Responses of sunflower to stand structure and crop population density: effects on leaf area and yield

LÓPEZ PEREIRA, M.; TRÁPANI, N.; PIÑEIRO, G.; HALL, A.J.

Fargo, North Dakota, USA

Congreso; 16th International Sunflower Conference; 2004

Responses of crop leaf area at anthesis and yield to crop population density (CPD) and stand structure were explored. Treatments were variations in CPD (1–14.3 pl m-2 ) combined with variations in inter-plant spacing within the target row and in neighbouring rows. Row spacing was 0.70 cm. In one of the three years, two hybrids of putatively contrasting potential grain number per head were compared, under the assumption that more florets (grains) per head might prove advantageous for maintaining yield in low-density, heterogenous stands. Crops were irrigated and protected from lodging and disease. Land area per plant (AP) was calculated using Thiessen polygons and CPD was derived from AP. Plant and crop leaf area at anthesis, grain yield and harvest index were determined. No advantage accrued, under low-density conditions, to the hybrid with greater potential grain (floret) number. Two other important results were: i) crop yield per unit area increased up to plant population densities well above that of the commercially accepted value; and ii) in two out of three experiments crop yield responses to population density were significantly (P>0.05) greater in crops with inter-row spacings of 1.40 m than in crops of equivalent density grown at 0.70 m between rows. We conclude that the physiological capacity of the plant to set and fill grain does not limit crop tolerance to high CPD, and that these limits must be sought elsewhere (e.g., lodging and/or disease tolerance). In addition, yield responses to inter-row spacing require further study.