Effects of soil tillage and fertility management on acid phosphatase activity in corn ( <i>Zea mays</i> L.) in two long‐term crop rotations

Abstract Enzyme activity studies provide an indicator of soil health related to soil management practices. As land area seeded to corn ( Zea mays L.) and corn yields increase in this region, demands for plant nutrients also increase to support the high yields. Phosphorus (P) is the second highest fertilizer input in corn production representing a significant input cost. Phosphatase enzymes are produced by soil microorganisms and plants and aid in the release plant available P from soil organic matter when fertilizer P is limited. This is among the first acid phosphatase (ACP) activity studies of long‐term (36 years) corn rotations with contrasting fertility regimes in the Northern Great Plains. Relationships between ACP and tillage type, nitrogen rate, and manure application under limited P fertilizer applications was evaluated in two long‐term (36 years) corn rotations in east‐central North Dakota. Acid phosphatase activity was determined on soil samples from the corn root zone from two crop rotations representing common crop mixes grown locally. Phosphatase measurement in contrasting tillage (clean‐till vs. no‐till), nitrogen (N) rates (0 and 168 kg ha −1 ), and manure (with or without) applications showed that tillage and N rate did not significantly affect enzymatic activity. Manure applications significantly reduced ACP activity by 38%–50% indicating P accumulation suppressing enzyme activity, suggesting trade‐offs of practices with soil health. Phosphatase activity was negatively affected by soil pH and soil test P ( p ≤ 0.001) but not affected by soil organic matter and appeared to be within levels found in the literature due to maintenance of soil test P at medium levels.