NITRIFICATION INHIBITORS: EFFECTS ON NITROGEN LOSS FROM SOILS AND CORN YIELDS

RONALD ALLEN MCCORMICK, Purdue University

Abstract

The nitrification inhibitors nitrapyrin (NP) and etridiazol (ETD) have been shown to decrease N losses (through leaching and denitrification) and increase crop yields when applied to soil with N fertilizers. However, no research has been conducted to determine if adding NP to animal manure subsequently applied to soil decreases losses of applied N. Recent laboratory studies have shown that carbon disulfide (CS(,2)), sodium thrithiocarbonate (STC), and potassium ethyl xanthate (XAN) were effective nitrification inhibitors. A series of laboratory and field studies were conducted to evaluate the effects on yields and N loss from soils of adding NP to liquid swine manure (LSM) used as a fertilizer for corn and to determine the effectiveness of CS(,2), STC, ammonium dithiocarbamate (ADTC), and XAN in reducing fertilizer N losses and increasing corn yields. Nitrification of ammonium in LSM applied to soil was inhibited for 15 weeks and recovery of inorganic N from the LSM band was markedly increased by addition of NP (50 mg/liter). Three years of field trials showed that addition of NP to fall-applied LSM increased corn yields by an average of 46%. Adding NP at 25 mg/liter to spring-applied LSM had no effect on yields, but NP added at 50 mg/liter increased corn yields by an average of 21%. Laboratory incubation studies showed that NP, CS(,2) and XAN were effective nitrification inhibitors. Greatest inhibition from compounds was obtained with (NH(,4))(,2)SO(,4) as an N source and with soils of low pH (e.g., 5.2). However, field studies showed that addition of CS(,2), STC, ADTC, and XAN to spring-applied anhydrous ammonia had no effects on nitrification or recovery of inorganic N from fertilizer bands. Nitrapyrin and ETD delayed nitrification and maintained high inorganic N levels in bands for 7 and 8 weeks, respectively, after application. In 32% of 113 comparisons (3 N sources, 2 N rates, 2 years, and 3 locations) corn yields were increased by adding nitrification inhibitors to spring- and fall-applied N fertilizers. Yield increases from addition of CS(,2), STC, ADTC, and XAN were similar to those obtained from NP.

Degree

Ph.D.

Subject Area

Agronomy

COinS