|Liebman, Matthew -|
Submitted to: ASA-CSSA-SSSA Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: May 13, 2013
Publication Date: N/A
Technical Abstract: Nutrient leaching differs between annual and perennial crops, but nutrient losses from rotations containing both annual and perennial crops are not well documented. This study compared NO3-N and total phosphorus (TP) concentrations in soil water under three crop rotations in Iowa, including two-year (corn-soybean; 2YR), three year (corn-soybean-small grain/red clover; 3YR), and four-year (corn-soybean-small grain/alfalfa-alfalfa; 4YR) systems. Using spring soil-test results, nutrient applications comprised synthetic fertilizers to 2YR corn, and composted manure to supplement legume-residue sources for 3YR and 4YR. Soil water was collected from suction samplers at 1.2 m depth during eight years (2004-2011). The 4YR rotation, during the alfalfa and following corn years, showed smaller NO3-N concentrations and less frequent detection of TP. Mean concentrations of NO3-N were 1.1 mg NO3-N L-1 under alfalfa and 6.5 mg NO3-N L-1 during the following corn crop, compared to average concentrations between 8.7 and 18.1 mg NO3-N L-1 among all other crop-years. Seasonal NO3-N dynamics were distinct among rotations due to differences in mineralization-immobilization of N from decomposing crop residues. Total P results showed the importance of landscape hydrology, as the greatest total P concentrations occurred in one 2YR plot where preferential flow was evident. Among the remaining plots, detection of total P (i.e., >0.02 mg L-1) occurred less frequently (p<0.01) under the 4YR alfalfa and corn crops (0.12) than all crop-years (0.34). Results suggest nutrient management may not always involve a tradeoff between N and P losses, and that crop rotations including alfalfa may reduce losses of both nutrients.