How Rocks Affect Growing Potatoes

Inadequate Root Formation

• Potato plants are heavy feeding crops, requiring large amounts of nitrogen and potassium in addition to water to develop tubers of good quality. A strong, healthy root system is vital to a potato plant's adequate uptake of water and nutrition. The root system is wider than it is deep, growing at a depth of roughly 12 inches. Rocks in garden soil negatively affect growing potato plants because their root systems may not enough have room to grow or may become stunted due to rocks in their way. If a potato plant root systems are stunted or malformed, the plants may not receive enough water or nutrients to develop healthy tubers.

Misshapen Tubers and Diseases

• Rocks in garden soil also get in the way of tubers' development. If rocks are left in the way of developing tubers beneath the soil surface, the result is tubers that are misshapen or damaged. Rocks are not the only culprits, however; heavy clay soil also impedes healthy tuber development. Clay and rocky soils also lack drainage abilities; good drainage is an essential requirement for growing potatoes. Without proper drainage, soil becomes overly wet, leading to problems with bacterial and fungal diseases. Common diseases of potatoes due to improper drainage include pink water rot and bacterial soft rot.

Bruising Problems

• When potato tubers grow in or are harvested from rocky soil, bruising typically occurs. Three kinds of bruising occur from potatoes contacting rocks in soil. The first is called blackspot bruising, in which a rock damages the flesh under a potato's skin. This type of bruising results in dark spots that are visible on the potato's flesh when the potato is peeled. Skinning, another type of bruising, occurs when a rock rubs off the skin of a developing tuber. The skinless area turns dark as a result. Shatter bruising happens when a rock pierces or cracks the skin and flesh of a potato. That kind of bruising is particularly bad for a developing tuber and raises the chance of the potato crop being lost to bacterial soft rot, Fusarium dry rot or early blight diseases.

Solutions

• Providing potato plants with loose, fertile, well-draining soil ensures they develop and produce the healthiest tubers possible. A sand, silt or loam mixture of soil is preferable. Amending heavy clay soil with compost is a way to improve its drainage.

  Prepare the soil prior to planting by tilling it and removing rocks from it. Overtilling soil, however, leads to oxygen loss, crusting and a break down in the soil's overall structure. Plant your potato seeds at a depth of 3 inches in rows that are 2 to 3 feet apart to account for the size and development of each potato plant's root system. If soil is too rocky or too poorly draining, consider planting potatoes in raised beds that are about 15 inches deep.