As a potato grower, the number, size, shape, and color of the tubers you dig at harvest affect your income. These four characteristics are influenced by how deep seed tubers or pieces were placed at planting and the width and height of the hill created and maintained from planting to crop maturity. This article provides examples of how seed depth and hill size and shape affect tuber yield and quality. Given these examples and other information, growers may wish to evaluate their variety-specific seed placement and hilling operations, particularly because stolon or tuber initiation is underway in many area potato plantings.
1. The plant genetics factor. Tubers form at the tips of stolons which arise from the stem(s) developing from the seed piece or tuber. Most stolons extend from points on stems above the seed piece/tuber, although stolon tips may reach below it. Similarly, the number of stolons most likely to develop on a plant and, therefore, its tuber yield potential, tends to differ among varieties. Once initiated, stolon length can vary with growing conditions, leading hills to hold few to many generally tightly or loosely bunched tubers. Carefully hand-digging young plants to examine their stolons and newly initiated tubers and completing test digs at various stages of tuber development is very informative. The combination of stolon number and length and growing conditions shapes tuber characteristics. Optimal planting depths and hill conditions maximize tuber yield and quality. Proper hilling increases the volume of soil available for light-free tuber development and can assist with weed control.
2. The soils factor. Regardless of seed depth, stems and young plants must develop before stolons and tubers can, so promoting rapid, high, and uniform emergence is key. Warm, loose/friable soil with the optimal level of moisture promotes grower-friendly stand establishment, a foundation for large, high-quality crops. Of course, what is required to maintain those soil conditions planting through stand establishment and tuber initiation and development differs by soil type (especially texture), at minimum. Indeed, research and experience have shown that optimizing seeding depths and hilling operations requires adjusting them for coarse-to-fine textured soils and varieties used in specific fresh and processing markets. Reviewing reliable resources and completing on-farm tests will help determine the seeding depths and timing, intensity (e.g., amount of foliage buried), and number of hilling operations that are optimal for your operation, given the major soil-variety/market combinations you work with.
3. The market factor. Individual fresh (tablestock) and processing (e.g., potato chip) markets require tubers with many specific characteristics. Tuber number, color (greening), shape, size distribution, and specific gravity are among the market traits that can be influenced by seed depth and hilling operations — i.e., seed depth and hilling as they interact with and are influenced by soil and other conditions. Taken together, plant genetic, soil, and market factors explain why planting depths and hilling regimes should be tailored to the operation and adjusted within and across seasons as varieties, as soils and markets require. Currently, potato seed in Ohio and the region is often placed 4-8 inches deep in single-row hills which are reshaped once or twice after emergence while vines remain mostly upright. Approximately 20-30 percent of the visible foliage or rosette is buried at each hilling. Burying a large percentage of foliage at any time or hilling after vines “flop” and begin to close rows can be damaging. Similarly, hilling under conditions that may promote compaction or interfere with further vine or tuber development is also counterproductive.
