Sampling & Analysis
A five-year fertigation trial of nitrogen and potassium treatments is underway in almond orchard in Kern Co. The trial consists in 12 fertilization treatments under Micro-sprinklers (Fan Jet) and Drip irrigation. Each of the 12 treatments (Table 1) is replicated in five or six blocks with 15 trees per block.
SOP was applied in two feet wide strips in winter whereas UAN 32, CAN 17, KCl and KTS were split in four fertigation cycles in February, April, June and October as 20, 30, 30 and 20% of total.
Table 1. Fertilization Treatments. |
Data Collection
- Leaf samples were taken 4 times during the season.
- Nut samples were taken 5 time during the season.
- Samples analyzed for N, P, K, B, Zn, Ca, Mn, Mg, Fe, S, Cu
- A total of 768 individual trees monitored for nutrients & yield
- Trees from different N rates were excavated to determine biomass and nutrient storage capacity
Main Results
- *file140412*Nitrogen exported by 1000lb kernel yield was 55lbs and 70lbs for N rate 125lb/ac and 350lb/ac.
- At harvest total 152lbs and 268lbs N were removed by N rate 125lb/ac and 350lb/ac respectively; however there was no significant difference in total N removal at harvest between N rate 275lb/ac and 350lb/ac (data not shown).
- 1000 lbs kernel yield exported 9lbs and 7.8lbs P from the orchard for N rate 125lb/ac and 350lb/ac respectively (Fig 1).
- K export in fruit for 1000lb kernel yield was recorded 74lb and 82lb K for K rate 100lb/ac and 300lb/ac respectively.
- 80% of N, 70% of P and K accumulates in the fruit before 126 DAFB (mid June in 2010).
Significant effect of nitrogen rate on tissue nutrient concentration, yield and fruit nitrogen export has been observed. | Table 2. Mean kernel yield for N rate & source treatment in 2011; treatments with different letter within irrigation are significantly different. |
| Despite significant leaf K concentration no significant differences in yield have been observed for K rate treatment. Fruit potassium accumulation increased over time but was not significantly influenced by K treatment suggesting that K availability at this site was not rate limiting (Fig. 2). The two highest N treatments produced similar kernel yield under both drip and fan jet irrigations whereas the kernel yield significantly decreased as the N rate did.The nitrogen use efficiency (NUE) obtained from N 275lb/ac N rate was 81%, the highest value ever recorded in agriculture setting, there was no benefit from N application in excess of this value. For more information see the presentations and publications under Outreach Fig. 2. Potassium accumulation by 1000lbs kernel yield from K rate treatment in 2010. Each point represents mean and std error. | Fig. 1. Nutrient accumulation by 1000lbs kernel yield from N rate treatments in 2010. Each point represents mean and std error. Tree excavation to determine tree biomass and nutrient storage in perennial parts |