|How to Maximize NUE|
Rotation: Because rotations in dryland production are dependent upon moisture
availability, no specific rotation for improved NUE can be recommended. However, we
believe that the development of an easily mineralizable organic N fertilizer
supply) would be consistent with the continued but low demand for N over the season in
dryland production and/or slow release N that would come from an incorporated legume.
Production system: Forage production systems when compared to grain are much more efficient in their use of N, since harvest takes place prior to flowering after which gaseous plant N losses become significant. Plant N loss helps to explain why grain production systems are less N efficient.
Plant Breeding: Simultaneous selection for improved WUE and NUE, varieties with high HI, low forage yield and low plant N loss
Tillage: N fertilizer use efficiency is known to be lower in zero-tillage when N is applied to the surface. Decreased NUE for zero or reduced-tillage compared to conventional tillage can be expected. Although conventional tillage is recommended at this time for increased NUE, it should not be condoned at the expense of increased soil erosion. Surface application of N fertilizer in zero-tillage systems should be avoided.
N Source: Provide NH4 supply under low N inputs and NH4+NO3 under high N inputs. Inhibit nitrification under low N input (low yield potential) and stimulate nitrification under high yield potential
Preplant and in-season applied N: Applied N as NH3 split for forage production. For grain production, no N applied preplant, with NH3 applied once in-season, or UAN knifed in late February.
Spring applied foliar N: Rates of foliar applied N, post flowering in wheat should be within 10 and 25 kg N ha-1 and should effectively increase NUE when combined with preplant N rates less than the average required for estimated yield goals.
Precision Agriculture and Application Resolution: Sense and treat each 1m2 independently using NDVI at early vegetative stages of growth. N rates used for the first application will not be selected to obtain maximum yields, but rather a first approximation to adjust for the variability present (0- 50 lbs). The second application will apply a similar range of N, but at a time when yield potential can be better defined.
1. Increased supply of NH4 under low N inputs, NH4+NO3 under high N inputs "A" Retain N fertilizer within ORGANIC Matter, NH4, Microbial/Plant N sink or slow-release NH4
Nitrogen Pathways that are Inefficient
B1 Harvest of forage prior to anthesis when plant N loss takes place B2 Increased aeration for decreased denitrification