Effects of Plant Density On Yield and Tuber Quality in Red Norland Potatoes.

Plant spacing of potatoes is based on past equipment capabilities and cultural practices.  The standard plant spacing is 91 cm row spacing between rows with 23 cm in-row plant spacing which may result in a longer period for canopy closure.  Delayed canopy closure may result in under utilization of sunlight for photosynthesis and allow for more rapid weed growth. Red potato yield and quality could be improved by narrowing the plant spacing and increasing plant density. The objectives of this study are to determine the effect of plant and row spacing on red potato yield and quality and compare weed populations and density among different plant and row spacing. The study consisted of a randomized complete block design, with three replications of five treatments.  Planting pattern treatments were equidistant at 23, 30.5, 38, and 45.5 cm except for the control which used standard practices. The plots were planted and harvested by hand in 15X10 ft beds. In 2008 and 2009, potato tuber yield increased with decreasing plant spacing with 26 and 65 Mg ha^-1for the control to 51 and 75 Mg ha^-1 for the 23 cm equidistant spacing.  The number of tubers also increased with decreasing plant spacing with 4 x 10⁵ tubers (both years) for the control and 8.8 x 10⁵ (2008) and 12 x 10⁵ (2009) tubers for the 23 cm spacing.  Comparison of mean tuber size among treatments showed that only the 23 cm spacing had smaller tuber size (51 g).  Quicker canopy closer results in less weed pressure, reduces use of herbicides, and is more efficient in utilization of sunlight and nutrients. The result of higher density planting is a smaller tuber size which can be more desirable in red potatoes. At a closer spacing, plant numbers increase per hectare, thus yield and potato quality for reds increase. The advantage of higher density planting is the increased number of marketable tubers, less field compaction, and lower production costs.