Mechanisms of Yield Loss in Maize Caused by Weed Competition

• Published in: Weed science 2012-04, Vol.60 (2), p.225-232
• Main Authors: Cerrudo, Diego, Page, Eric R, Tollenaar, Matthijs, Stewart, Greg, Swanton, Clarence J
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Carbohydrates; Cereal crops; Competition; Corn; Crop harvesting; Crop science; crop-weed competition; Dry matter; Dry matter accumulation; early development; Energy crops; field experimentation; Field tests; Flowering; Fundamental and applied biological sciences. Psychology; Genetics; glyphosate; Grain; grain yield; Grasses; Growth rate; Harvest index; herbicide resistance; hybrids; kernel number; kernel weight; Leaves; Parasitic plants. Weeds; photosynthetically active radiation; Phytopathology. Animal pests. Plant and forest protection; plant-to-plant variability; Planting density; Plants; seeds; Standard deviation; Triticum aestivum; Vegetation canopies; WEED BIOLOGY AND ECOLOGY; Weed competition; Weed control; Weeds; Winter wheat; Zea mays
• ISSN: 0043-1745; 1550-2759
• DOI: 10.1614/WS-D-11-00127.1

The physiological process underlying grain yield (GY) loss in maize as a result of weed competition is not understood clearly. We designed an experiment to test the hypotheses that early season stress caused by the presence of neighboring weeds will increase plant-to-plant variability (PPV) of individual plant dry matter (PDM) within the population. This increase in PPV will reduce GY through a reduction in harvest index (HI). Field experiments were conducted in 2008, 2009, and 2010. A glyphosate-resistant maize hybrid was cropped at a density of 7 plants m−2. As a model weed, winter wheat was seeded at the same time as maize and controlled with glyphosate at the 3rd or 10th to 12th leaf-tip stage of maize. Weed competition early in the development of maize decreased PDM and GY. This reduction in PDM, which occurred early in the development of maize, was attributed initially to a delay in rate of leaf appearance. Reductions in PDM were accompanied by an increase in PPV of PDM. This increase in PPV, however, did not reduce HI and did not contribute to the GY reductions created by weed competition, as hypothesized. As weed control was delayed, a reduction in fraction of photosynthetically active radiation (fIPAR) accounted for a further reduction in PDM and notably, a reduction in DMA from 17th leaf-tip stage through to maturity. The rapid loss of PDM and the subsequent inability to accumulate dry matter during maturation accounted for a rapid decline in kernel number (KN) and kernel weight (KW). Nomenclature: Glyphosate; maize, Zea mays L. ZEAMX; winter wheat, Triticum aestivum L. TRZAW.