INFLUENCE OF RETARDANTS ON YIELDS AND SOME QUALITY CHARACTERS OF WINTER WHEAT

Danuta Leszczyńska, Grażyna Cacak-Pietrzak

ABSTRACT

A study run in the years 2000–2002 aimed at determining the effect of the kind of redardant, application stage and rate on the yields and quality traits of winter wheat.

Key words: winter wheat, retardants, yields, grain quality..

INTRODUCTION

Retardants play an important role in the system of cereal protection by reducing the risk of lodging. Lodging causes quantitative and qualitative losses of the grain crop. The amount of the loss is, to a great extent, dependent on the degree of lodging and on the date of its occurrence. Under the conditions conducive to lodging, the shortening of the stem by applying growth regulators is the only method that could reduce or eliminate that phenomenon. Investigations on the application of retardants focus mainly on their yield-forming capability. In this study retardant formulation, application rate and application stage were evaluated for their effect on the selected quality traits of winter.

MATERIALS AND METHODS

The study was performed at the IUNG experiment station in Jelcz-Laskowice using Korweta, a winter wheat cultivar frequently grown in Poland. The trials were set up on a soil rated as the good wheat complex. They were run in the years 1999-2002, laid out as randomized split-plot designs including the control treatment with four replications. Retardant formulas (Cycocel 460 SL – chloromequat and Terpal 460 SL – chloromequat + etephon), application date: at full tillering, first and second node stage and application date (maximum and minimum according to the Institute of Plant Protection recommendations) were the experimental factors. For Cycocel 460 SL the maximum rate was 3.5 l/ha, for Terpal 460 SL – 2.5 l/ha. The minimum rates were 2 and 1.5 l/ha, respectively. The fertilization and plant protection practices were typical of the intensive crop management. They included 1–2 herbicide treatments and 2–3 fungicide treatments. Nitrogen was applied at 120 kg N/ha as ammonium nitrate as three applications: 60 kg N/ha at the start of growth, 40 kg/N ha at the shooting stage and 20 kg/ha at the earing stage.

The grain was evaluated for the following physical properties and chemical contents:

• test weight [6],

• weight of 1000 grain [6],

• selectness and uniformity[6],

• glassiness [6],

• total ash content [6],

• total protein contents determined on the Kjel-Foss Automatic (N·5.83),

• quantity and quality of wet gluten in the Glutomatic 2200 (ICC Standard no. 137),

• the Hagberg falling number (ICC Standard no. 107).

The results were subjected to statistical analysis.

RESULTS AND DISCUSSION

The statistical analysis of the results over the years 2000–2002 showed that only in the year 2002 there was a significant effect of the factors under study on the yields of winter wheat. There was an interaction of application date and retardant formula. When applied later than tillering, Cycocel 460 SL significantly reduced the yields whereas the timing of the application of Terpal 460 SL did not affect the grain yield.

At the tillering stage, the application of Cycocel 460 SL was significantly more effective. Instead, at the 1st node stage Terpal 460 SL gave a better effect. Retardant formula, when applied at the 2nd node stage had no significant effect on the yields of winter wheat. In each year, regardless of application date, the retardant formulas caused the yields to increase over the untreated control. However, the weather conditions during the study were not conducive to lodging and because of that the effectiveness of the retardants was lower than expected.

The highest effectiveness in terms of shortening of the stem was achieved by applying the maximum dose of Cycocel 460 SL at the 1st and the 2nd node stage. A similar relationship was observed for Terpal 460 SL, though to a smaller extent.

The bulk density of the grain from the control treatment was relatively high and reached 80.1 kg · hl^-1 (Table 1). Terpal did not influence that trait but Cycocel usually caused its slight decrease. However, the statistically valid reduction of the bulk density of the grain on the control was recorded only following the maximum rate of Cycocel applied at the 2nd node stage. Gruzdjev [5] and Kandera [8] also reported no effect of retardants on the bulk density of grain. The results on the 1000-grain weight as affected by the use of retardants are contradictory. According to Gruzdjev [5] and Pisulewska [10] chlormequat may favourably influence that trait (increase from 2 to 6%), etephon may have the same impact according to Cox and Otis [3]. Instead, the studies by Dziamba [4], Jończyk [7] and by Kuś and Jończyk [9] indicate that single applications of chlormequat may slightly decrease 1000-grain weight (by 1-2%). Joint applications of chlormequat with fungicides may have a similar effect [2, 12].

In this study, there was a tendency for the weight of 1000 grains to decline, regardless of the retardant applied. According to Kandera [8] and to Prusakova and Gruzdjev [11] retardants caused selectness and filling of the grain to decline. In this study they had no significant impact on that trait. Grain glassiness in the control treatment was 45%. Both tested formulas had statistically significant, though irregular, effect on grain structure. On the Cycocel treated plots the glassiness was from 38 to 63%. The Terpal-treated grain showed glassiness values ranging from 41 to 62%, depending on application rate and timing.

The ash content of the grain from the control treatment was 1.73% (Table 2). In the samples from retardant-treated treatments ash content ranged from 1.73 to 1.78 but it did not differ significantly from the control sample.

The protein content of the grain was 13.2% in the control treatment. Cycocel had no effect on the total protein content. The use of Terpal decreased protein content, regardless of rate and timing of the application. A decrease of or inconsistent changes in the content of total protein were also reported by Cichy [2] and by Prusakova and Gruzdjev [11]. A retardant-related increase in total protein was obtained by Brzozowska et al. [1], Dziamba [4], Gruzdjev [5], Pisulewska [10] and by Zając et al. [12]. The gluten content of the grain in the control treatment was 24.5%. In this study, there was a decline in wet gluten content following the application of either retardant but it was generally accompanied by some improvement in gluten quality (increase in the value of gluten indices). A decline in gluten content also occurred in the experiment by Kandera [8] following the application of chlormequat. The grain samples from this study were characterized by a very low activity of amylolytic enzym es (falling numbers from 385 to 429 s.). Cycocel caused the amylolytic activity of grain to decrease (an increase in the value of the falling number) whereas Terpal usually slightly increased the amylolytic activity of the flour.

CONCLUSIONS

1. The formulas applied caused the yields to increase significantly over those from the untreated control regardless of application date.

2. The formula Cycocel 460 SL had a greater impact on the physical properties and the chemical composition of the grain.

3. Both formulas used in the study generally decreased the 1000-grain weight to decrease, lowered the amount of wet gluten while at the same time improving gluten quality and had no effect on selectness and uniformity of grain and on ash content. Additionally, the formula Cycocel decreased bulk density of the grain, lowered total protein content and falling number whereas Terpal 460 SL increased the value of falling number.

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Grażyna Cacak-Pietrzak
Division of Cereal Technology
Warsaw Agricultural University
Nowoursynowska 159c, 02-787 Warsaw, Poland
e-mail: cacak@alpha.sggw.waw.pl

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