Crop rotation impacts on potato protein.

The impact of nitrogen (N) fertilization on potato (Solanum tuberosum L.) protein yield and nutritional quality is well documented but of little benefit to growers with limited access to fertilizer or capital (e.g. in lesser developed countries). This study was conducted 1) to evaluate the extent which crude protein yield in potatoes can be influenced by crop rotation with no N fertilizer and 2) to determine if crop rotation and minimal application of N fertilizer can meet the total protein yield of potatoes achieved with recommended quantities of N fertilizer. A field study was conducted in which potatoes followed previous crops of alfalfa (Medicago sativa L. 'Nitro'), hairy vetch (Vicia villosa Roth), white lupin (Lupinus albus L. 'Ultra'), oats (Avena sativa 'Astro'), and potatoes. Tuber protein yield following alfalfa with no N fertilizer was about 50 kg/ha greater than when following potatoes or oats in one study year. In another year, tuber protein yield was greatest following vetch, achieving 149 kg protein/ha with no N fertilizer. These results were directly linked to the N contributions of rotation crop residues and were reflected in the plant-available N levels measured in soil. Applying one-half the recommended rate of N fertilizer resulted in protein yields comparable to a well-fertilized potato-potato rotation in a relatively dry year, but not in a year with more favorable precipitation. Particular crops grown in rotation with potatoes can make significant contributions to the total protein harvested in tubers.