbs, and poor storage quality. A higher percentage of fertilizer N is absorbed by the plant if the fertilizer is applied when the onion root system is well developed. Split applications of nitrogen are used more effectively by the plant than a single pre-plant broadcast application. Fertilizer N applied before planting should be incorporated into the plow layer or banded well away (6") from the seed on the furrow side of rows in two-row onion beds. Sidedressed nitrogen applications or nitrogen applied in irrigation water can be an effective means of providing supplemental nitrogen to the crop during the season. Nitrogens such as 28% N (Urea ammonium-nitrate) is a recommended form to use for fertigation.
Excessive rainfall and irrigation that cause nitrogen movement beyond the root system can reduce the amount of nitrogen available to the plants. Additional nitrogen may be required during the season under these conditions. Cool weather during the growing season can reduce nitrogen release from organic matter. Under these conditions, the nitrogen rates should be increased particularly on organic soils. Excessive nitrogen available to onions, particularly later in the season (mid-July), can delay onion maturity and make field curing of onions more difficult. Inadequate field curing before storage can result in greater losses due to rot. Onion varieties which differ markedly in yield potential can be expected to differ somewhat in their requirements for nitrogen. Higher yielding varieties may require slightly more nitrogen. Plant populations of lower than 4 plants per foot of row will require less nitrogen.
Phosphorus (P)is essential for vigorous early growth of seedlings. All phosphorus should be applied at planting, if necessary. P can be banded at planting 2" to the side and below the seed. All potassium (K) should be applied and worked into the seed bed before planting. Onions require medium levels of available soil potassium. The K soil test onions (dry) is based on K present in the surface soil (0-12").
The secondary macronutrients, calcium, magnesium, and sulfur, are generally not limiting to crop production in most Minnesota soils except under certain conditions.
Micronutrients includemanganese (Mn), boron (B), zinc (Zn) and copper (Cu).
UNIT III
WHEAT
Text 1. Crop Development.
Progress of the 2006 wheat crop followed an unusual pattern. Planting and emergence were close to the pace of recent years, but pulled ahead in the last two weeks of October. Jointing began at the average time in late March, but soon began to pull ahead of the average pace, much like last year. Most of the wheat crop was jointed by late April, significantly earlier than the 5-year average. Heading was particularly early, after a warm spell in April. Nearly three quarters of the wheat crop had headed by the first week in May, 40% more than in previous years. The early development of the crop continued through maturation and harvest. Harvest was essentially complete by the July 4 holiday.
The condition of the 2006 wheat crop reflected constantly changing soil moisture availability and temperatures. The first reports in late October indicated that roughly 70% of the crop was rated as either good or excellent. Steadily decreasing soil moisture over the winter months was reflected in a similar decline in crop condition until late March, when only about a quarter of the crop was rated as good or excellent. Late-March precipitation led to a short-term improvement in crop condition, but hot, dry weather followed by freezing temperatures in mid to late April caused further deterioration in crop condition. Crop condition continued to decline until early June, when only 16% of the wheat acres were rated as good or excellent, and 53% were rated as poor to very poor, leaving 31% in the fair category. Crop condition rebounded somewhat with June precipitation, but the effect of these late-season rains on final yield varied greatly.
Text 2. Weather.
The 2005-06 wheat season was characterized by uneven conditions, both in temperature and precipitation. While some locations saw a wet start to the season, with precipitation more than three inches above normal, other locations saw an extremely dry start to the winter. Overall, the winter was mild and dry, with many locations having the driest December-to-February period on record. March saw a brief respite for the hardest hit regions, with a timely snowfall in southwestern Kansas. The moisture did not continue, and the western third of the state averaged less than 40% of normal April rainfall. Injury from the moisture deficit was compounded by a freeze on April 26 and 27, when low temperatures dropped as low as 26 �F, and stayed below freezing for several hours.
The uneven rainfall pattern continued through May and June. Some locations received sufficient quantities, while locations only a few miles away were much below normal. This contributed to the uneven yields within counties and across the state. Major hail storms on March 12, March 30, April 15, April 23, and May 7 also contributed to yield reductions in a few locations.
The continued warmer-than-normal conditions and generally dry weather allowed harvest to progress much more rapidly than normal. More than 90% of the harvest was completed by the 1st of July.