Assessment of Nutrient Status in Almond
For the variability assessment trials, leaf samples are taken five times during the season from within the canopy of each of 1054 replicate trees from 4 locations (Arbuckle, Salida, Madera, Belridge). Leaf samples are taken from:
- Non-fruiting spurs (NF): short branches that do not produce fruit
- Spurs with one fruiting spur (F1): short branches producing one fruit
- Multiple fruits (F2): branches producing multiple fruits
Samples are analyzed for N, P, K, B, Zn, Ca, Mn, Mg, Fe, S, and Cu at UC Davis DANR lab. Nut samples are also taken and individual tree yields are recorded for the season. The data on nutrient content of nuts and their biomass at each sample date stage is related to final tree yield and nut weight to develop a curve of seasonal nutrient and biomass accumulation. individual tree harvest will be performed three days prior to commercial field harvest by selectively shaking individual experimental trees then raking and weighing by hand
We will use a combination of linear and non-linear statistical approaches utilizing both individual tree analysis and blocked treatments, replicated over several years. Analysis will include:
Preliminary Results For First Two Seasons (2008-09)
Preliminary analysis indicates that early nutrient deficit seems to be consistent during the season and spatially correlated with yield. Data also suggests that is a window for implementing early season nutrient prognosis (Fig. 1).
There is an important variability between sites for some nutrients such as P, K, S, and Cu. However, a more consistent pattern between sites is observed for nutrients such as N, Zn, and Ca (Fig. 2).
There is a significant local deficit between NF/F1/F2. Multiple fruit spurs have a significantly lower nutrient concentration than non-fruiting spurs during the whole season (Fig. 3).
Results presented here represent only 18 months of a long-term experiment and must be interpreted with caution. However, some tentative observations include:
- Substantial variability has been observed in nutrient concentrations within field, between fields and within trees.
- Nutrient-deficient leaves on fruiting spurs, but not on non-fruiting spurs of the same tree, suggest that current management protocols may not be adequate.
- Predictable change rates in nutrient concentrations suggest that early season leaf analysis may be useful for nutrient management.
- Nutrient export from leaves in harvested crop suggests a potential for high nutrient use efficiency in almond, which declines rapidly as N application increases beyond optimum.