Stripe rust developing rapidly

This graph from the Kansas State University Cooperative Extension Web site on wheat production illustrates the impact on yield from water stress at various points of development. As Nebraska's wheat enters the heading and flowering stages, it is most vulnerable to potential yield loss from water stress (http://www.oznet.ksu.edu/pr_aawf/June-water_use.htm).

While frost damage was not readily apparent this week, if wheat pollen was affected, problems in head development should become apparent in the next week. Basal stem stress usually does not appear until near maturity and typically presents itself as unusually high levels of lodging. This symptom will likely become more visible near harvest in cold spots in some fields.

A greater concern at this point is that while wheat stands in many areas are thick and appear almost lush, the winter wheat in western Nebraska may be reaching a critical juncture - many fields have used up stored soil moisture and unless they receive rain during the next 10 days, yields will be dramatically reduced. Those areas that missed the last thunderstorm already are starting to show stress which may increase with continued warm temperatures.

In the Panhandle winter moisture was not excessive and many areas are still at or below average rainfall. A medium textured soil can only hold 1.50-2.0 inches of water per foot. Wheat will start showing stress when about 60% of this water has been depleted. Producers can calculate how much stored soil water they gained through the winter, how much precipitation they received this spring, and determine if there is any stored moisture remaining and whether irrigation may be necessary. In many areas irrigation is likely warranted to avoid plant stress.

Wheat water use

Winter wheat in Nebraska uses 18 inches of water on average per season. Conditions affecting water use by wheat include climatic conditions, variety, fertility, stand, crop residue, and others. Following are some general guidelines as to how much water wheat typically needs at various growth stages:

3.5 inches - emergence to spring growth

3.5 inches - spring growth to jointing

2.0 inches - jointing to boot

2.0 inches - boot to flower

3.0 inches - flower to milk

1.5 inches - milk to dough

2.5 inches - dough to maturity

The figure indicates that if a drought occurs, wheat would suffer the greatest yield loss during flowering.

Within the water used by wheat, it usually responds to water at 5-6 bushels per acre per inch of water but may vary from 2 to 6 bushels per acre. This figure applies after the minimum 4 or more inches of water required for plant establishment. This depends on everything else being adequate or not affecting production, including stand, fertility, disease, insects, and weeds. Most soils can store 1 to 2 inches of available soil water per foot. Wheat can, if rooted down, extract water to a 6-foot depth if moisture is available. Soil water levels in dryland wheat can be depleted by up to 75-80% of the available water level without serious potential yield reductions at most growth stages. However, for irrigation the recommendation would be to maintain soil water above 50% to maintain yield potential throughout the growth cycle.

If your wheat has 2 feet of soil moisture and your soil stores 1.5 inches of available water per foot you would have 3 inches of soil water. This can be depleted to a maximum of 80% before affecting yield so you can use 2.4 inches of available soil water before stress. If the wheat is now flowering you need 7 inches of water and have only about a little more than a third of the soil water you need to get the crop to maturity for maximum yield. Therefore, timely June rains are needed to maintain chances for optimum yield.

Late season grasshopper feeding in corn in 2002.

Rangeland areas apparently have the greater infestation. There have been a few hatches in areas adjacent to cropland, but the numbers are low. This is also the case for the Adams, Webster, and Kearney county areas where there is a mixture of grass feeding and general feeding grasshoppers in pastures and areas around cropland.

Recent rainfall has probably helped reduce the number of early hatching summer feeding grasshoppers, but there are still a large number that have not hatched yet. Some species do not begin to hatch until early June. There are also a number of species with a lengthy hatching period. Some species begin to hatch in mid-May and will continue to hatch until the end of July.

This is particularly true for the crop damaging species and for one of the most damaging pasture feeding grasshoppers. The largeheaded grasshopper is an important pasture feeding species that generally starts hatching in early June and continues to hatch until mid-July. Two of the most important crop feeding grasshoppers, the differential grasshopper and the redlegged grasshopper, are also later hatching species. They usually start to hatch in early June and continue to hatch until late July.

These extended and late hatching periods suggest the need for continued scouting for grasshoppers in pastures and areas adjacent to cropland. It is important to identify hatching beds and begin to assess the number of grasshoppers present. These observations will be used in the next few weeks as control decisions will need to be made starting in mid-June.

Recently, early instar cutworms (small) have been found feeding on these crops in some areas. These cutworms are the climbing type that 'graze' on crops, usually causing limited damage unless populations are too extreme and cause defoliation that is too extensive for very small plants. Growers are urged to watch establishing fields for these cutworms. Significant damage will only develop if small plants are threatened with heavy cutworm populations.

The extent of the spread of this aphid is not known, but if Russian wheat aphid damage is seen in resistant lines and the presence of this Russian wheat aphid is suspected, please contact Gary Hein at the Panhandle Research and Extension Center in Scottsbluff at 308-632-1369 so this development can be documented.

Table 1. Drought periods of five or more years duration at Ash Hollow, Nebraska. (C,A, Woodhouse and J. T. Overpeck, 1998. 2000 years of drought variability in the central United States. Bulletin of the American Meteorological Society, 79(12): 2693-2714.) First year Last year Duration of Years between drought (years) droughts 1220 1231 12 1260 1272 13 29 1276 1313 38 3 1383 1388 6 33 1438 1455 18 16 1493 1498 6 38 1512 1529 18 13 1539 1564 26 10 1587 1605 19 23 1626 1630 5 20 1668 1675 8 38 1688 1707 20 13 1728 1732 5 21 1761 1773 13 29 1798 1803 6 26 1822 1832 11 25 1858 1866 9 25 1884 1895 12 18 1906 1913 8 10 1931 1940 10 17 1952 1957 6 11 Average 12.8 23.9

Nationally, drought was a major event in 2002 with more than 50% of the United States experiencing drought that summer. This was the greatest area of drought across the country since the mid-1950s. According to the July 23 Drought Monitor map, drought or abnormal dryness was occurring in all 50 states. The 2002 drought event was actually a continuation of a series of drought years for the Republican River Valley in southwestern Nebraska that began in 1999. Recent droughts occurred across portions of Nebraska during early 1996, 1988, 1989, and during the mid-1970s from 1974 through 1976.

A long history of droughts

So far, these recent droughts do not compare to those endured in the 1930s and 1950s, and many believe that it is unlikely that a drought of their severity will ever occur again. But just how unlikely are the droughts of the 1930s and 1950s? Soil scientist Harry Weakly with the USDA Soil Conservation Service (now NRCS) looked at tree-ring records in western Nebraska and put together a table of multiple-year droughts of five years or longer between 1200 and 1960 (Table 1). This information has been confirmed with more recent paleoclimatic studies of the Great Plains region, like Woodhouse and Overpeck (1998). Table 1 reveals that the 1930s drought is not an unusual; in fact, the Dust Bowl years look rather tame compared to some of the previous droughts, like the 38-year drought in the late 1200s and the 26-year drought in the mid-1500s. Certainly, not every year in a multiple-year drought was dry, but the overall trend was dryness. These droughts had significant impacts environmentally, and affected the Native American and European settlement patterns.

UNL researchers have studied past precipitation records to see if they might yield clues about future rainfall trends. Steve Hu, climatologist with the UNL School of Natural Resource Sciences, has found that the precipitation patterns for Nebraska summers reveal 20-year and 40- to 50-year cycles. When both of these cycles become "negative" together, as they did during the 1930s, multiple-year droughts occur across the state. Dr. Hu points out that these two cycles once again are trending toward the "negative," and he predicts that the next several years could continue to be part of the recent dry pattern that the state has been facing.

Planning for drought

Given the likelihood of continued droughts, Nebraskans need to plan not only for short-term droughts, but also for long-term droughts. The state recently revised its drought plan, first written in 1989, to include mitigation actions that the state can take when drought is not occurring so that the impacts from future droughts will be reduced. Municipalities across the state, forced into action by the 2000 and 2002 droughts, are beginning to assess their drought vulnerability and are starting to consider the process of drought planning.

Farmers and ranchers across the state also can plan for drought. Having a plan in place can help a producer make better, more timely financial and farm management decisions, and it also will leave the producer prepared to take advantage of any state or federal assistance that might become available.

A producer's drought plan focuses on identifying critical dates and decisions that must be made. It should also highlight actions the producer can take to reduce the risk to drought. One action that producers should take is to improve their documentation of their operation. This single action, which would include improved record keeping, weather information, and taking photographs of conditions, would simplify interactions with state and federal officials, crop insurers, bankers, and others that could provide valuable assistance to the producer when needed and limit potential delays.

Recognize that the government has made a large investment in every tract of land that is enrolled in the CRP. Each site has required expert technical assistance to determine eligibility under the rules, seeding recommendations, follow-up assistance and monitoring. The largest up-front expense was the cost-share funding to establish the permanent cover. Considering the investment, it is understandable that the government would want the contract to stay in force for the full term. The law stipulates severe penalties for cases when the owner does not comply with the rules or intentionally breaks the contract.

A lot of the alfalfa first cutting is complete but getting the hay baled has been a challenge. This week did provide a window for harvest for producers who were finished planting. Some early wheat is heading, but much of it is still in the joint stage. The wheat crop is looking good but only the combine can really tell yields. Some rust has been reported.

A second fact sheet examines the groundwater chemistry and management of the Dakota aquifer, the state's most important secondary aquifer.

In "Water Transfer and Marketing in Nebraska," Michael Jess, acting director of UNL's Water Center and associate director of the Conservation and Survey Division, addresses Nebraska laws that regulate transfer of surface water or groundwater.

Surface-water appropriations and transfer are governed by laws, some older and others more recent, that are straightforward but numerous, Jess says. Regulations on transfers of groundwater have been left largely to the courts and often are governed by the common law prohibition on transfer from overlying land. However, various exceptions have been set forth by the courts and specific legislation, he said.

In "Geology, Groundwater Chemistry and Management of the Dakota Aquifer in Nebraska," David Gosselin and F. Edwin Harvey, groundwater geologists, and Charles Flowerday, editor, all with CSD and the School of Natural Resources, use groundwater chemistry to assess the history of the water in the Dakota aquifer and explore management issues related to it. The Dakota is a key secondary aquifer, particularly in the eastern part of the state, but its water is fairly to very mineralized. It also may lie under confining layers of shale, clay or silt, which may restrict recharge and require special management strategies, the authors write.

The fact sheet series, called Earth Science Notes, provides four to six pages of timely information on diverse research topics involving Nebraska's natural resources. Copies of Earth Science Notes are available from the Conservation and Survey Division, 113 Nebraska Hall, University of Nebraska-Lincoln, Lincoln, Neb., 68588-0517; e-mail: csdsales@unl.edu or phone (402) 472-7523. Single copies are free; multiple copies are $2 each. If requesting multiple copies be sent by mail, add a $2 fee. Nebraska residents should add city and state sales tax.

Alliance - June 5

Norfolk - June 6

Grand Island - June 10

Beatrice - June 10

North Platte - June 17

Lexington - (date not set)

Ainsworth - June 27

Norfolk - June 30

The clinics offer individual and confidential information and education on farm finances; the laws, regulations and policies governing Farm Services Agency (FSA); debt restructuring and other legal options; and how the mediation program can help work with lenders to find an agreeable and workable solution. Contact the Farm Hotline (1-800-464-0258) to make an appointment and to learn the specific clinic schedule and location for a given town.