Articles
The effects of almond hulls and soil amendments on soil nutrients and microbial community within mature almond orchards
Article number
1406_34
Pages
225 – 232
Language
English
Abstract
Almond hulls and shells (H/S) are a major byproduct of almond production.
Due to the nutrient content of H/S, these products could add nutrient and soil health benefits if re-applied to orchards.
In early-May H/S were applied to two almond orchards, one silt loam and the other sand soil, and the effects of these applications were compared to common soil amendments.
For each location there were five treatment groups and one untreated control.
Treatments applied to the soil within the irrigation pattern were: H/S at 2.2 t ha-1, calcium sulfate (gypsum) at 560 kg ha-1, and a 50:50 biochar:compost mix at 1.125 t ha-1. Treatments of 6% humic acid product at 28 and 47 L ha-1 per application were delivered through the micro-irrigation system three times at an interval of 2 weeks.
Soil chemical, physical, and microbial properties were evaluated multiple times during the production season.
Leaf nutrient levels were sampled at week 10 post treatment (PT). Soil chemical properties were evaluated at week 4 and 8 PT. Microbial activity was monitored at week 2, 4, and 6 PT using hydrolysis of fluorescein diacetate (FDA), beta-glucosidase (BG), and acid phosphatase enzyme assays.
No treatment impacted leaf nutrient levels, volumetric water, soil water holding capacity, water infiltration, or bulk density.
At both trial locations treated with gypsum there was an increase in total salts and exchangeable calcium levels.
There was an increase in exchangeable potassium at the sand soil site treated with H/S. In both the gypsum and H/S-treated silt loam site, there was an increase in aggregate stability.
At both locations treated with H/S, there was an increase in FDA, indicating increased microbial activity.
Differences in BG levels were found among some treatments but were not consistent across trial locations.
H/S decomposed by mid-July and did not interfere with harvest operations.
H/S applications provide some soil health benefits, and can be re-applied re-introduced into an almond orchard without impacting orchard operations.
Due to the nutrient content of H/S, these products could add nutrient and soil health benefits if re-applied to orchards.
In early-May H/S were applied to two almond orchards, one silt loam and the other sand soil, and the effects of these applications were compared to common soil amendments.
For each location there were five treatment groups and one untreated control.
Treatments applied to the soil within the irrigation pattern were: H/S at 2.2 t ha-1, calcium sulfate (gypsum) at 560 kg ha-1, and a 50:50 biochar:compost mix at 1.125 t ha-1. Treatments of 6% humic acid product at 28 and 47 L ha-1 per application were delivered through the micro-irrigation system three times at an interval of 2 weeks.
Soil chemical, physical, and microbial properties were evaluated multiple times during the production season.
Leaf nutrient levels were sampled at week 10 post treatment (PT). Soil chemical properties were evaluated at week 4 and 8 PT. Microbial activity was monitored at week 2, 4, and 6 PT using hydrolysis of fluorescein diacetate (FDA), beta-glucosidase (BG), and acid phosphatase enzyme assays.
No treatment impacted leaf nutrient levels, volumetric water, soil water holding capacity, water infiltration, or bulk density.
At both trial locations treated with gypsum there was an increase in total salts and exchangeable calcium levels.
There was an increase in exchangeable potassium at the sand soil site treated with H/S. In both the gypsum and H/S-treated silt loam site, there was an increase in aggregate stability.
At both locations treated with H/S, there was an increase in FDA, indicating increased microbial activity.
Differences in BG levels were found among some treatments but were not consistent across trial locations.
H/S decomposed by mid-July and did not interfere with harvest operations.
H/S applications provide some soil health benefits, and can be re-applied re-introduced into an almond orchard without impacting orchard operations.
Authors
D.A. Doll, V.D. Lopez, A. Gaudin
Keywords
soil health, agricultural byproducts, agricultural circular economy, orchard health
Groups involved
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