ILSOYADVISOR POST

Agronomy: Soybeans – Fall Fertility Plans

Growers are harvesting corn and soybeans and experiencing surprisingly good yields for a summer plagued by too much rain, too little rain and wacky weather.

But as harvest rolls forward many growers are already thinking about how to prepare for 2017. Some growers will be planting cover crops if they haven’t already. Others will be doing fall tillage, and most will be applying fertilizer or lime.

Historically, the trend has been to fertilize corn and soybeans at once, before the ‘more-valued’ corn crop. That left soybeans to scavenge for what remained (which might not be much). However, there is a trend to fertilize soybeans separate from corn. Of course, that comes with an application cost, but it also means more nutrients are available for the soybean crop.

Soil pH: As you plan fertility for next year’s soybean crop, start with a look at soil pH and try to maintain a level of 6.2 or above. Having a pH of 6.2 or above is important for nitrogen fixation as the rhizobia bacteria don’t like an acidic pH. A fall application is critical because lime has to dissolve and reach into the soil to raise pH. Most growers apply lime once every 3 or 4 years in the appropriate amounts.

Track Yield: Every bushel of soybeans you harvest removes many pounds of nutrients and draws down the soil reserves. It is good to be reminded how much P (phosphorus) and K (potassium) is removed by a 60 bushel crop: about 44 lbs. phosphate and 71 lbs. potash per acre. That’s a lot and it needs to be replaced after harvest. If you have a 70 bushel goal, your soybeans will need 58 and 94 lbs. available phosphate and potash. You need to know if it’s available and at least apply a portion of that amount.

Soil Test: Growers should soil test every few years to get an idea of how much P and K are in the bank and ultimately try to build the bank so that it is in the moderate/medium category. In stress years it is difficult for roots to access enough nutrients to meet their needs, so keeping soil test levels at the medium level creates the opportunity for the crop to really respond in marginal years. If soil tests are medium or lower, plan to apply the removal rate based on your yield goal. If soil tests levels are high or above, you can probably cut back a bit to save money.

Soil Health: Soil health is not just popular, it is also important to the sustainability of your farmland. If you are not already thinking about soil health and starting to track it, now is a good time to start. You fertilize the soil to feed the crop. It’s time to manage and treat the soil to feed the microbes that make a healthy and productive soil – the key to high, sustainable yields. Many commercial laboratories already offer this service. If you haven’t done so, get a soil health done and use it as baseline to develop a strategy to improve it.

Agronomist Dr. Daniel Davidson posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com or leave a comment below.


Dan Davidson
Soybean agronomist Daniel Davidson, Ph.D., posts blogs on topics related to soybean agronomy. Feel free to contact him at djdavidson@agwrite.com or ring him at 402-649-5919.


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