Physiological determinants of crop growth and yield in maize, sunflower and soybean. Their application to crop management, modeling and breeding.

F.H. ANDRADE; V.O. SADRAS; C.R.C. VEGA; L. ECHARTE

THE JOURNAL OF CROP IMPROVEMENT

Año: 2005 vol. 14 p. 51 - 101

1542-7528

The knowledge of factors and mechanisms that determine crop growth and yield is critical for an efficient and sustainable production because it i) guides the design and selection of the most appropriate management practices, ii) provides information for efficient and adequate use of agricultural inputs, iii) provides breeders with the conceptual and screening tools that could improve efficiency in the selection of genotypes with high yield potential and adaptation to the target environment and iv) constitutes the conceptual framework for crop simulation models. The first part of the review focuses on the mechanisms determining yield in maize (Zea mays L.), sunflower (Helianthus annus L.) and soybean [Glycine max (L.) Merr], the three major summer crops of the Argentinean Pampas. Crops with axillary (maize) or apical (sunflower) reproductive sinks, or with sequentially developed fruits (soybean) were analyzed using a common comprehensive and simple conceptual framework. Emphasis is given to the capture of light by the crop canopy and the processes determining grain set and grain filling. A tight correlation between grain yield and the physiological status of crops or plants at crop-specific critical periods is confirmed. This section is largely based on our own research. The second section highlights how we use this basic physiological information to evaluate and understand the effect of agricultural management practices on crop yield in the southeastern Pampas. The concepts of yield and harvest-index stability, critical periods for grain yield determination, vegetative and reproductive plasticity among others, constitute the basis for understanding the crop yield as determined by management practices, cultivars, environmental conditions and the interactions among these factors. Plant density, inter-row distance, uniform planting, sowing date, cultivar selection, and fertilization are analyzed relative to their effect on the physiological condition of the crop or the plant within the crop. Management practices should ensure that the crop maximizes radiation interception, crop growth rate, and dry matter partitioning to reproductive structures during the critical period for grain yield determination. The third section deals with the physiology of yield determination as the source of concepts and quantitative relationships for crop simulation models. We highlight the impact of our research as a basis for improving crop simulation models. We also present simple, management-oriented empirical models developed to asses the impact of key environmental and management practices on crop yield in our region. Finally, we discuss the relevance of the described physiological processes for crop breeding. We concentrate on research by our team that compares cultivars released in different eras to quantify the contribution of genetic improvement to crop yield, and to dissect the traits involved in yield improvement. We highlight the value of this approach to understand the effects of genetic improvement on crop yield and to improve the efficiency of future breeding efforts.