Potato nitrogen management by monitoring petiole nitrate level

Petiole nitrate nitrogen (NO3‐N) concentrations have been successfully used in Northwestern New Mexico to make timely nitrogen (N) recommendations for irrigated potatoes. However, a quick test and consistent sampling time is needed to precisely determine fertigation and to prevent over fertilization, especially in sandy soils. This study examined the petiole NO3‐N dynamics during the growing season for both chipping and table stock varieties. Readings from a quick in‐field sap NO3‐N meter were highly correlated with NO3‐N indications using the conventional laboratory method. The sap NO3‐N meter can significantly reduce testing turnaround time and has great potential for potato N management. Results showed that most consistent NO3‐N readings could be obtained by collecting tissue samples between 1100 and 1400 hours of the day.