Nitrification Inhibitor Influences on Potato

Abstract

Nitrification inhibitors may reduce loss of fertilizer N from the root zone by reducing leaching and denitrification. This reduced N loss should be reflected in increased crop yields. These studies were con· ducted to determine if potato yield, specific gravity, or leaf N at flow· ering would be increased by use of nitrification inhibitors. Nitrification inhibitors dicyandiamide (DCD) and 2-chloro-6-(trichloromethyl)· pyridine (nitrapyrin) were evaluated in five studies on potato (So· Ianum tuberosum L. cv. Atlantic) in Northeast Florida on an Arenic Ochraqualf, a Grossarenic Paleudult, and a Grossarenic Paleaquult. Treatments were combinations ofN at 67, 134, and 202 kg ha-•; DCD at 0, 5.6, and 11.2 kg ha-•; nitrapyrin at 0.56 and 1.12 kg ha-•; and isobutylidene diurea (IBDU) applied as one-third of the N. Tuber yields were not affected by nitrification inhibitors in four of five tests but were increased 14% in one test. Nitrification inhibitors increased leaf N concentration at flowering in three of four tests. Tuber yields were higher with DCD than with nitrapyrin in three of five tests. In several year-location combinations, use of IBDU resulted in greater tuber yield and leaf N concentration at flowering than did nitrification inhibitors. Based on these results, nitrification inhibitors can not be recommended for potato production on hyperthermic, sandy, irri· gated soils.

Potato Response to Nitrogen Form and Nitrification Inhibitors

“…This is somewhat similar to the data of Martin et al (1993), where they only observed an inhibitor effect on specific gravity in 1 of 5 site-years; however, in the significant year, they saw a decrease in specific gravity as inhibitor rate increased. As with the Martin et al (1993) data, our data do not follow the suggestion of Westermann and Kleinkopf (1985) that treatments which increase yields tend to decrease specific gravity as 1984 was the only year we saw a positive yield increase from inhibitor use.…”

“…The use of DCD did not affect total yield in 1986. These sporadic benefits to inhibitor use on potato yield are similar to the results of Roberts (1979) where response was seen in 2 of 3 years and Martin et al (1993) where they only saw a benefit in 1 of 5 site years.…”

“…Tuber yield and quality reductions were also seen in a 2-year Texas study where N sources included ammonium sulfate, urea, or sulfur-coated urea (Vendrell et al 1981). These results are in contrast to other studies that showed either no change in crop yield or quality (Potter et al 1971;Penny et al 1984;Sahota and Singh 1984;Vos 1994), or in some cases, yield increases or increases in apparent recovery of the fertilizer N applied by the tubers (Roberts 1979;Sahota and Singh 1984;Wadman et al 1989;Bailey et al 1992;Martin et al 1993).…”

“…In the previous studies where yield and/or quality reductions were observed, the inhibitors were added to all ammonium or ammonium-forming N sources, whereas the Roberts (1979) and Martin et al (1993) studies used mixed NH 4 + and NO 3 -sources. Dicyandiamide was added to liquid manure for the Wadman et al (1989) work.…”

Nitrification and denitrification in subalpine coniferous forests of different restoration stages in western Sichuan, China

“…Due to ignorance of the NO 3 −1 assimilation in soil microbial communities, the net nitrification rates were greatly underestimated (Stark and Hart, 1997). Reports on nitrification and denitrification are rich in the agricultural ecosystem (Martin et al, 1993;Rochester et al, 1996;Shi and Norton, 2000;Schjønning et al, 2003), however, scarce in the forest ecosystem, especially on the dynamic process along restoration or succession of forest ecosystem (Davidson et al, 1992;Zou et al, 1992;Carmosini et al, 2002). Furthermore, there are obviously different results on the dynamic properties of nitrification along forest succession: Rice and Pancholy (1972) reported that nitrification decreased in the course of succession, Davidson et al (1992) showed that the gross nitrification rates were not different between the young and old stages of forest succession, and Zou et al (1992) concluded that the old-growth forest tended to have higher gross nitrification rates than the early-successional one after studying the forest soils in the Caribbean lowland in northeastern Costa Rica.…”