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Poor Stands of Cereals - Should You Replant?

May 8, 2003

Joel K. Ransom, NDSU Extension Agronomist for Cereal Crops

Prior to the most recent rains, cereal planting was ahead of schedule for most of the state. The small grains that were planted early have emerged and the early planted corn is just poking through the soil. Reports from throughout the state suggest that most of the winter wheat crop survived the winter and is now starting to develop rapidly. For the crops that have emerged it is now time to assess your plant stand. Poor plant stands can result from a number of factors. Limited soil moisture in parts of the state may have caused poor germination and uneven emergence. Poor quality seed can be the source of poor stands. Diseases, insects and waterlogging can also take a toll on emerging seedlings. For plant stand losses early in the growing season, replanting can be a viable option. The following guidelines should help you decide whether replanting will be more profitable than continuing to manage your "not so good looking crop" (if that is the case).

1. Make an accurate assessment of your stand. A first glance plant stands or early season damage can look much worse than it really is. Moreover, there are times when things are actually worse than they might appear at a distance. If poor emergence or damage is not uniform, focus only on those areas of the field that will likely need to be replanted. For small grains take plant counts from 4 or 5 randomly selected areas (use a 1 square yard quadrant or something similar). For corn, count several randomly selected rows (a 17' 5" in row of corn equals 1/1000 of an acre if 30" rows are used).

Within the range of zero to the optimum number of plants per acre, plant population is highly correlated with yield. If stands are not too low, however, cereal crops do have a remarkable ability to compensate for reductions in plant numbers. Under low populations densities, small grains will put on more tillers and produce larger heads. Corn will produce larger cobs and on occasion produce two cobs when densities are less than optimum. Table 1 describes the minimum plant stand that is needed for a "poor stand crop" to produce as much or more than a replanted crop.

a - Recommended plant populations vary from region to region in the state. As an example, if the target population is 28,000, when populations fall below 16,800-19,600 you should consider replanting.

2. Estimate the yield potential of the replanted crop and the costs associated with replanting. Bear in mind that late planted crops will yield less, sometimes substantially less, than those that are planted in a timely manner. Table 2 provides a rough guide as to the yield reductions that will occur with later plantings.

As indicated in Table 1, fairly large reductions in the "optimum" plant density can be tolerated before it becomes more profitable to replant small grains. For sparse stands, care must be taken to ensure that weeds are adequately controlled. If you do decide to replant, consider the following: When planting after May 20 replant with a higher seeding rate to compensate for the reduced tillering of the later planted crop. After June 1, consider growing the earliest varieties that are available in addition to the higher seeding rate, or consider growing an alternative crop with shorter maturity. Planting small grains after June 21 is not recommended.

Corn, when compared to small grains, is much more sensitive to reductions in plant populations as can be noted from Table 1. The timing of replanting is also critical with corn, so that decisions on replanting should be made as soon as it is practical to fully assess the plant stand of your crop. For corn when replanting after May 20^th earlier maturing hybrids should be planted (how much earlier will depend on the actual date that you will replant). After June 1 corn for grain should probably not be planted except in the southeastern corner of the state where the latest date of planting should be June 10^th. In the northern areas of the state, corn replanting should be avoided after May 25^th.

Additional information on replanting can be obtained from the NDSU Extension Service bulletin, "Replanting after Early Season Crop Injury (A-934)" which is also available through the internet (http://www.ext.nodak.edu/extpubs/plantsci/crops/a934w.htm). An additional resource for corn, "Estimating Yield and Dollar Returns From Corn Replanting", is published by Purdue University Cooperative Extension Service can be found at http://www.agry.purdue.edu/ext/pubs/AY-264-W.pdf.

NDSU Extension Service, North Dakota State University of Agriculture and Applied Science, and U.S. Department of Agriculture cooperating. Sharon D. Anderson, Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. We offer our programs and facilities to all persons regardless of race, color, national origin, religion, sex, disability, age, Vietnam era veterans status, or sexual orientation; and are an equal opportunity employer.
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North Dakota State University
NDSU Extension Service