Contribution of enhanced growth rate and associated physiological changes to yield formation of oats

Peltonen

1997

Self Cite

Spring cereals are commonly sown at high rates in Finland with the result that, under long day conditions, tillering is suppressed. If the apical dominance maintained by the shoot apex can be broken through altered crop management the possibility exists that the increased tillering allows a reduction in seeding rate. Tbe objective of our study was to assess the effects of mechanical and chemical treatments, aimed at breaking the uniculm growth habit, on changes in green leaf area and consequently on biomass accumulation and partitioning in two spring oat, two spring barley, and two spring wheat cultivars. Results indicated that single apphcations of gibberellic acid (GA3), chlormequat chloride (CCC), and urea had no overall, persistent, advantageous effect on crop growth, even though occasional, temporary increases in LAI, and accumulation and partitioning of biomass, were recorded. Changes in crop structure, however, did not solely result from the increased contribution of tillers; treatments also accelerated main shoot growth. Following damage to the main shoot caused by mechanical treatments in particular, one of the tillers rapidly replaced the main shoot. Therefore, a low seeding rate associated with treatments aiming at breaking apical dominance cannot substitute for a high seeding rate at high latitudes. This was particularly the case in 1992 when early summer drought prevalent in southern Finland resulted in peak values of LAI as low as ^ 2 for wheat and ^ 3 for oats and barley.

Section: Discussionsupporting

confidence: 88%

Section: Discussionmentioning

confidence: 99%

Breaking Uniculm Growth Habit of Spring Cereals at High Latitudes by Crop Management. I. Leaf Area Index and Biomass Accumulation

Peltonen

1997

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“…It was postulated that a combination of early maturity and late, rapidly proceeding senescence would accelerate grain and head-filling until late post-anthesis (Peltonen-Sainio, 1993). This was achieved using high N fertilizer rates in exps 1 and II and green manuring in exp 11, without an association with later maturity (Figs 2 and 3).…”

Section: Crop Management Effects On Duration Of Green Leaf Areamentioning

confidence: 99%

Crop Management Effects on Pre‐and Post‐Anthesis Changes in Leaf Area Index and Leaf Area Duration and their Contribution to Grain Yield and Yield Components in Spring Cereals

Forsman

Poutala

1997

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Seasonal changes in leaf area index (LAI) and leaf area duration (LAD, i.e. LAI integrated over cumulated degree days) have a marked effect on crop productivity. Three case experiments were conducted at Suitia (60°irN) and Viikki (60'13'N) Experimental Farms, University of Helsinki, Finland, to evaluate the possibilities of accelerating pre-anthesis expansion of leaf area and modifying pre-and post-anthesis LAD in spring cereals through crop management. Effects of time of incorporation of a green manure crop residue into the soil [conventional tillage (autumn ploughing and seed bed preparation in the spring), conservation tillage (sole spring tillage) with and without a green manure crop, common vetch {Vicia sativa l.)]and N fertilizer rate (0, 50, 100 kg N ha ') on LAI and pre-and post-anthesis LAD in wheat {Triticum aestivum L.) were studied in exp I; green manuring (common vetch) and N fertilizer rate (0,40, 70, 110, 150 kg N ha^') in barley {Hordeum vulgare L.), oat {Avena sativa L.), and wheat in exp II; and fohar application of chlormequat chloride (CCC) and ethephon in oat lines (dwarf, naked, modern, landrace) differing in canopy structure in exp III. Time of incorporation of the green manure crop residues into the soil (exp I), green manuring (exp II), N fertilizer rate (exps I and II), and selection for crop growth type (exp III), but not CCC and ethephon, modified LAI and LAD in spring cereals by affecting the rate of pre-anthesis expansion and postanthesis reduction in leaf area rather than by markedly prolonging the growth period. High rates of N fertilizer accelerated expansion of leaf area, especially prior to stem elongation, and resulted in high pre-anthesis LAD due to enhanced tiller growth (exps I and II) and more tillers per main shoot (exp I). Green manuring increased leaf expansion from the tillering stage most when combined with high N rate, and especially in barley (exp II), but no such effects were found in exp I. Use of a high N fertilizer rate (exps I and 11) and green manuring (exp II) also resulted in high post-anthesis LAD. Such modifications enabled higher rates of grain-and head-filling. and in exp 1 contributed to increased head weight and grain yield. Selection for inherent differences in growth type provided an additional possibility for manipulation of canopy structure and yield fonnation.

“…Moreover, PELTONEN-SAINIO '^ Correspondence to Dr P. Peltonen-Sainio (1991a) showed that grain :straw ratio has reached its optimum of 55 % in oats in Finland. Some oat breeding lines with a HI as high as 60 % were low yielding, probably because of the reduced ability of the stunted vegetative phytomass to produce sufficient amounts of photoassimilates for adequate grain-filling (PELTONEN-SAINIO 1991a).…”

Section: Introductionmentioning

confidence: 99%

Effects of Seeding Rate on Growth Duration and Accumulation and Partitioning of Dry matter in Oats

Järvinen

1994

Self Cite

Crop management influences considerably the three components of grain yield, growth duration, growth rate, and harvest index (HI). Effects of seeding rate on these yield components in oats (Avena sativa L.) was assessed in field experiments at the Viikki Experimental Farm, University of Helsinki, Finland (60°13′N) in 1991 and 1992. Three Finnish oat genotypes were evaluated; a long‐strawed landrace cultivar, a moderately long‐strawed modern cultivar, and a semi‐dwarf breeding line. The following traits were measured: grain yield, days from sowing to yellow ripeness, number of tillers on main shoot, phytomass, vegetative phytomass, and their growth rates (PGR and VGR, respectively), panicle weight and its filling rate (PFR), HI, leaf area index (LAI), and at intervals, dry‐matter accumulation in leaves and straw. Increases in seeding rate significantly decreased growth duration and PGR of individual plants but increased PGR on a ground area basis. Seeding rate did not, however, affect HI. When seeding rate was increased from 200 seeds m−2 to 500 seeds m−2, reductions in vegetative phytomass, panicle weight, VGR, and PFR for individual plants ranged between 20 and 40 %, depending on genotype. At ≥600 seeds m−2 differences in these components between seeding rates were modest. However, PGR, VGR, and PFR per unit ground area increased with increasing seeding rates up to 600–700 seeds m−2. Moreover, the higher the seeding rate, the higher the peak LAI (2.7 maximum) and the earlier the canopy closure. Hence, our results showed that a seeding rate of 600–700 seeds m−2, which resulted in uniculm growth habit, is advantageous in terms of grain yield at high latitudes due to higher biomass accumulation and subsequently greater interception of PAR.