Dry Spring Conditions: Considerations Before Deciding to Replant

DS-6-97, May 2003
Joel K. Ransom, Extension Agronomist - Cereal Crops
 

Dry spring conditions can have a significant effect on the emergence of crops, resulting in poor stands. If planting was early but was emergence was poor due to inadequate soil moisture, replanting can be a viable option if it looks likes future rainfall and current soil moisture will support a new crop.   Often leaving the crop that has a poor stand can be the best scenario. Any established plants have the advantage of a developed root system that can access subsoil moisture and consequently have the greatest chance of producing a crop. Under dry conditions any crop can also be considered a potential source of forage.  The following guidelines should help you decide whether replanting will be more profitable than continuing to manage your Anot so good looking crop@ (if that is the case).

Factors to consider before replanting.

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 Apoor 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 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.

 Notes for small grains

As indicated in Table 1, fairly large reductions in the Aoptimum@ 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.

Notes for corn

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 20th 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 10th.  In the northern areas of the state, corn replanting should be avoided after May 25th.

Herbicide residues

If replanting is to be done, consideration should be given to herbicide residues from the previous crop if you plan to alter the crop.  The accompanying table provides information on replanting options following the use of various herbicides. Consult the herbicide label recommendations on tillage, planting depth, and interval between herbicide application and replanting. The current North Dakota Weed Control Guide (circular W-253) can be consulted to address most questions or options.

Crop choices for replanting fields previously treated
with herbicides that have crop rotation restrictions.

*For additional information refer to the North Dakota Weed Control Guide, Circular W-253.