Effect of sowing time on yield and agronomic characteristics of wheat in south-eastern Australia

Abstract

The main environmental constraints to the yield of dryland wheat in south-eastern Australia are: a low and erratic rainfall throughout the growing season, the chance of frost at flowering time, and high temperatures during the grain-filling period. The aims of this work were threefold. Firstly, to determine which sowing period minimizes these constraints and results in the highest yields. Secondly, what is the optimum flowering time for a given sowing date so that maximum yield is achieved. The third aim was to determine whether any crop characteristic was associated with high yield or may limit yield in the different sowings. The experiments were conducted at three sites in New South Wales that were representative of dry (Condobolin) and cooler and wetter (Moombooldool, Wagga Wagga) sites in the south-eastern wheatbelt. In this study several sets of isogenic material, involving a total of 23 genotypes, that were similar in all respects except for flowering time, were sown early (mid-April and early May), normal (mid to late May) and late (June to mid July). Characteristics of the highest-yielding lines in each experiment are presented. The average flowering time of the highest yielding lines in all sowings had a range of only 12 days at the driest site, but a range of over 20 days at the coolest and wettest site. The optimum anthesis date (day of year, y) was related to sowing date (day of year, doy) at the cooler sites such that: y = 245+0.32 doy (r2 = 0.86) and at Condobolin, y = 253+0.19 doy (r2 = 0.91). Optimum anthesis date expressed in thermal time (�C days) after sowing (y) was related to sowing time (doy) as follows: y = 2709 -8-3 doy (r2 = 0.84). It is suggested that these relationships are likely to be quite robust and should hold true for similar thermal environments in eastern Australia. There was little variation in grain yield between the earliest sowing in mid-April (108 doy) and sowings throughout May (up to 147 doy). Grain yield declined 1.3% per day that sowing was delayed after late May. Aboveground biomass was substantially higher in early sown crops. However, this did not translate into higher yields. From the evidence presented it is argued that the principal reason that greater yields were not obtained in the early sowings, particularly in the April sowing, was the greater competition for assimilates between the growing spike and the elongating stem. It is suggested that a way of overcoming this competition is to genetically shorten the stems of winter wheats. This should capitalize on the considerable advantages in terms of water use efficiency that early sowing offers and result in greater yields. Barley yellow dwarf virus, although present at the cooler, wettest site in one year, was more frequent in the later sowings than in the early sowing and was not likely to have contributed to the lower than expected yields in the early sowings.

Location, Seeding Date, and Variety Interactions on Winter Wheat Yield in Southeastern United States

“…Th e weather conditions observed between anthesis and grain fi lling in 2011 and 2012 could have caused a shorter duration of spike growth and grain-fi lling phases, which have been reported as a cause of low spike weight, seed weight, yield (Subedi et al, 2007;Bassu et al, 2010;Holman et al, 2011) as well as smaller seed (Gomez-MacPherson and Richards, 1995). Higher correlations between yield and kernel weight, as kernel weight losses increase with late seeding, have been reported in various studies (Knott and Talukdar, 1971;Blue et al, 1990;Gomez-MacPherson and Richards, 1995). A positive correlation between yield and kernel weight was observed in fi ve out of eight location-year combinations from this study.…”

“…According to Th iry et al (2002), early planting promotes high tillering during fall and spring which do not result necessarily in a high number of spikes because of competition among tillers while late planting results in more spring than fall tillers that have a low harvest index. When winter wheat is planted early, deeper root growth is favored (Winter and Musick, 1993) resulting in greater water use effi ciency (WUE) and therefore more biomass (Gomez-MacPherson and Richards, 1995). Th e increase in root and vegetative growth has many benefi ts including a well-established crop cover that favors less erosion and runoff , and greater water infi ltration compared to bare soil (Incerti and O'Leary, 1990;Winter and Musick, 1993).…”

“…Early maturing cultivars could also have higher risk for spring freeze stem damage if early planting is chosen (Kelley, 2001). Contrasting with early maturing cultivars, early planting of late maturing cultivars result in high yields (Gomez-MacPherson and Richards, 1995) but late planting might result in low test weight if temperatures during late spring increase above the historic average values (Kelley, 2001).…”

Testing the Temporal Ability of Landsat Imagery and Precision Agriculture Technology to Provide High Resolution Historical Estimates of Wheat Yield at the Farm Scale

“…Conditions may occur where above ground biomass is high which is represented by a high NDVI value in the image, but the actual yield may not be commensurately large [65] due to pest infiltration, disease or if lodging occurs late in the season. While a careful selection of the image acquisition can improve the extrapolation performance of the models, such processes are very difficult to account for in a single image and the improvement of the models is inconsistent.…”

Breeding wheat for drought adaptation: Development of selection tools for root architectural traits

“…In fact, while drought types differ greatly depending on the season and region (Chenu et al, 2011Chenu, 2014), drought adaptation typically involves the interaction of a number of traits related to water utilisation as well with other physiological processes (Slafer, 2003;Fischer and Edmeades, 2010). As a result, breeders and prebreeders are targeting other traits such as adapted phenology (Gomez-Macpherson and Richards, 1995), transpiration efficiency , cooler canopy temperature (Blum et al, 1989;Olivares-Villegas et al, 2007;Rebetzke et al, 2012b) and reduced tillering (Mitchell et al, 2012). While deep root architecture is likely important for adaptation in rainfed wheat production systems relying heavily on stored soil moisture (particularly at depth, Manschadi et al, 2006), this trait may be less advantageous in other environments, for example where rainfall is more frequent through the growing season, where soils are compacted (Rich and Watt, 2013) or for late sown conditions (Saxena et al, 2014).…”