Fertilization strategy affects crop nutrient concentration and removal in semi‐arid U.S. Northwest

Abstract

Access to livestock manure is increasing in semi‐arid cropping systems of U.S. Northwest prompting evaluation of fertilization strategies on regional production systems. A study conducted from fall 2012 to 2019 used: fall‐ or spring‐applied dairy manure (56 Mg ha−1), fall‐applied composted dairy manure (33 Mg ha−1), spring‐applied urea or SUPERU (Koch Agronomic Services), and a control (n = 6) on a corn (Zea mays L.)–barley (Hordeum vulgare L.)–alfalfa (Medicago sativa L.)–alfalfa–alfalfa rotation. The effects of fertilization strategies on (a) soil nutrients, (b) crop tissue nutrient concentration and removal, and (c) digestibility and energy content of forages are discussed. Compost and manure additions increased corn silage N, P, K, respectively, by 0.86, 0.28, and 2.4 g kg−1 over other treatments; silage Ca and Mg were depressed 0.4 and 0.53 g kg−1 by manure applications. Barley grain Premoval and Kremoval increased 5.10 and 7.65 g kg−1 under manure applications relative to urea and SUPERU treatments while crude protein (CP) (19.1 g N kg−1) neared limits of high‐quality malt extract (16–19 g N kg−1). Compost and manure increased alfalfa K by 2.3 and 5.5 g kg−1 over other treatments, approaching levels of concern for hypocalcemia in dairy cattle (≥30 g K kg−1). No major impact on corn silage or alfalfa quality parameters, were observed. Present Idaho nutrient removal estimates were representative of corn and alfalfa, but not barley in which observed N removal was 28% lower. In 17 of 18 instances, contrast testing suggested nutrient removal differed under organic amended treatments, suggesting nutrient removal modifiers in production systems receiving organic amendment may need established.

Soil health indicators reveal that past dairy manure applications create a legacy effect

“…With respect to EC, Bierer et al. (2023) found that EC increased due to recent manure applications, but in the present study, we found that after 11 years the EC of the manure treatments was similar to the non‐manure treatment. Because the irrigation water (from the Snake River) used in this study is relatively low in salts, any salts added in manure will be leached over time.…”

“…Studies in Idaho have shown that dairy manure generally does not increase soil pH due to the high buffer capacity of alkaline calcareous soils (Baxter et al, 2023;Dungan et al, 2022). With respect to EC, Bierer et al (2023) found that EC increased due to recent manure applications, but in the present study, we found that after 11 years the EC of the manure treatments was similar to the non-manure treatment. Because the irrigation water (from the Snake River) used in this study is relatively low in salts, any salts added in manure will be leached over time.…”