Title: Rice & Advice, Ep. 01: Rice Seeding Rate Decisions (3/30/21) J. Hardke

Arkansas Row Crops Radio, providing up to date information and timely recommendations on Row Crop Production in Arkansas.

Jarrod Hardke: Welcome to Arkansas Row Crops Radio. IÕm Jarrod Hardke, rice extension agronomist for the University of Arkansas System Division of Agriculture. Today on Rice and Advice weÕre going to discuss rice seeding rate decisions. With that IÕd like to open up with a few general thoughts on seeding rates, a few comments, our standard recommendations for seeding rates for rice, for varieties, pure line cultivars, thirty seed per square foot when weÕre on sit loam soils thatÕs traditionally going to be seventy to eighty pounds per acre depending on the variety and for hybrids thatÕs going to be ten seed per square foot on silt loams and that can range from twenty two to twenty four pounds of seed per acre. Traditionally we do recommend increasing our seeding rate by twenty percent when we move from a silt loam to a clay soil, so that would leave you in the neighborhood of thirty six seed per square foot for variety vs twelve seed per square foot per hybrid. We also have other standard seeding rate increase recommendations regarding seeding method, broadcast, broadcast water seeding, itÕs twenty to thirty percent increase, seed bed preparation. The poorer it is the more you should increase that seeding rate. Somewhere to the tune of ten to twenty percent and then seeding data for extremely early a ten percent increase for extremely late twenty per cent increase. All that having been said, thereÕs a lot of percentage increases in there, but at the end of the day weÕre talking about not exceeding a fifty percent increase when we talk about a standard, for instance on a variety of thirty seed per square foot. We really donÕt ever want to exceed a forty-five to fifty seed per square foot seeding rate. Just keeping that in mind those things are additive but only to an extent. So most of the increases weÕre talking about here are based on traditional seeding rate research that in particular is worth noting was usually done without the use of any form of seed treatments. Newer seeding rate work in the last five to ten years, in that neighborhood, has really been conducted using both insecticide and fungicide seed treatments. With those two things in play, the odds of achieving a greater stand are possible with less seed where limiting stand reductions due to grape colaspius and rice water weevil. WeÕre also limiting stand reductions due to the seedling of these complex by having these things there. However old and new seeding rate studies, traditionally youÕre getting planted into well prepared soils most of the time, so thereÕs not more questionable soil conditions at the time. Sub-optimum stands or where we donÕt have enough plants are always going to be at risk of not being able to achieve our maximum yield potential. ThatÕs not news to anybody but at the same time the excessive stands where we end up with too many plants are at risk for having greater disease, increased lodging and then again weÕre preventing that maximum yield potential in that situation. So our goal is really of course to find that middle ground. We donÕt want to have too little, we donÕt want to have too much, but how are we going to figure out or gauge what that correct middle ground is with everything going on in the field. One way to potentially do that is to look at the results from seeding rate studies through both yield and net return to perhaps give us the best gauge for what our optimal seeding rates could be. And when we look at some seeding rate data from the past several years, one example certainly looking at data from Diamond for example. When you talk about seeding rates at ten seed per square foot, thatÕs only twenty three pounds all the way up to fifty seed per square foot, which is one hundred sixteen pounds. You do see that the yields really keep going up, especially to around forty seed per square foot, which is around ninety pounds and might suggest if you just looked at the yield that the seeding rate may need to be higher and this is average across mostly silt loams, but some clay soil sights mixed in here as well and you see that general increase, but if you flip that around, then look at the net return where again all your other production costs are remaining the same, just the seeding rate part of it, that really from anywhere near that thirty seed per square foot, about seventy pounds on up that thereÕs times you may, sure you can show a little bit more net return, but itÕs pretty flat, there doesnÕt seem to clearly show a great advantage in that situation. Another example, Titan, medium grain, similar story. Yields do generally continue up with a little bit higher seeding rate, but itÕs actually a little bit more flat lined across lower in that thirty seed per square foot range without a great increase going up, so certainly you would expect with that being kind of a flat line, down around thirty seed per square foot in that neighborhood, which for Titan is actually going to be about eighty pounds of seed, youÕre going to see pretty consistently your top net return and some of the seeding rate that actually leans towards slightly lower for it on seeding rate. So we actually may have more risk with Titan of going too heavy in that scenario, so again every variety cultivars going to be going to be a little different. CLL15 we can throw in there. ItÕs a pretty good flat line across the years that thirty seed per square foot, looks like a really good sweet spot going above not showing an increase in yield. Maybe slightly more consistency going a little higher but in general not getting a lot there and when you look at it through the net return portion of it, staying down toward the thirty seed per square foot and not trying to climb much higher definitely giving us a lot better in the net return department. Those are several different variety examples to certainly put a hybrid example in here and that kind of seeding rate trials evolves a little bit over the years looking at hybrid so weÕll talk about it in terms of pounds per seed per acre for a moment because thatÕs how a lot of that was originally conducted before we started shifting more to the seed per square foot. Metrics have kind of converted some of that over and so weÕve got ten, fifteen, twenty, twenty five and thirty pounds of seed per acre. That ten seed per square foot we recommend is about twenty two pounds so that exact rate doesnÕt exist here and what IÕm discussing is really twenty pounds. But you see right there from a yield standpoint thatÕs where you can kind of more consistently hit top end yield. To be really consistent itÕs clear we need to be a little higher so again that twenty two pounds is probably going to continue to be that spot we need to be in and when you look at it from the net return side of it the same is true that yes the yields may be slightly continued up to more consistent that net return isnÕt necessarily there going up above that so that twenty two pound range still looks like where we need to be. Again you start moving much lower than that, certainly below the twenty pound mark and itÕs getting a lot more inconsistent from a yield and net return standpoint.

So just kind of some take home messages, our current optimum seeding rate recommendations for silt loam soils may be the best middle ground option for most scenarios. Our newer planting equipment, even on clay soils, is in general producing greater stands than kind of our planting technology of the past and it seems to be minimizing the need for some of the traditional seeding rate increases that we still point to a lot. However, every field situation is different, so weÕre still going to need to be looking to make adjustments based on trying to achieve proper seed depth, seed to soil contact and furrow closure. Again the trials weÕre talking about are traditionally planted into very good, very well prepared seed bed conditions, so thatÕs one area in particular that the rougher the seed bed is the more we need to consider increasing that seeding rate some over the standards look to be really good middle ground to make sure that we have an adequate minimum plant stand. ThereÕs always going to be fields with poor stands for any number of reasons that can come up, but spending consistently more money on seed for every single rice field youÕve got just trying to avoid having that one single field with a low stand is probably not the best approach. In a lot of the low stand fields we get into having just a little bit more seed out there is probably not going to be the answer to that field or still allow us to have maximum yield potential in that situation.

At the end of the day the goal is to get a seeding rate that for variety will give us somewhere in the neighborhood of twelve to eighteen plants per square foot and for a hybrid we want to end up with five to eight plants per square foot. And thatÕs as our final stands in the fields. Those are the ranges that give us maximum yield potential without flirting with a little too low that again will just keep us from ever having a chance to get the top end yield or going too high that will bring in more problems that could prevent us from getting there. So based on your experience with your fields and your equipment, letÕs adjust our seeding rates as necessary to achieve those plant stands. Twelve to eighteen plants per square foot for varieties, five to eight per square foot for hybrids and thatÕs going to give us the best chance at maximum yield potential regardless of what weÕre planting and when. But again paying close attention to those soil conditions and the likelihood of achieving very good stands in those scenarios. 

With that, the research and work IÕm referring to is supported by the Arkansas Rice Checkoff made possible by Rice Growers of Arkansas as well as the University of Arkansas System Division of Agriculture. Thanks for joining us for this episode of Rice and Advice on Arkansas Row Crops Radio. 

End notes: Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information please contact your local county extension agent or visit uaex.edu.