AGRICULTURE NEWSLETTER By: Katelyn Barthol March 2017

TopicsTopdressing Wheat with SulfurGrowing Wheat and WildfiresSoil Temperature and VegetablesPruning Deciduous ShrubsCalenderUpcoming Events

Topdressing wheat with sulfurIn recent years,

sulfur (S) deficiency inwheat has becomecommon in many areasof Kansas, particularly inno-till wheat. Classic Sdeficiency symptoms,confirmed by soil and

plant analysis, have been observed in many no-tillwheat fields during periods of rapid growth in thespring. These observed deficiencies generally occurduring periods of rapid growth prior to joining, orduring stem elongation.

There are two likely reasons for this: a reductionin sulfur additions to the crop from atmosphericdeposition and phosphorus fertilizer applications, andcooler soil temperatures as a result of no-till planning,which slows S mineralization in the soil. The net effectof these factors is a significant reduction in the cropavailable S.

Generally the S-deficient wheat is yellow andstunted, and the problem is found in patches in thefield, especially in areas where there has been previoussoil erosion or soil movement. Sulfur deficiency ongrowing crops is often mistaken for nitrogen (N)deficiency. However, unlike N where the older leavesshow firing and yellowing, with S deficiency, the paleyellow symptoms of S deficiency often appear first on

the younger or uppermost leaves. Wheat plants withS deficiency often eventually become uniformlychlorotic. The patchy S deficient areas of the field areoften found on hilltops or side slopes where erosionhas occurred and soil organic matter is reduced, orwhere leaching is more pronounced. In terraced orleveled fields, wheat in areas where topsoil wasremoved or significant cuts were made alsocommonly shows symptoms.

Sulfur deficiencies in wheat have been showingup early in the spring, shortly after green-up, beforeorganic S is mineralized from soil organic matter, andbefore wheat roots can grow into the subsoil toutilize sulfate accumulated there. Deficiencies of Sare often difficult to identify because the paling incrop color is not always obvious. Crops lacking Salso may be stunted, thin-stemmed, and spindly. Inthe case of wheat and other cereal grains, maturity isdelayed. Due to the slower growth and lack of good tillering, winter annual weed competition is alsoenhanced.

The majority of S in soils is present in organicforms in surface soils and as sulfate. Sulfate isrelatively soluble, so it tends to leach down from thesurface soil into the subsoil. In many of our Kansassoils it will accumulate in the B horizon in two forms.Some will be sorbed to clay surfaces and coatingssimilar to the processes whereby phosphates aresorbed, though sulfate will not be absorbed asstrongly. Sulfate will also be present in the subsoil ofmany Kansas soils as gypsum. Traditionally, Sdeficiency was most common on high-yielding cropsgrown on irrigated sandy soils low in organic matterand subject to leaching. However, due to the reducedadditions from the atmosphere (there is less S in theair now) and continued crop removal, an increasingnumber of finer-textured soils have shown Sdeficiency in recent years.

A soil test for available sulfate-S in the soil profileis available. For proper interpretation of this test, soilorganic matter, soil texture, the crop to be grown, andthe expected yield level all need to be factored in.Since sulfate-S is mobile, sampling to a 24-inch depthis important. Accurate estimates of S needs cannot bemade from a surface sample alone. However, due tothe relatively high demand for S during the rapidvegetative growth phase of wheat growth, andrelatively shallow rooting by the wheat crop at this me, the S measured in the deeper, subsoil levels bythe test may not be available to wheat in the earlyspring, especially where soils are cold.

Many fields in North Central and NortheastKansas now have an established history of Sdeficiency for wheat. In this situation rather thanwaiting for symptoms to appear in the spring, farmersmay want to consider a winter top-dressingapplication of S as a preventive measure. There aremany S-containing fertilizer materials. Several drymaterials are available that can be blended with dryphosphorus or nitrogen fertilizers for winter/springtop-dressing. Some of these products are best used inpreplant applications, however.

Growing Wheat and WildfiresWheat can be injured

by fire or super-heatedair, and this injury will bemost severe on the edgeof the field closest to theheat. Wheat in the joiningstage or beyond is in

greater danger as the growing point is above ground,but wheat in the tillering stages of growth can alsosuffer consequences of extreme heat. It is notuncommon to have some injury to growing wheat onthe edge of a field if the field is adjacent to aprescribed burn. The injury symptoms may bebleached or scorched leaves and possibly damagedgrowing points. The extent of injury from a wildfiredepends on how quickly the fire moved through thefield or around the field.

Research has found that the lethal hightemperature for wheat is about 120 degrees F. Wheatexposed to temperatures above this threshold willmost likely not recover. A wildfire can easily heat theair or the plants themselves to temperatures wellabove that level, depending on the distance of the firefrom the wheat, possibly resulting in irrecoverabledamage to the affected plants.

Soil Temperature and Vegetables One of the most neglected tools for vegetablegardeners is a soil thermometer. Soil temperature is amuch better measure of when to plant than airtemperature or the calendar. Planting when soil is toocool can cause seeds to rot and transplants to sit there. A number of vegetables can germinate and grow atcool temperatures. For example, peas will germinateand grow well at a soil temperature of 40 F. Thoughlettuce, parsnips, and spinach can sprout at a soiltemperature of 35 F, they prefer at least 45 F for bestgermination and growth. Radishes also do well at asoil temperature of 45 F. Warm-season crops such astomatoes, sweet corn and beans prefer at least 55 Ffor germination (or transplanting), but others such aspeppers, cucumbers, melons and sweet potatoes needit even warmer, about 60 F. Taking soil temperature accurately is a bit of ascience. First, use a metal soil thermometer, which issold in many garden, auto parts and hardware stores.Take temperature 2.5 inches deep at about 10 to 11a.m. Temperature variations throughout the day andnight affect soil temperature, with lowest readingsafter dawn and warmest around mid-afternoon. Thelate-morning reading gives a good averagetemperature. If taking the soil temperature at thistime is not practical, take a reading before you leavefor work and a second when you return home anduse the average. Also be sure to get a consistentreading for four to five days in a row before planting,and make sure a cold snap is not predicted. An excellent guide sheet on this subject is publishedby the Alabama Cooperative Extension System and istitled “Soil Temperature Conditions for VegetableSeed Germination.” It can be found athttp://www.aces.edu/pubs/docs/A/ANR-1061/ANR-1061.pdf (Ward Upham, KSRE Rapid Response Specialist)

Pruning Deciduous ShrubsGardeners are eager to

get out and do somethingin the landscape this timeof year. One chore that canbe taken care of now ispruning certain shrubs.Often, gardeners approachpruning with trepidation,but it is not as difficult as it

may seem. Remember, not all shrubs need to bepruned (i.e., witch hazel), and certain shrubs, whichwill be identified later, should not be pruned this time

of year. Shrubs are pruned to maintain or reduce size,rejuvenate growth, or to remove diseased, dead ordamaged branches. Deciduous shrubs are those thatlose their leaves each winter. Evergreen shrubsmaintain foliage all year and include yews andjunipers.

Deciduous shrubs are placed into three groups:- Those that flower in the spring on wood

produced last year- Those that flower later in the year on current

seasons’ growth; and- Those that may produce flowers, but those

flowers are of little ornamental value.Shrubs that flower in the spring should not be

pruned until immediately after flowering. Thoughpruning earlier will not harm the health of the plant,the flowering display will be reduced. Examples ofthese types of plants include forsythia, lilac and mockorange. Shrubs that bloom on current seasons’ growthor that do not produce ornamental flowers are bestpruned in late winter to early spring. Examples includeRose-of-Sharon, pyracantha, Bumald spirea andJapanese spirea. Pruning during the spring allows wounds to healquickly without threat from insects or disease. Thereis no need to treat pruning cuts with paints or sealers.In fact, some of these products may retard healing.There are three basic methods used in pruning shrubs:thinning, heading back and rejuvenating. Thinning isused to thin out branches from a shrub that is toodense. It is accomplished by removing most of theinward growing twigs by either cutting them back to alarger branch or cutting them back to just above anoutward- facing bud. On multi-stemmed shrubs, theoldest canes may be completely removed. Headingback is done by removing the end of a branch bycutting it back to a bud and is used for either reducingheight or keeping a shrub compact. Branches are notcut back to a uniform height because this results in a"witches-broom" effect. Rejuvenation is the most severe type of pruning andmay be used on multi-stem shrubs that have becometoo large, with too many old branches to justify savingthe younger canes. All stems are cut back to 3 to 5inch stubs. This is not recommended for all shrubs butdoes work well for spirea, forsythia, pyracantha,ninebark, Russian almond, little leaf mock orange,shrub roses and flowering quince. (Ward Upham,KSRE Rapid Response Specialist)

CalenderMarch

6th: Meet & Greet our new FACS Agent 4 p.m.- 6 p.m.11th: 4-H Beef Tagging21st: Soil Moisture Sensor Field Demonstration @ Roth Farms25th: Finney County Pig & Goat Sale

Upcoming Events: