Factors to consider when making replant decisions in wheat include: stand uniformity, actual stand compared to the target stand, replanting date, weed control, and insurance cutoff date. The following information was provided by Romulo Lollato, K-State Wheat and Forages Specialist.
• Stand uniformity. Easily recognizable patterns occur in the field based on soil water drainage and accumulation when excessively moist soils cause poor wheat emergence. In this case, stands might be relatively uniform in better-drained areas but non-existent in poorer-drained areas, leading to a high within-field variability. Producers should have as top-priority replanting those large areas with poor emergence once conditions for fieldwork allow. If stand is patchy in areas that already emerged, producers should also consider replanting at lower seeding rates to bring final population closer to the desired stand, as discussed below.
• Actual stand compared to the target stand. In areas that already emerged despite the excessive moisture, stands might also be suboptimal and thinner than desired. In these situations, it is often helpful to compare the actual stand with what desired plant populations was to meet our yield goals. Table 1 shows the number of target plants per row foot based on seeding 60 lb/ac, (to see the full table go to www.cottonwood.ksu.edu) depending on seeding rate, seed size (provided with certified seed), and row spacing, and considering 80 percent emergence. If seed size is not known, 14,000 to 16,000 seeds per pound can be used for most wheat varieties in Kansas, except those with rather large or small kernels. To determine the average number of plants per foot of row, several random plant counts across the field should be taken, given a uniform emergence throughout the field. If the average number of plants is about 50 percent or more of normal and the stand is evenly distributed, the recommendation is to keep the stand. Wheat’s tillering ability can greatly compensate for poor stand provided soil fertility is adequate and the weather is favorable. With less than 40 percent of normal stand, the recommendation is to replant the field. If possible, replanting should be done at a 45-degree angle to the original stand to minimize damage to the existing stand.
Recent K-State research indicates that approximately 900,000 emerged plants per acre are needed for most varieties to maximize yields under normal fertility conditions in Kansas. Thus, if producers are not aware of their target plants per row foot, the above threshold might be a good goal for central Kansas producers.
• Replanting date and seeding rate. As of late October, most of the state is past the optimum sowing date, maybe with the exception of south-central Kansas. For portions of the field with no stand established, where the entire stand will need to be replanted, producers should plan to increase their seeding rates by 10-15% for every week past the optimum sowing date. Producers should consider replanting if a fields with: partial stand (50% or less of target stand), highly variable stands, or large areas that have failed. In portions of the field where stand is below optimum, producers can cross-drill at the rate of 30-40 pounds per acre in western Kansas and 40-60 pounds per acre in central and eastern Kansas, using a double-disc opener drill if possible to minimize damage to the existing stand. If the replanting is done in November or later, increase the seeding rates to 60-75 pounds per acre in western Kansas and 75-90 pounds per acre in central Kansas. If stands are less than 30 percent of normal, increase these seeding rates by 20-30 pounds per acre. Treating the seed with a fungicide can help ensure viability in wet soil environments and reduce the risk of additional problems with stand establishment this season.
• Weed control. A thin wheat stand can increase the potential for weed infestations. This was clearly a problem for many fields during the 2017-18 growing season. Therefore, we need to acknowledge that weed control needs to be part of the decision to replant of thicken wheat stands. Moreover, uneven wheat stands can also influence herbicide timing because parts of the field are at development stages. Herbicides such as 2,4-D and dicamba can cause serious crop injury when misapplied. Potential problems due to improper application timing include trapped heads, missing florets, or twisted awns. Accounting for this variability in growth stage within a field can lower the risk of crop injury and loss of yield.
Stacy Campbell is an agriculture and natural resources agent for Cotton Extension District. Email him at scampbel@ksu.edu or call the Cotton Extension District Hays office, 785-628-9430.
