Title: Mineral nutrient synergism and dilution responses to nitrogen fertilizer in field grown maize Author
Submitted to: Journal of Plant Nutrition and Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 17, 2010
Publication Date: September 24, 2010
Citation: Riedell, W.E. 2010. Mineral nutrient synergism and dilution responses to nitrogen fertilizer in field grown maize. Journal of Plant Nutrition and Soil Science. 173:869-874. DOI 10.1002/jpln.200900218. Interpretive Summary: Nitrogen fertilizer is an important input for maize productivity. The economic cost of N fertilizer has risen dramatically over the past 6 years. If fertilizer prices continue to rise, application of N fertilizers at current rates could become economically unsustainable. As a result farmers may be under economic pressure to reduce application rates to maize. The experimental objectives were to investigate the impact of different levels of N fertilizer inputs on soil characteristics, on maize shoot growth at different times during crop development, and on maize shoot essential mineral element concentrations. Because N is the most limiting factor for maize growth in many soils, the application of N fertilizer usually results in large increases in shoot dry weight. Unless accompanied by increased mineral absorption rates, N-fertilizer-induced increases in shoot DW may dilute the concentrations of other mineral elements in shoots. In the present study, as shoot DW increased with N fertilizer treatments, shoot concentrations of P and K decreased. Starter P and K fertilizers were applied in a band near the seed furrow. Thus these elements were readily available for root absorption, even in plants given no N fertilizer. A dilution effect for P and K likely took place as shoot DW increased in response to N fertilizer application. Conversely, if fertilizer N increases root growth as well as the volume of soil explored by roots, uptake of soil-immobile nutrient elements may increase. In the present study, N fertilizer application increased shoot DW and also increased shoot concentrations of N, Ca, and Mn. This synergistic response between DW accumulation and N, Ca, and Mn concentrations may have been the result of greater root growth and activity as N fertilizer was increased.
Technical Abstract: Differences in N fertilizer rates could have a major impact on the uptake of N as well as other essential mineral nutrients by maize (Zea mays L.). The effect of N fertilizer (8.5 or 5.3 Mg/ha yield goal, or no N) treatment on soil characteristics [pH, electrical conductivity (EC), organic matter (OM)] and mineral (NO3-N, P, K, S, Ca, Mg, and Mn) concentrations as well as on maize (Zea mays L.) shoot characteristics (dry weight, stem height, and leaf area index) and mineral concentrations at the sixth leaf (V6), twelfth leaf (V12) and tassel (VT) development stages were investigated in a 2-yr study conducted at Brookings SD on a on Barnes loam soil. Decreased soil pH, increased organic matter, decreased NO3-N, and increased S and Mn concentrations were measured within the crop row at the 0-30 cm depth between crop emergence to the VT crop development stage. Soil EC, NO3-N, and S concentration were greater with increasing rates of N fertilizer. As shoot DW increased between V6 and V12 (a twelve-fold increase), individual shoot concentrations of all mineral elements studied dropped between 28 to 48 %. A doubling of DW between V12 and VT was accompanied by a 11 to 19 % reduction in shoot mineral concentrations. With increasing N fertilizer application rates, shoot DW was greater and shoot concentrations of N, Ca, and Mn increased. This synergistic response between DW accumulation and N, Ca, and Mn concentrations may have been the result of greater root growth and activity as N fertilizer was increased. Conversely, as shoot DW increased, shoot concentrations of P and K decreased. Starter P and K fertilizers were applied in a band near the seed furrow. Thus these elements were readily available for root absorption, even in plants given no N fertilizer. Thus a dilution effect for P and K took place as shoot DW increased in response to N fertilizer application.