Preplant Manure and Commercial P and K Fertilizer Effects on Alfalfa Production

Abstract

Many dairy producers are being forced to consider applying manure onto their alfalfa ( Medicago sativa L.) acres because of environmental concerns regarding overapplication of manure on their corn ( Zea mays L.) acres. We compared the use of manure and commercial fertilizer prior to establishment on alfalfa herbage yield and nutrient concentrations. Three rates of manure (3 000, 6 000, and 12 000 gal/acre) were broadcast and incorporated before the direct‐seeding of alfalfa. Three commercial fertilizer treatments also were applied to provide P and K application rates similar to those in the manure. At all sites, establishment‐year yields from the manure and fertilizer treatments were equal to, or greater (0–103%) than, the control yield. With “very high” soil P and K tests, production‐year yields were similar for the manure and fertilizer treatments. The responses to fertilizer and manure treatments were similar on the “medium”‐testing soil where yields were increased with increasing nutrient rates. Herbage P concentrations were generally not affected by fertilizer or manure additions, while herbage K concentrations were increased in direct proportion to the rate of manure or fertilizer applied at all sites. Preplant manure applications resulted in alfalfa yield increases similar to commercial fertilizer additions where fertilizer would be recommended and was not detrimental to alfalfa production. Research Question Livestock producers often find themselves in a dilemma: they do not have enough corn acres for spreading their manure at agronomic rates. This requires additional land area to spread manure, and for dairy producers, alfalfa is often the only other crop grown. Because alfalfa requires high amounts of P and K for optimum production, supplying these nutrients with manure could be economically feasibly sound. This study compared preplant manure applications with preplant fertilizer applications for alfalfa forage production and nutrient concentrations on soils testing “very high” and “medium” for P and K. Literature Summary Fertilizer recommendations in most states do not encourage the use of manure on alfalfa because alfalfa can produce its own N and the manure N would be used more efficiently on nonleguminous crops. A few states, however, recommend some fertilize N for alfalfa seedings under limited conditions, such as coarse‐textured or low organic matter soils. Studies that have been conducted on preplant manure applications to alfalfa have not shown a consistent positive or negative effect. Study Description Soil and manure properties associated with each site are listed in Table . Treatments are listed in Table . Manure and fertilizer rates were selected to bracket the predicted requirements for 2 yr of alfalfa. All preplant treatments were incorporated with tillage equipment. Following EPTC herbicide incorporation, Pioneer 526 alfalfa was direct seeded at 15 lb/acre at all sites. One or two cuttings were made during the seeding year and four cuttings were harvested in the production year. Applied Questions What effects did the treatments have on herbage dry matter yields? Yield and appearance at the first cutting in the establishment year make a lasting impression on crop producers. Manure treatments generally increased establishment year yields compared with the unfertilized control, whereas fertilizer treatments consistently increased yield only when the soil tests were “medium.” Production‐year yields increased with increasing manure rates on both soil types (Fig. ). The increase was much more dramatic where soil P and K tests were categorized as “medium.” The yield responses to the fertilizer treatments were similar to the manure treatments only on the medium‐testing soils. Do fertilizer/manure treatments have an effect on herbage nutrient concentration? Herbage N concentrations did not vary due to the imposed treatments except at the medium‐testing P and K site in the production year. This is not surprising because alfalfa can get its N directly from the soil or indirectly from the atmosphere. Phosphorus concentrations measured in herbage from the first cuttings each year were not consistently affected by the imposed treatments (Table ). Herbage concentrations of K increased according to the rate of K applied for either nutrient source (Table ). Recommendations Either manure or inorganic fertilizer can supply the nutrient requirements of an alfalfa crop when soil tests indicate a probable response. There were no consistent differences between the two nutrient sources with regard to the N, P, and K composition of the forage. These results suggest that preplant application of manure is a viable option for manure use by livestock producres with limited acrages of corn, or other cereal grains, available for manure application. The concern of detrimental effects of manure applied onto alfalfa ground were not realized in this study. Care must be taken to have a good seedbed, avoiding situations (i.e., applying manure to wet soils) that would lead to compaction zones. Miscellaneous properties and information associated with the study. Rosemount South North Waseca Soil type Waukegan sil Waukegan sil Nicollet cl Manure source Swine Swine Dairy Manure analysis 77 + 5 + 32 75 + 7 + 25 36 + 6 + 19 lb N + P + K/1000 gal Soil P test, ppm 35 (VH) 30 (VH) 8.5 (M) Soil K test, ppm 230 (VH) 200 (VH) 94 (M) Nutrient sources and application rates at Rosemount and Waseca. Site Treatment Nutrient source Rosemount‐South Rosemount‐North Waseca ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ N + P + K, lb/acre ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ Control None ‐‐ ‐‐ ‐‐ Manure low Manure, 3 000 gal/acre 231 + 16 + 95 159 + 20 + 75 108 + 19 + 57 medium Manure, 6 000 gal/acre 462 + 32 + 189 318 + 40 + 149 216 + 40 + 115 high Manure, 12 000 gal/acre 924 + 63 + 379 636 + 79 + 299 421 + 74 + 229 Fertilizer low Fertilizer 0 + 40 + 57 0 + 40 + 57 0 + 15 + 57 medium Fertilizer 0 + 79 + 115 0 + 79 + 115 0 + 29 + 115 high Fertilizer 0 + 158 + 229 0 + 158 + 229 0 + 58 + 229 Effect of preplant nutrient application on first cutting P and K concentrations for all site‐years. Treatment P K ‐‐‐‐‐ % ‐‐‐‐‐ Control 0.29 1.70 Manure low 0.30 1.90 medium 0.31 1.95 high 0.31 2.11

Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗

The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.