Fertilizer is a major investment for any farmer. It’s also an important decision to make, because the wrong amount of fertilizer can actually harm your soil and crops. If you’re looking to grow soybeans, the first thing you’ll need to do is determine how many pounds of fertilizer per acre you will need.
It’s important to note that there are different types of fertilizers on the market today, including organic, synthetic and chemical fertilizers. Organic fertilizers are derived from animal or plant waste; chemical fertilizers are made from inorganic substances such as sulfuric acid; and synthetic fertilizers are manufactured using chemical reactions that cause organic nitrogen compounds like ammonia or urea to be converted into nitrates or ammonium salts that plants can absorb through their roots.
When it comes to growing soybeans, there are two primary types of nitrogen sources: those derived from natural gas (which includes liquid ammonia) and those derived from petroleum products (such as urea). Urea-based nitrogen sources tend to be more expensive because they require less processing than other kinds of nitrogen sources for use in agriculture.
The most common question in this field is “How much fertilizer should I use on my soybean crop?” The answer depends on many factors, including the soil’s nutrient content, the type of crop being grown, and the crop’s desired yield. In general, soybeans need about 85 pounds of N per acre to grow well. While this amount may seem excessive, it is the most common nitrogen source available to soybeans.
Nitrogen
One of the most commonly asked questions about fertilizing soybeans is, “How much nitrogen per acre should I use?” Depending on the cultivar, a bean may need anywhere from four to five pounds of nitrogen per bushel. However, it is important to understand that soybeans fix only about half of the nitrogen they need. If your crop yields less than 20 bushels per acre, you may want to consider reducing your nitrogen credit.
If you grow soybeans for higher yields, the amount of nitrogen you need is much higher. This crop needs four times as much nitrogen per bushel as corn. A typical soybean crop should get about four pounds of N per bushel. That means that if your crop yields fifty bushels per acre, you’ll need 240 pounds of nitrogen per acre. However, if you have a well-managed, irrigated crop, it could grow as high as eighty bushels per acre.
When applying nitrogen fertilizer to soybean crops, it is important to consider the yield potential of your crop and the likelihood of burning leaves. A low rate of nitrogen can be applied in alternate strips on a few acres, while a higher rate can increase yields. Precision farming techniques have made this possible, and now you can evaluate fertilizer application field by field. And don’t forget to measure your soil’s nitrogen pool before applying any nitrogen.
To plant a soybean that will yield 40 bushels per acre, you need to use 200 pounds of nitrogen. This is because legumes are nitrogen-fixing plants and require a special N-fixing bacterium. Most legume inoculants for crops do not work on soybean. If you’d like to grow a soybean that has active N-fixing bacteria, inoculate the seeds with Bradyrhizobia japonicum. Look for bright pink nodules on the roots, which are the result of the inoculation process.
Phosphorus
Depending on the soybean variety, the amount of N you apply to your soil can have a significant impact on how much yield you can expect. In Nebraska, for example, a soybean yield of 50 bu/acre meets approximately 50% of the soybean’s N needs. If your yield is higher than that, it may require as much as 60 lbs N per acre. But because of the wide range of environmental conditions in the region, it’s difficult to predict the exact amount of fertilizer you’ll need. Generally, soybeans need an additional 20 pounds of N per acre of soil in order to grow to their potential.
Soil pH is an important factor in determining how much fertilizer to apply. Soil pH can vary across soybean production regions. Some soybean soils may be naturally low in P and not require additional fertilizer. Soil pH levels should be checked periodically and adjusted according to the soil pH. When applying fertilizer, remember to take into account the amount of phosphorus and potassium your soil contains. If your soil pH is lower than 7.4, you may want to apply additional fertilizer to compensate for the phosphorus and potassium that soybeans remove.
In addition to nitrogen and phosphorus, soybeans also need magnesium. A magnesium deficiency in soybean crops first manifests as pale leaves with purple or red spots on the leaf. Soybean production in high-yielding environments requires high fertilization rates to maximize yields. Too little fertilizer will result in low soil test levels and a decreased yield. The application rates for soybeans should be based on the soybean crop’s total nutrient needs.
Potassium
To understand why potassium is so important to soybean production, we must first look at its uptake by the plant. Like cotton, soybeans are relatively high in K. However, their uptake of K is limited, especially during certain periods. The most accurate way to determine K requirements for soybeans is by testing the soil. If the potassium level is low, fertilizing with potassium is recommended. However, potassium should not be placed in contact with the soybean seeds, as it may cause salt injury. Potassium increases yields significantly, often greater than P.
In 2017 researchers from the University of Minnesota established long-term research trials to determine if potassium was necessary for soybeans. These trials took place in Lamberton, Crookston, Morris, and Waseca. Researchers applied potash ahead of soybeans in the same fields and measured the yield at various K levels. Results showed that if soybeans were planted in the same fields as corn, potassium levels were sufficient, but the rate of K was not important.
Insufficient K and P nutrition limits the soybean yield potential. For this reason, a progressive nutrient management plan is needed for the best soybean yield. With a proper fertilizer application rate, a soybean yield response can be as high as eleven to 18 bu./acre. Even higher yields have been observed with fertilization rates over ten meq per 100 g. The costs associated with a full application of fertilizer are $0.16 per lb.
To determine the critical K level for your soybean crop, you should multiply the cation exchange capacity of the soil by 2.5 or 75. For a 50-bu./acre soybean crop, the critical level is about 12 meq per 100 g soil. To maintain that level, fertilize every other crop in the same field and then harvest soybeans. If your soil has a K deficiency, your soybeans will display yellowing of the leaf margins, scorching, and dieback.
Molybdenum
Using a molybdenum fertilizer to boost your soybeans’ yield is a common practice, but it has a limited effect. This micronutrient is absorbed primarily by the soil’s carbonates and oxides. If you want to make your soybeans grow better, you should keep the pH of your soil at 6.5 or higher. Soils that are too acidic should be limbed to prevent a deficiency.
Before you apply the fertilizer, take soil test results. The amount of potassium and phosphorus in the soil must remain above a critical concentration, which is the level where ninety-seven percent of your crop yields can be achieved without adding other inputs.
The recommended rate for applying manganese is 2 to 20 pounds per acre. It should be applied as MnSO4. The same is true for using manganese as an ingredient in NPK fertilizers. However, banding manganese sources with acid-forming fertilizers increases its effectiveness. It reduces the rate of oxidation to tetravalent manganese. In addition, it has no residual effects. In addition, lower rates are required for foliar application.
The nutrients required by soybean plants vary based on growth stage. Generally, soybeans have the highest nutrient demand during seed fill. The plant will absorb nutrients in the soil through nitrogen fixation and remobilization of older plant tissue. The nutrients are then used by the soybean plants to support seed development. This process requires high levels of nitrogen and other nutrients. It is important to use fertilizers that contain these nutrients, or else the yield will suffer.
Manure
The application rate for fertilizer in soybeans is based on the yield of the crop and the soil phosphorus recommendations. The total loss of dry matter and associated nutrients is between 61 and 89%, depending on the animal species. To calculate the appropriate application rate, multiply the yield by 3.5 pounds of N per bushel. For soybeans, this would be 210 pounds of N and PAN per acre.
Environmental concerns have arisen over the use of manure in soybean fields. Since soybeans are leguminous plants that fix atmospheric nitrogen, applying supplemental nitrogen may increase nitrate-nitrogen losses and affect water quality. On the other hand, organic amendments can have beneficial effects on soil borne pathogens. For example, if you are applying hog manure to soybeans, the application rate may be twice that.
The risk of nitrate-nitrogen loss is higher early in the growing season than during the growing season, so monitoring soil nitrate levels is critical. However, if the nutrient rate of the manure is 120 pounds per acre, there is no need to worry about mid-season losses. So, when applying swine manure, be sure to consider whether it will help your crops.
Considering the risks and costs of slurry operations, it is important to capture the fertilizer value of manure as well as ensuring that the slurry is applied to the crop ground to minimize commercial fertilizer purchases. Additionally, manure application is associated with some liabilities, making it less valuable than commercial fertilizers. As a result, you need to carefully match the manure application rates with your cropping system in order to reduce the risk of water quality degradation.