Peanut Grower Magazine Column Peanut Notes No. 11 2020

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As we move toward plantings in 2020, remembering some of the basics is important. With farmers having more acres to manage, taking care of details that can limit yield can be easily overlooked. Soil pH is one of the “silent killers” when it comes to yield, especially with respect to peanut. The optimum pH range is 5.8 to 6.2. In a recent survey of soil samples sent to the N.C. Department of Agriculture & Consumer Services, a little over half of the samples fell in this range. Most of the remaining samples were equally split between a pH greater than 6.2 and pHs between 5.4 to 5.7. About 5% of samples were below pH 5.4. Using historical yield data from research plots, the economic value of adjusting pH from about 5.3 to 5.8 at state average yields (2 tons), a price of $535/ton, and cost of lime at $42/ton, was about $200/acre. This equated to an 11:1 return on lime investment, even when all of the lime cost was charged to peanuts. Having soil pH in the optimum range also increases the likelihood of getting a positive response to applied gypsum and Bradyrhizobia for nitrogen fixation. A second basic is establishing good rotation sequences for peanuts. More years of corn or cotton and fewer years of soybean often result in greater peanut yields. If you need soybeans for overall farm profitability, plant soybeans right after peanuts and then get at least 3 years of cotton, corn or grain sorghum in the rotation prior to peanut. Sweetpotato is a great rotation with peanuts while tobacco is less than ideal but better than soybeans. Our tools are limited in their ability to overcome poor rotations. Disease-resistant varieties can help and some commercial products can suppress nematodes and disease. But these approaches can result in inconsistent results. And, we do not have a Virginia market type with resistance to nematodes. While the economics of the rotation crop will almost always outweigh the impact of the overall rotation sequence, at some point a less than ideal rotation sequence will affect peanut yield or require greater input costs. From a weed management standpoint, using more residual herbicides upfront (preplant in conservation tillage, preplant incorporated in conventional tillage, preemergence in both tillage systems, and early postemergence), being timely with postemergence sprays, rotating modes of action, and pulling up escaped weeds to prevent seed production are important elements of successful weed management strategies in peanut. Pay particular attention to common ragweed and Palmer amaranth in the V-C Region. We have ALS resistance in both weed species and suspect PPO resistance in some areas. If you had a strong PPO-herbicide program and these weeds escape, please be diligent in keeping them from seeding out. Start out with clean fields in both conventional and conservation tillage production – it makes for a long summer when we have to start catching up when peanuts are emerging.