Nutrient Management Research Database

General Information

Research Title

Prediction of leaf nitrogen from early season samples and development of field sampling protocols for nitrogen management in Almond (Prunus dulcis [Mill.] DA Webb)

Link to File

http://link.springer.com/article/10.1007%2Fs11104-014-2062-4

Research Specifications

Crop: Plum

Soil Type: Variable

County, State: (Colusa, Kern, Madera, Stanislaus), California

Year: 2014

Authors

Saa, Sebastian, Brown, Patrick H., Muhammad, Saiful, Olivos-Del Rio, Andres, Sanden, Blake L., Laca, Emilio A.

Summary/Abstract from Original Source

Background and aim

Protocols for leaf sampling in deciduous tree crops are commonly executed too late in the season and do not adequately consider field variability to be effectively used to guide N management. The goal of this study was to develop improved sampling strategies to optimize nitrogen management in deciduous tree crops.

Method

Leaf nutrient concentration from individual trees in four mature commercial orchards was collected (n =1148) for three consecutive seasons to develop nitrogen prediction models and to estimate the distribution of N values in orchards in July. Spatial variance analysis was used to determine optimal sampling strategies.

Results

Leaf nitrogen concentration in summer can be predicted (r² = 0.9) from the leaf N and B concentration in spring with the sum of K, Ca, and Mg equivalents. Mean field leaf nutrient concentration can be obtained by collecting one pooled sample per management zone composed of 30 trees each of which are at least 30 m apart. Using these methods the percentage of trees with leaf N above the recommended July critical value can be predicted accurately.

Conclusions

Optimized methods for sample collection and models to predict mid-season leaf N from early season samples can be used to improve N management in deciduous tree crops.

Research Highlights

Design and Methods

Late season leaf sampling is often too late to allow growers to remedy the issue in-season.
Comprehensive leaf sampling was performed in 4 orchards in April and July in order to develop a protocol that could predict late season N levels with early season sampling.
This study also sought to identify the sampling required to adequately address potential variability between management areas.

Results

Summer leaf N levels could be predicted from spring measurements of N, B, and the sum of K, Ca, and Mg.
Samples pooled from 30 trees spaced at least 100ft apart can be used to estimate N levels for a given management zone.
This protocol allows for the prediction of trees that will have leaf N concentrations above the July critical value.