Water use and root length density of Cuphea spp. influenced by row spacing and sowing date

Cuphea (Cuphea viscosissima Jacq. X C. lanceolata E silenoides W.T. Aiton) is a potential new crop, but little is known concerning best agricultural management practices for this crop in temperate regions. A field study was initiated in Minnesota to determine the impact of sowing date and row spacing on soil water use and rooting characteristics of Cuphea spp. Cuphea spp. were sown on 4, 18, and 30 May 2001 and 30 April, 14 May, and 28 May 2002 in rows 200, 400, and 600 mm apart. Aboveground biomass, seed yield, and water use were bolstered by sowing Cuphea spp. in late April or early May rather than in late May. Water use for early sown and late-sown Cuphea spp. was respectively 366 and 311 mm. Sowing date also influenced water use efficiency (WUE) but only in 2002 when WUE of early sown and late-sown Cuphea spp. was respectively 1.87 and 1.64 kg ha(-1) mm(-1). Sowing earlier in the spring also bolstered root growth as root length density in the upper 0.2 m of the soil profile was 24 km m(-3) for the early sowing and 17 km m(-3) for the late sowing. Row spacing did not affect seed yield, water use, or root length. This study indicates that biomass, seed yield, water use, and root growth of Cuphea spp. are favored by sowing early in the spring. Although early sowing resulted in greater water use, a tendency existed for Cuphea spp. to utilize water more efficiently in seed production when sown earlier in the spring.