Evaluation of Bamboo as a Silica-rich Mulch for Apple Trees

Commodities

Practices

We propose the use of locally sourced bamboo as a sustainable mulch for apple trees.  In our area there are several stands of bamboo that were planted decades ago which can serve as a renewable source of mulch material.

Bamboo mulch has numerous advantages over hay.  First, it degrades much more slowly and, therefore, will require fewer applications which translates to reduced labor and associated costs.  Bamboo mulch also does not contain viable weed/grass seeds that can sprout, so it will require fewer applications of breakthrough weed control.  Again, this translates to reduced labor, as well as herbicide input costs. It also has low nitrogen drawdown and leads to noticeably increased worm activity. 

Perhaps the most compelling reason for trying bamboo mulch is related to the fact that bamboo is rich in the trace mineral silica, which may improve the health of our apple trees. Silica plays a crucial role in plant growth and health and is beneficial for the leaves to withstand microbial invasion and insect infestation.  It has been shown in university and field studies to improve cell wall strength, root mass and density, and above ground structural integrity, which should result in trees that will be better able to withstand wind and storms that might damage foliage, branches, and fruit.  Silica can also improve plant resistance to both abiotic and biotic stress.  Abiotic stressors such as drought, excessive heat, and freeze events have been increasing as we experience climate changes. By boosting the natural pest and disease fighting systems of the plant, supplemental silica should help reduce pest infestations and pathogenic bacterial and fungal colonization.  In addition, leaves of plants with silica exposure have been shown to contain higher amounts of chlorophyll.  And as a micronutrient, silica positively impacts the uptake of other nutrients such as boron and calcium, therefore we will be looking at those co-migrators in the sap and soil analyses.  There is a commercially available foliar product called SilMATRIX that is marketed as a silica supplement for fruit trees, but it is prohibitively expensive for our orchard, and we hope to take advantage of the local abundance of renewable bamboo.

After treating the fruit tree rows with vinegar to burn down grass and weeds, we will apply an approximately 6-inch layer of bamboo mulch.  Many studies that have shown benefits of silicon amendment have been in low pH environments.  The intermittent application of vinegar to control breakthrough weeds may be beneficial in this aspect.

In our orchard, apple varieties are planted in blocks comprised of 3 rows.  We intend to test our hypothesis in the 36-tree Father Abraham block of our orchard.  The northern row of Father Abraham trees will be managed with hay mulch, the middle row of trees will not have any mulch, and the southern row of trees will be managed with bamboo mulch.  In addition, all three rows will be sprayed with 30% vinegar to burn down grass/weeds.  Vinegar treatments will be performed at the start of the project (prior to application of mulch) and approximately 4-6 times during the growing season, as needed.

In order to determine the impact of bamboo mulch/vinegar on the soil and tree health, quantitative assessment in the form of soil tests, sap analysis, and leaf analysis will be performed at several timepoints. 

New Age Laboratories will provide reports which will include macronutrients, micronutrients, pH, nitrogen parameters, nutrient balance, trace elements, metabolic sugars, Brix, electrical conductivity (EC), etc.  Since leaf samples sent for analysis include both new and old leaves for comparison, it will be easy to determine changes at each timepoint.  Although overall results will be tracked, particular attention will be paid to the amount of silicate mineral detected in ppm (hopefully attributed to the bamboo mulch) and the pH (to ensure that repeated vinegar applications do not alter this parameter to a deleterious degree).

Qualitative assessment will also be performed by observation of pest burden and disease incidence on the tree as well as on the fruit.  Since silica is expected to improve the integrity of the leaves, we expect to see reduced fungal disease in the trees that are mulched with bamboo.  We will also record observations on fruit size, premature fruit drop, and overall yield.