Direct Seed Sowing Techniques for Agroforestry and Reforestration

Commodities

Practices

Tree planting is increasingly important as silvopasture, agroforestry systems and habitat restoration projects expand. The cost and limited availability of seedlings is one limitation to such projects as the nursery industry is slow to expand. Tree seeds, however, are cheaper and more readily available than bare root trees. Methods for direct sowing seeds exist for tilled ground in nursery settings, but not for direct sowing in situ. Forestry tree planters are well designed for planting bare root trees in situ but are missing small but key design features that would make them optimal for sowing tree seeds.

After using using a tree seedling planter to test direct sowing roughly 14,000 bur oak acorns in situ at the MCRA we have identified two problems that our proposed modifications would address 1) it was difficult to place tree seeds in the furrow accurately and at consistent spacing, and 2) the wheels that press the furrow closed only function when the planter is set to a depth of roughly 6’’ or greater, which is not an ideal depth for planting seeds.

Our solution is to modify an existing tree planter to direct sow tree seeds in situ at varying depths and spacing. The specific modifications  1) an on-board hopper that can effectively drop seeds in the furrow, and 2) adjustable height on packing wheels to allow the furrow to effectively close even at shallow planting depth.

[caption id="attachment_1196738" align="alignnone" width="300"] Drawing of standard forestry tree planter.[/caption] [caption id="attachment_1196739" align="alignnone" width="300"] Drawing of modified tree planter for agroforestry.[/caption]

Fabrication, testing and refining of the planter attachments/modifications will occur in spring and early summer 2025.

Once a prototype is finished, the equipment will be used to plant 6 500 foot rows with either tree seed or bare root seedlings. The planting will incorporate 3 species representing different seed size groups (large: pecan, medium: persimmon, small: elderberry), so that side by side comparisons can be made between the cost and efficiency of bare root planting vs direct sowing.

Row 1: Bare root pecans seedlings

Row 2: Direct sow pecans

Row 3: Bare root persimmons

Row 4: Direct sow persimmon seeds

Row 5: Bare root elderberry seedlings

Row 6: Direct sow elderberry seed

These rows will be planted in the fall of 2025. Planting will be described in writing and the process will be recorded on video and shared publicly. At 6 and 12 months, the planting will be surveyed to determine the number of living stems in each row, and the average calliper of stems. In late 2026, these data will be used to determine the effective cost per living tree for direct seeding compared with bare root planting. At 12 months, a sample of trees from all 6 rows will be dug up to compare root structure between transplanted bare root stock vs seeds that germinated in situ. The results will be shared via a publicly available white paper and video and photo content on social media channels associated with Powell Gardens and the MCRA.

 

There are 4 objectives 

1. Develop a modular, easy to build hopper that can sow a variety of tree seeds into the furrow on a forestry tree seedling planter,
2.  Demonstrate the difference in cost and performance (calliper and root structure) between direct sown and bare root planted trees
3. Publicize design and all results via social media and on farm demonstrations.
4. Encourage other practitioners to more effectively and cheaply plant more trees for agroforestry, silvopasture and reforestation.