Winter Wheat Yield Response to Plant Density as a Function of Yield Environment and Tillering Potential: A Review and Field Studies

Abstract

Wheat (Triticum aestivum L.) grain yield response to plant density is inconsistent, and the mechanisms driving this response are unclear. A better understanding of the factors governing this relationship could improve plant density recommendations according to specific environmental and genetics characteristics. Therefore, the aims of this paper were to: i) execute a synthesis-analysis of existing literature related to yield-plant density relationship to provide an indication of the need for different agronomic optimum plant density (AOPD) in different yield environments (YEs), and ii) explore a data set of field research studies conducted in Kansas (USA) on yield response to plant density to determine the AOPD at different YEs, evaluate the effect of tillering potential (TP) on the AOPD, and explain changes in AOPD via variations in wheat yield components. Major findings of this study are: i) the synthesis-analysis portrayed new insights of differences in AOPD at varying YEs, reducing the AOPD as the attainable yield increases (with AOPD moving from 397 pl m -2 for the low YE to 191 pl m -2 for the high YE); ii) the field dataset confirmed the trend observed in the synthesis-analysis but expanded on the physiological mechanisms underpinning the yield response to plant density for wheat, mainly highlighting the following points: a) high TP reduces the AOPD mainly in high and low YEs, b) at canopy-scale, both final number of heads and kernels per square meter were the main factors improving yield response to plant density under high TP, c) under varying YEs, at per-plant-scale, a compensation between heads per plant and kernels per head was the main factor contributing to yield with different TP.

Wheat Grain Yield Response to Seed Cleaning and Seed Treatment as Affected by Seeding Rate During the 2018–2019 Growing Season in Kansas

“…Seeding rate is important within the context of attaining potential yields because it defines the first yield component: plant population. A recent review of winter wheat response to seeding rate suggested that the optimum seeding rate depended on yield environment (Bastos et al, 2020). Grain yield was independent of population in highyielding environments (e.g., high fertility sown at the appropriate time, where tillering is abundant); and higher seeding rates were required in lower-yielding environments (e.g., where the crop does not have as much time to tiller) to improve grain yield (Bastos et al, 2020).…”

“…A recent review of winter wheat response to seeding rate suggested that the optimum seeding rate depended on yield environment (Bastos et al, 2020). Grain yield was independent of population in highyielding environments (e.g., high fertility sown at the appropriate time, where tillering is abundant); and higher seeding rates were required in lower-yielding environments (e.g., where the crop does not have as much time to tiller) to improve grain yield (Bastos et al, 2020). Similar results were reported by Fischer et al 2019and Lollato et al (2019) suggesting an insensitivity of wheat to seeding rate in high-yielding environments; and by Jaenisch et al (2019) suggesting that higher seeding rates were required in lower-yielding environments.…”

“…Not all seeded seeds become an emerged plant. In fact, Bastos et al (2020) suggested that the ratio of achieved over target plant density ranged from 60 to 100% in nine Kansas experiments. Factors that might impact this ratio include seed quality and seed treatment (Pinto et al, 2019).…”

Wheat Variety-Specific Grain Yield Response to Plant Density Under Intensive Management Conditions in Western Kansas

“…The quadratic response suggests that there is an optimum population below which the crop is limited by the number of plants and thus, by its yield components (Whaley et al, 2000); and above which other factors such as disease pressure, insects, lodging, or insufficient resources might limit yield (Lloveras et al, 2004). Recently, a comprehensive analysis of winter wheat yield response to plant density suggested that it depends on the level of resource availability of the environment (Bastos et al, 2020). In high-yielding environments (greater than 90 bushels per acre) where the crop is not limited by resources (including fertility levels, temperature, and moisture for tillering), crop yield was unresponsive to plant population.…”

“…Similar results were derived from the Kansas Wheat Yield Contest and from studies with intensively managed wheat in Kansas (Jaenisch et al, 2019) and in Mexico (Fischer et al, 2019). Meanwhile, in average-(65 bushels per acre average) and low-(45 bushels per acre average) yielding environments, wheat responded to increases in plant population up until the increase of approximately 25-31 plants per square feet (approximately 1.1-1.35 million plants per acre), leveling out at greater populations (Bastos et al, 2020).…”