Similar to the weather conditions we experienced in May of 2019, the extremely hot and dry conditions this week is going to challenge growers to make some difficult planting decisions. Planting in dry conditions without adequate soil moisture in the furrow results in poor or reduced stands which in most cases translates to a significant yield impact. Based on their specific situation, there are couple different strategies that growers may utilize for planting in dry conditions – dusting in cotton and hoping to catch a light rain or planting deeper than normal seeding depths to chase soil moisture. Both of these planting strategies require very careful consideration to planter depth and downforce adjustments as emergence issues due to improper planter setup are usually more common and apparent when planting cotton in less than ideal field conditions. Here are few points to consider based on the research studies conducted at UGA as well as the visual observations made during planting in similar dry field conditions in the past:
Dusting in Cotton: In general, most planters (even brand new) have some seed depth variability among the row-units which is hard to notice when planting cotton at nominal seeding depths (0.5 – 1.0 inch). However, when dusting in cotton or planting at depths shallower than 0.5 inch, these seed depth variations can influence emergence significantly in some cases. The picture below shows an example of the center two rows on a 4-row planter where the seed depth setting on each row-unit was set similarly to plant seed at 0.5-inch deep with no downforce so technically simulating a “dusting in” scenario. While you can notice a decent cotton stand on the right, there are no emerged plants at all on the left side due to the lack of correct seed depth setting on that particular row-unit even when it was set the same as other row-units. In fact, if you look closely, you can still see the seeds laying the ground (red circles) two weeks after planting. The main point here is that ensuring correct seed depth on every planter row-unit is critical when planting at shallower depths or dusting in cotton and making appropriate adjustments as needed to each row-unit separately as any deviation from target seeding depth in these situations will clearly show up in emergence.
Planting Deeper than 1-inch Seed Depth: Generally, it is not recommended to plant cotton seed deeper than 1-inch as cotton seed requires a lot of energy to germinate and most of its energy reserves can be used (or sometimes depleted) before it emerges out of the soil. When planting cotton seed deeper than 1 inch in dry soil conditions, planter downforce can further impact emergence as a higher downforce can result in both soil compaction around the seedbed and even deeper seed depth than desired, which significantly reduces the likelihood of that seed’s emergence. The picture below shows an example of reduced and uneven emergence in both rows when cotton was planted at 1.5-inch seeding depth using a higher downforce of 200 lbs in dry soil conditions and loamy sand. Remember that the exact downforce requirements will vary based on soil type and texture but make sure you are digging behind the planter to verify if the seed is placed in a firmer seed bed and is not compacted or pushed deeper than the target seeding depth. Based on the in-field assessment, make appropriate downforce adjustments for your soil type and texture to attain desired seed placement.
Planter research studies conducted at the University of Georgia also indicated that the large-seeded cotton varieties tend to perform better than the small-seeded varieties in situations where cotton seed is placed deeper or planted using a higher downforce. Therefore, cotton growers who prefer to plant small-seeded varieties needs to be extra careful about planter depth and downforce settings when planting in dry soil conditions.