Interception and Radiation Use Efficiencies previous to seed filling in quinoa

H D BERTERO; R A RUIZ; S SIFFREDI

Copenhague, Dinamarca

Congreso; VIII ESA (European Society of Agronomy) Meeting; 2004

European Society of Agronomy

Introduction Sea level quinoa (Chenopodium quinoa W.) cultivars (originating from Chile or selected from lines of that origin) can be cultivated in temperate environments (Mujica et al., 2001).  Basic aspects of crop dry matter production and yield determination are ignored  for this species, however. Here we report fraction of radiation intercepted (F), its determinants leaf area index (LAI)  and light extinction coefficient (k)), and Radiation Use Efficiency (RUE, g dry matter MJ-1) estimates for a winter sowing in the Argentinean pampas. Material and Methods: Four cultivars: NL-6 (Holland), RU-5 (UK), CO-407 (USA) and Faro (Chile), were cultivated at two densities: 22 (D1) and 33 (D2)  pl m-2   in a factorial experiment with four replicates. Crops were sown on August 28,  2003 at  INTA (National Institute for Agricultural Technology) Pergamino (33¡ã 34¡¯ S, 60¡ã 35¡¯ W) Argentina, and received supplementary irrigation  and fertilization (20 kg P and 218 kg N ha-1). Insect pests and fungal diseases were prevented and weeds removed by hand.  Starting 1 month after emergence,  5 plants per replicate were sampled weekly for LAI (m2 leaf m-2 soil) and above ground  dry matter (g m2) estimation.  Total incident radiation (MJ m-2 d-1) values were estimated from relative sunshine (Magr¨ªn et al., 1993). F (1-transmitted radiation/incident radiation) was measured at each sampling date  using a Decagon ceptometer.  The association between F and LAI was characterized as: F = (1- exp (-k. LAI)) x 100 RUE values were estimated by fitting a linear regression (forced through zero) to the accumulated dry matter vs accumulated intercepted radiation from emergence to the end of flowering relationship. Average maximum and minimum temperatures during crop cycle were 27,1 and 11, 8 ¡ãC respectively,  and average total incident radiation 21,7 MJ m-2 d-1. Results and Discussion Crops emerged on September 4 and differed in duration of development. NL 6 was the earliest to flower (1st opened flower) and mature (49 and 103 days, respectively) followed by RU-5 (63 and 109d), CO-407 (69 and 116d) and Faro (76 and 124 d). Cultivar differences in days to maturity were positively associated to duration of the vegetative (emergence to visible floral buds) and reproductive (visible floral buds to 1st open flower) phases. Expansion of leaf area ceased at the end of flowering, and cv. differences in maximum LAI and F values followed the ranking in development. Higher densities resulted in significant increases in maximum LAI and F values. A single relationship adequately described the association between F and LAI, with a k value of 0,534 (Fig. 1a) . Critical leaf area value (C LAI, LAI at 95 % F) reaches 5.6 m2 m-2, what  places quinoa close to cereals (Flenet et al., 1996). RUE (averaged across cvs. and densities) was 1,145 g  MJ-1, within the range for C3 crops (Sinclair and Muchow, 1999) (Fig. 1 b).                   Fig 1. Association between F and LAI (a) and between accumulated aboveground dry matter and intercepted radiation (b) from emergence to the end of flowering. Symbols: ¡ñ (C0 407), ¨ˆ (Faro), ¡ø (NL-6) and ¡ô (RU-5). D1 (open symbols), D2 (closed symbols).  As observed in the figures, differences in maturity resulted in important differences in dry matter production. An increase in emergence to end of flowering duration of 27 days (the difference between the earliest and the latest cv.) can be translated into a more than two fold increase in radiation interception (from 200 to 570 MJ m-2) and dry matter (from 230 to 650 g m-2). As no treatment reached full radiation interception, manipulation of densities  appears as a viable option to increase dry matter production in this species. References Flenet, F., Kiniry, J. R., Board, J. E., Westgate, M., Reicosky, D. C. 1996. Agron. J. 88, 185-190. Magr¨ªn, G. O., Hall, A. J., Baldy, C., Grondona, M. O. 1993. Agric. For. Met. 67, 29-41. Mujica, A., Jacobsen, S.E., Izquierdo, J., Marathee, J. 2001. Resultados de la Prueba Americana y Europea de quinoa. FAO, UNA Per¨², CIP, 51 pp. Sinclair, T. R., Muchow, R. C. 1999. Adv. Agron. 65, 215-265.