Crop N Guidelines: Sod N

Another major N credit to include in the corn N requirement is the N released when sods are tilled under and/or killed.

Sods of all kinds (e.g. alfalfa, grass, mixes, etc.), when tilled under or killed, will release large amounts of plant available N for up to 3 years after the plowing (see the table, below). The N in the sod residue is mineralized over time by soil microorganisms, thereby making the N available for the next crop in the rotation, for example corn. The table, below, contains average annual N availabilities from four major categories of plowed/killed sods. The amount of N released depends on the percentage of legume in the plowed sod, as well as all of the factors that drive N mineralization and nitrification. The percent legume in the sod is based on your in-field estimate of the proportion of legume plants to non-legumes (i.e. grasses, etc.) in the stand.

How many lbs of N/acre are available to a first year corn field following a sod of 26-50% legume?

Legume in Sod	Total N Pool	Year 1*	Year 2	Year 3
%	lbs N/acre	lbs N/acre	lbs N/acre	lbs N/acre
0	150	83	18	8
1-25	200	110	24	10
26-50	250	138	30	13
50 or more	300	165	36	15

*First year following tilling under and/or killing sod.

To read more on this subject: Nitrogen Guidelines for Field Crops in New York (section 3.2).

To download an Excel spreadsheet for calculating the N contribution from sods: Sod N Calculator.