Effects of Plant Density on Growth and Biomass Partitioning in Pickling Cucumbers

Abstract

Abstract Pickling cucumbers (Cucumis sativus L. cvs. Tamor and Castlepik) were direct-seeded at six plant densities (in thousands, 44, 77, 97, 121, 152, 194) using two between-row spacings (71 and 36 cm) and three within-row spacings (29, 14, and 11 cm between plants). Compared with the 29 cm within-row spacing, the 11- and 14-cm spacings resulted in significantly lower total above-ground plant dry weights, growth rates, and total leaf areas for both cultivars as early as 21 to 27 days after planting. The between-row spacing effects on plant growth were similar, but were of a lower magnitude and appeared later in plant development than for the within-row spacing effects. Leaf lamina and fruit tissue exhibited the largest reduction in tissue dry weights per plant compared to stem and petiole tissue when plant density was increased from ≈4.5 to 20 plants/m−2 (45,000 to 200,000 plants/ha). Lower fruit productivity per plant at higher plant densities resulted from fewer fruit set per plant and lower fruit : shoot ratios. Unit leaf rate (g dry weight/day per g of lamina dry weight) was not affected by plant spacing during the fruit development period. Increased densities resulted in significantly higher leaf area indexes, and vegetative and total above-ground dry weights/m−2. Total fruit yield with a single harvest did not increase above ≈77,000 plants/ha for both cultivars. A high correlation (r = 0.877) between leaf lamina dry weight and fruit growth rate indicates that net photosynthetic capacity might be limiting fruit productive potential in pickling cucumbers.