Effects of preceding crop, sowing date, N fertilization and fluquinconazole seed treatment on wheat growth, grain yield and take-all
Einfluss von Vorfrucht, Aussaattermin, N-Düngung und Saatgutbehandlung mit Fluquinconazol auf die Entwicklung und den Kornertrag von Weizen sowie den Befall mit Schwarzbeinigkeit
K. Sieling1,*, K. Ubben1 & O. Christen2
1 Institute of Crop Science and Plant Breeding, University of Kiel, Hermann-Rodewald-Str. 9, D-24118 Kiel, Germany
2 Institute of Agricultural and Nutritional Sciences, University of Halle-Wittenberg, D-06099 Halle/Saale, Germany
* Corresponding author, e-mail sieling@pflanzenbau.uni-kiel.de Received 16 January 2007; accepted 3 April 2007
Summary
The soil-borne fungus Gaeumannomyces graminis var. tritici (Ggt) causing take-all in wheat, barley and rye is regarded as the most important disease on wheat in short rotations with a high proportion of cereals. In 1996/97–1998/99, winter wheat was grown in a field trial with two preceding crops (oilseed rape (OSR) vs. winter wheat), two sowing dates (end of September vs. end of October), eight mineral nitrogen (N) fertilizer treatments (0–200 kg N ha–1) and fluquinconazole seed treatment (no vs. yes), which was carried out at the Hohenschulen Experimental Station near Kiel in NW Ger- many. Tiller numbers m–2, biomass m–2, grain yield, and yield components at harvest of wheat (cv. Toronto) were investigat- ed. During the growing season, the incidence of take-all caused by Ggt was rated on a scale of 1-9.
Averaged over all years and all other treatments, wheat following OSR achieved 8 t ha–1, whereas wheat following wheat yielded 1 t ha–1 (13%) less compared with wheat after OSR, due to a reduction of all yield components. A delay of the sowing date only marginally decreased grain yield by 0.2 t ha–1. N fertilization increased grain yield after all preceding crop combinations, but at different levels. Fluquinconazole seed treatment augmented yield by 0.05 t ha–1 in the first wheat and by 0.11 t ha–1 in the second wheat. Take-all occurred at a very low level in all three years (2.2–3.2). Wheat as preceding crop significantly increased Ggt severity at matu- rity from 2.3 (after OSR) up to 3.2, whereas fluquinconazole seed treatment reduced take-all by 0.2 units. Disease progress curves based on the sum of degree-days since sowing (base:
0°C) revealed a very low Ggt infestation at the end of autumn growth and at the beginning of spring growth, but a progres- sive increase developed throughout the further growing season. Based on the data of wheat following wheat and fer- tilized with 0 or 40 kg N ha–1, a relationship between disease rating and grain yield was established using a linear-plateau function, which indicates yield penalties if Ggt rating exceeds 2.5 units at maturity. Since the preceding crop not only chang- es the inoculum of take-all but other parameters like soil structure, weed infestation, nutrient status, amount and com- position of residues etc., the possibility of chemical control of Ggt allows to study the fungus without altering the plant environment.
Key words:fluquinconazole seed treatment, N fertilization, preceding crop, sowing date, take-all,Triticum aestivum, yield
Zusammenfassung
Der bodenbürtige Pilz Gaeumannomyces graminis var. tritici (Ggt), der Schwarzbeinigkeit an Weizen, Gerste und Roggen verursacht, wird als die wichtigste Krankheit von Weizen in
engen Fruchtfolgen mit einem hohen Getreideanteil ange- sehen. In den Vegetationsperioden 1996/97–1998/99 wurde auf dem Versuchsgut Hohenschulen bei Kiel (Schleswig- Holstein) ein Feldversuch mit Winterweizen (cv. Toronto) durchgeführt, in dem zwei Vorfrüchte (Winterraps vs. Winter- weizen), zwei Aussaattermine (Ende September vs. Ende Oktober), acht Stickstoffstufen (0–200 kg N ha–1) und der Einsatz von Fluquinconazol als Saatgutbehandlungsmittel getestet wurden. Während der Vegetationsperiode wurden die Anzahl der Triebe je m2 und die Trockenmassebildung untersucht. Zur Ernte wurden der Kornertrag und die Ertrags- struktur erfasst. Zu allen Untersuchungsterminen erfolgte eine Bonitur des Befalls mit Schwarzbeinigkeit auf einer Skala von 1-9.
Im Mittel der Jahre und der übrigen Versuchsfaktoren rea- lisierte Weizen nach Raps 8 t ha–1, während vom Weizen nach Weizen einen um 1 t ha–1 (13%) geringeren Ertrag geerntet wurden. Die Ertragseinbußen beruhten auf einer Reduktion aller drei Ertragskomponenten (Ährenzahl je m2, Kornzahl je Ähre, Tausendkornmasse). Eine verspätete Aussaat reduzierte den Ertrag lediglich um 0.2 t ha–1. Die N-Düngung erhöhte den Kornertrag nach beiden Vorfrüchten, allerdings auf unter- schiedlichem Niveau. Eine Saatgutbehandlung mit Fluquinco- nazol steigerte den Ertrag des Weizens nach Raps um 0.05 t ha–1 und den des Weizens nach Weizen um 0.11 t ha–1. In allen drei Jahren trat Schwarzbeinigkeit nur in geringem Maße (2.2–3.2 zur Ernte) auf. Im Vergleich zu Raps (2.3) steigerte die Vorfrucht Weizen den Ggt-Befall auf 3.2. Der Einsatz von Fluquinconazol senkte den Befall um 0.2 Bonitur- stufen. Der Befallsverlauf in Abhängigkeit der Temperatur- summe seit Aussaat (Basis: 0°C) zeigte einen geringen Befall vor und nach Winter, der aber im weiteren Verlauf progressiv zunahm. Die Befalls-Verlust-Relation wurde für Weizen nach Weizen in den ungedüngten bzw. mit 40 kg N ha–1 gedüngten Varianten mittels einer Linear-Plateau-Funktion geschätzt.
Danach ist mit Ertragseinbußen zu rechnen, wenn der Ggt-Be- fall zur Ernte den Wert von 2.5 überschreitet. Da die Vorfrucht nicht nur das Erregerinokulum, sondern auch noch andere Pa- rameter wie Bodenstruktur, Verunkrautung, Nährstoffhaus- halt, Menge und Zusammensetzung der Ernterückstände etc.
beeinflusst, eröffnet die chemische Kontrolle von Ggt mittels Saatgutbehandlung die Möglichkeit, den Erreger zu unter- suchen, ohne die Umwelt der Pflanze zu verändern.
Stichwörter:Aussaattermin, Ertrag, Fluquinconazol- Saatgutbehandlung, N-Düngung, Schwarzbeinigkeit, Triticum aestivum, Vorfrucht
1 Introduction
In the last decades, the acreage of wheat has increased consid- erably due to higher gross margins compared to other crops.
In consequence, wheat is grown after wheat instead of favor-
able preceding crops like oilseed rape (OSR), legumes, or sugar beet. Many studies have demonstrated that wheat as a preceding crop decreased grain yield of a subsequent wheat crop by 8 to 57% compared to a non-wheat crop, depending on site, weather conditions, and crop management (e.g.
ZIMMERMANN 1984; WIDDOWSON et al. 1985; PREW et al. 1986;
MCEWEN et al. 1989; CHRISTEN 1998). The results of CHRISTEN
(1998) and SIELING et al. (2005) indicated the yield reduction being mainly due to a lower number of ears m–2 and a reduced thousand grain weight. Several reasons for the yield decrease are discussed, e.g. exhaustion of nutrient(s), negative changes in the soil structure, a reduced nutrient transformation poten- tial due to a lower activity of the soil microorganisms, occur- rence of weeds (grasses), pests or diseases, and release of phytotoxic substances.
The soil-borne fungus Gaeumannomyces graminis var. tritici (Ggt) causing take-all in wheat, barley and rye can be regard- ed as the most important disease on wheat in short rotations with a high cereal percentage. During early phase of the epi- demic, diseased plants produce more roots than their non-in- fected counterparts. However, as the epidemic progresses, the rate of root production for infected plants slows so that by the end of the epidemic and depending on inoculum density, infected plants have fewer roots than uninfected plants (BAILEY
and GILLIGAN 2004). On the other hand, results of SPINK et al.
(2002) suggest that Ggt does not affect the total size of the root system, but the proportion of diseased and consequently inefficient roots. In experiments with 15N SCHOENY et al.
(2003) found a reduction in N uptake by root segments located below lesions longer than 1 cm on average by half compared with that in healthy roots or root segments above lesions.
Severely infected plants tried to compensate for the reduction of efficient root biomass in order to satisfy shoot N demand by increasing the N uptake rate per unit of efficient root. However, compensation was insufficient. According to investigations of CLARKSON et al. (1975), the crucial stage of lesion development with regard to root function is the invasion and breakdown of phloem by hyphae which reduces the nutrient translocations to roots. BALOTA et al. (2005) stated that the impact of Ggt inoculation on plant growth and leaf carbon assimilation rate may be through reduced photosynthetic capacity of the leaves and not drought stress per se. The authors suggest nutrient deficiency and other enzymatic and hormonal changes within the plant as a result of infection being involved in the reduction of photosynthetic capacity. They conclude that, the reduction in plant growth under take-all cannot be overcome by increased water supply but perhaps can be mitigated by fertilization. If more than 30% of the root system is destroyed, severe yield losses have to be expected (ASHER and SHIPTON 1981; SIELING
1987; SIELING and HANUS 1992; HORNBY 1998).
SPINK et al. (2002) and BAILEY et al. (2006) distinguished two phases of infection. During the primary phase the fungus infects for the first time the (seminal) roots, depending mainly on the inoculum density left by the preceding crop and on soil temperature, since temperature demand of Ggt is higher than that of wheat. In experiments of GUTTERIDGE and HORNBY
(2003) soil infectivity, as measured by a soil bioassay for the take-all fungus, was consistently greater in the sequence of early-sown crops than in the sequence of later-sown crops, although the difference was never significant at the 5% level.
The secondary infection is characterized by the infection of both seminal and adventitious roots starting from the first infection (BAILEY et al. 2006).
Crop husbandry can affect fungal development. Early sow- ing increased disease frequency via primary infection cycle (SCHOENY and LUCAS 1999; SPINK et al. 2002; GUTTERIDGE and HORNBY 2003). According to COLBACH et al. (1997), primary infection and earliness of disease onset were increased by high plant density, however, at late stages no effect was observed.
High N amounts increased both take-all on seminal roots and severity of primary infection, but decreased take-all on nodal roots and secondary infection cycle. Ammonium application
(vs. ammonium nitrate) reduced take-all level (HORNBY and GORING 1972; MACNISH and SPEIJERS 1982).
Since approximately 1995, two fungicides applied as seed treatment are available to affect Ggt: silthiofam (Latitude®) and fluquinconazole (Jockey®). In experiments of BATEMAN et al. (2006) both decreased take-all and increased yields when applied to either second or third wheat crops. Silthiofam de- creased take-all during spring more than did fluquinconazole through delaying primary infection of seminal roots from inoculum in the soil and effective control of early disease (SCHOENY and LUCAS 1999; SPINK et al. 2002). In contrast fluquinconazole usually controlled the development of severe take-all in the summer (secondary or root to root infection) more effectively compared to silthiofam (BATEMAN et al.
2006). It reduced take-all severity, but not number of infected plants (incidence) (BATEMAN et al. 2004).
The objective of our experiment was to test the effects of varying crop husbandry like sowing date, N fertilization, and fluquinconazole on take-all progress, crop growth and grain yield of winter wheat. The obtained data should allow to define a threshold for a tolerable Ggt infection at harvest with- out yield penalties.
2 Materials and methods 2.1 Site and soil
The experiment was carried out on a pseudogleyic sandy loam (luvisol: 160 g kg–1 clay, pH 6.6, 11 mg kg–1 P, 16 mg kg–1 K, 13 g kg–1 Corg,) at the Hohenschulen Experimental Farm (10.0° E, 54.3° N, 30 m a.s.l.) of the Kiel University, located in NW Germany 15 km west of Kiel (Schleswig-Holstein).
The climate of NW Germany can be described as humid. Total rainfall averages 750 mm annually at the experimental site, with ca. 400 mm received during April – September, the main grow- ing season, and ca. 350 mm during October – March (Table 1).
2.2 Treatments and design
In the growing seasons 1996/97–1998/99, winter wheat (cv.
Toronto) was grown following either winter oilseed rape (OSR) or winter wheat as preceding crop.
Two sowing dates were tested. The early sowing date was aimed at the second decade of September (seeding rate:
280 kernels m–2), the late one was performed about 4 weeks later (seeding rate: 360 kernels m–2). Depending on the weather conditions, the exact dates differed between the years (Table 2). Ploughing and seed bed preparation was usually carried out within one day before sowing.
Nitrogen (calcium ammonium nitrate with 27% N) was applied as a split-dressing at beginning of spring growth (GS 25; growth stages according to ZADOKS et al. 1974), at start of stem elongation (GS 30/31), and at ear emergence (GS 50/51). N fertilization varied in amount (0–200 kg N ha–1) and distribution (Table 3).
Seed was treated either with conventional seed treatment (fludioxonil + tebuconazole, trade name: Arena C® in 1996/97; fenfuram + guazatin, trade name: Panoction Spezial® in 1997/98 and 1998/99) or with conventional seed treatment plus fluquinconazole (trade name: Jockey®), ap- plied at a rate of 75 g a.i. (100 kg of seed)–1.
Practical constraints required the field trial design to be a strip-plot design. The preceding crops and the sowing dates represented the two strips. Within the plots of the preceding crop by sowing date interaction, N fertilization and seed treat- ment were randomly distributed with four replications, giving 256 plots per year in total.
Crop management not involving the treatments (e.g.
application of herbicides, fungicides, insecticides and plant regulators) was according to standard farm practice. The
sub-sub-plot size was 12 m x 3 m, using an area of 3 m x 3 m for plant sampling.
2.3 Plant sampling and disease assessment
In order to determine the crop development during the growth period, plants of all plots were sampled from 2 x 0.5 m drilling rows on six dates (four dates in 1998/99) (Table 2). In order to assess disease severity, roots of all wheat plants (7000–7500 plants per date) were gently washed from a
1 mm sieve to remove adhering soil within the same day. The severity of G. graminis var. tritici was visually assessed depend- ing on the proportion of discoloration of the root system colo- nized by the fungus using a scale from 1 (no visible symptoms) to 9 (root system totally destroyed) (MIELKE 1974). Due to the large number of plants, sampling occurred within one week.
After disease assessment, total number of plants and tillers, and total above ground dry matter were measured. Averaged for each plot, single tiller weight was calculated from these parameter. At maturity (GS 91), the number of ears and the thousand grain weight were determined. If necessary, data were standardized to g m–2 or number m–2.
At harvest, an area of 9 m2 was harvested by a combine and yield was standardized to t ha–1 (86% dry matter) based on the moisture content of a grain subsample.
2.4 Statistical analysis
Analyses of variance were done by using proc GLM of the SAS statistical package. The year was used as a blocking factor.
LSD0.05 for preceding crop combination is based on year x pre- ceding crop combination interaction, that for sowing date is based on year x sowing date interaction effects, that for pre- ceding crop x sowing date interaction is based on year x pre- ceding crop x sowing date interaction. Mineral N treatments and seed treatment are based on residual effects. The LSD0.05 applies only to individual treatment means.
Table1:Monthly rainfall (mm) and mean air temperature (°C) at Hohenschulen, Germany
Mean air temperature (°C) Total rainfall (mm)
1996/97 1997/98 1998/99 30-yr mean 1996/97 1997/98 1998/99 30-yr mean
September 12.1 13.5 13.8 13.4 49 55 48 66
October 9.5 8.2 9.0 9.6 58 68 159 60
November 4.7 4.1 2.4 5.4 97 25 74 76
December –0.6 2.9 1.3 2.4 37 58 63 74
January –1.6 3.5 3.2 0.7 3 95 74 62
February 4.3 5.2 1.2 0.7 88 15 53 45
March 4.9 5.0 5.0 3.0 51 50 77 46
April 6.3 8.0 8.2 6.7 27 95 27 49
May 10.8 12.7 12.0 11.3 88 35 48 51
June 15.4 15.1 14.2 15.2 71 85 62 62
July 17.7 15.2 18.1 16.4 123 109 78 77
August 20.7 15.7 16.8 16.3 56 61 83 86
Table2:Sowing and plant sampling dates of winter wheat in the years 1996/97–1998/99 at Hohenschulen experimental station (NW Germany)
Year 1996/97 1997/98 1998/99
Sowing date
Early sowing 19/09/1996 18/09/1997 21/09/1998 Late sowing 16/10/1996 16/10/1997 19/10/1998 Plant sampling
Before winter† Week 46 (548/–)#
Week 47 (516/–)
n.d.‡
Start of spring growth
Week 11 (857/571)
Week 10 (931/607)
Week 10 (749/458) Stem elongation
(GS 30/31)
Week 19 (1184/895)
Week 18 (1331/1006)
Week 17 (1085/795) Ear emergence
(GS 50/51)
Week 24 (1654/1367)
Week 23 (1781/1457)
Week 23 (1584/1293) Milk ripe stage
(GS 75)
Week 29 (2208/1922)
Week 29 (2376/2052)
n.d.
Harvest (GS 90/91)
Week 33 (2758/2472)
Week 32 (2720/2396)
Week 30 (2390/2099)
† Only early sowing treatment.
‡ Not determined.
# Sum of degree-days since sowing (°Cd, base: 0°C) for the early/
late sowing date.
Table3:Amount and application time of the N fertilizer (kg N ha–1) at Hohenschulen experimental station (NW Germany)
Time of application Beginning of
growth in spring
Beginning of stem elongation
(GS 30/31)
Ear emergence (GS 50/51)
Total amount
N1 0 0 0 0
N2 40 0 0 40
N3 0 40 40 80
N4 40 0 40 80
N5 40 40 40 120
N6 40 80 40 160
N7 80 40 40 160
N8 80 80 40 200
Before statistical analysis, disease rating of the single plants were averaged within each plot. Take-all progression curve was fitted to the disease assessment data using the de- gree-days since sowing (base 0°C). In order to relate disease rating to the yield losses, a linear-plateau model was fitted to the crop data on average values across the years:
Y = Ymax – a(DR – C) if DR > C
(1)
Y = Ymax if DR ≤ C
where Y = grain yield (t ha–1); DR = disease rating; C is the disease rating at the intersection of the plateau and the linear model. Ymax describes the plateau (t ha–1). a is a constant, which was estimated using the NLIN procedure of SAS.
3 Results
3.1 Grain yield and yield components
Table 4 shows the F values of the factor effects on the combine harvested yields and the yield components. The preceding crops affected combine harvested grain yield (Table 5). Fol- lowing OSR, wheat crop achieved 8.03 t ha–1 compared to 7.06 t ha–1 if the preceding crop was wheat. However, because of the large error term as consequence of the experimental design, the yield difference of 1 t ha–1 was not significant. N fertilization significantly increased grain yield from 4.8 t ha–1 in the unfertilized plots up to 9.1 t ha–1 in the 200 kg N ha–1 treatment (Table 5). In most of the N treatments, differences between the preceding crops varied between 1.0 and 1.2 t ha–1, except the treatments which had received 80 kg N ha–1 in GS 30/31 at the beginning of stem elongation (N6, N8) where OSR outyielded wheat by about 0.5 t ha–1. Sowing date and fluquinconazole seed treatment only slightly affected grain yield.
The analysis of the yield components highlights that wheat as preceding crop compared with OSR as a preceding crop decreased the number of ears m–2, the number of kernels per ear, the thousand grain weight, and, in consequence, the grain yield and the total aerial biomass (based on the plant sam- pling) compared with OSR (Table 6). Differences in grain and straw yield and in above-ground dry matter were significant at P= 0.05. Harvest index was slightly increased in wheat fol- lowing wheat. N fertilization significantly affected all yield components. Compared with the unfertilized control, the first N application at the start of spring growth mainly boosted the ear density, whereas N applied at the beginning of stem elongation increased the number of kernels per ear (N2 vs.
N3, N6 vs. N7).
3.2 Plant development during the growth period
In two years, 1996/97 and 1997/98, plants from the early sown wheat crop were already sampled in autumn. Seed treatment significantly decreased the number of tillers m–2 (Table 7). Since the total above-ground biomass remained Table4:F values of the factor effects on combine harvested yield and yield components at Hohenschulen experimental station (NW Germany)
Combine harvested yield (t ha–1)
Plant sampling yield (g m–2)
Ears m–2 Kernels per ear TGW†
Preceding crop (PC) 7.48 30.78* 4.43 0.75 7.12
Sowing date (SD) 0.31 1.09 2.83 0.25 4.36
Seed treatment (ST) 3.72 0.65 6.74* 0.61 6.24*
N fertilization (N) 1803.28*** 95.84*** 83.50*** 2.29* 32.29***
PC x SD 0.20 13.10 2.62 0.06 0.49
PC x ST 1.16 2.15 2.57 0.68 0.12
PC x N 13.50*** 0.85 1.21 1.07 2.58
† Thousand grain weight.
* Significant at P= 0.05.
*** Significant at P= 0.001.
Table5:Effect of year, preceding crop, sowing date, N fertili- zation, and fluquinconazole seed treatment on combine harvested grain yield of winter wheat (t ha–1) (following oilseed rape = 100) at Hohenschulen experimental station (NW Germany)
Preceding crop
Oilseed rape Winter wheat Mean Year
1997 7.31 6.96 (95) 7.14
1998 8.97 7.97 (89) 8.47
1999 7.38 6.07 (82) 6.71
Sowing date
Mid of September 8.07 7.12 (88) 7.60
Mid of October 7.93 6.89 (87) 7.42
N fertilization (kg N ha–1)
N1: 0/0/0 5.35 4.19 (78) 4.77
N2: 40/0/0 6.90 5.67 (82) 6.28
N3: 0/40/0 7.78 6.65 (85) 7.21
N4: 40/0/40 7.31 6.17 (84) 6.74
N5: 40/40/40 8.73 7.74 (88) 8.25
N6: 40/80/40 9.22 8.63 (94) 8.93
N7: 80/40/40 9.38 8.24 (88) 8.81
N8: 80/80/40 9.40 8.87 (94) 9.13
Fluquinconazole
No 7.98 6.95 (87) 7.47
Yes 8.03 7.06 (88) 7.55
Mean 8.01 7.01 (87)
LSD0.05 for N fertilization: 0.097.
LSD0.05 for preceding crop x N fertilization interaction: 0.138.
All other effects shown here were not significant at P= 0.05.
unaffected, average single tiller dry matter increased due to fluquinconazole treatment. Following OSR, wheat plants developed better compared to those with wheat as preceding crop, however, the differences were not significant at P= 0.05.
No preceding crop x seed treatment interaction occurred.
In comparison to wheat, OSR as preceding crop led to a denser canopy, to higher dry matter accumulation, and to better developed single tillers during the growing season (Table 8). However, the difference were not significant at some dates. Fluquinconazole seed treatment decreased the number of tillers m–2 at most of the sampling dates (except of harvest) (Table 9). In combination with a slight increase in total aerial dry matter, the single tiller dry matter was higher, if fluquinconazole was applied. However, at harvest, the treat- ments did not differ significantly.
3.3 Disease assessment
The occurrence of take-all remained in all years and treat- ments at a relatively low level (Table 10). At harvest, average disease ratings did not exceed the value of 4 based on a scale ranging from 1 to 9. OSR as preceding crop significantly decreased take-all rating by 0.9 units compared to wheat.
Increasing N fertilization and application of fluquinconazole as seed treatment, both reduced disease severity, whereas delaying of plant establishment rendered no effects.
In order to get more detailed information on the develop- ment of take-all during the growing season, disease progres- sion curves were estimated. Before winter and at start of spring growth till ear emergence (1580–1780°Cd) roots of early sown wheat following wheat showed only very few disease symptoms (Fig. 1). Disease severity progressively increased during further crop development. Comparing the preceding crops on average of three years and both sowing dates revealed that take-all spread quicker in the second wheat crop than in wheat following OSR (Fig. 2).
3.4 Relation between take-all and grain yield
In order to estimate the effect of take-all on grain yield, both parameter were related using a linear-plateau model (Fig. 3).
Since increasing N supply may overlay disease effects, only N1 and N2 treatments (total N amount: 0 or 40 kg N ha–1) follow- ing wheat were included (n = 96). The linear-plateau function revealed that yield losses due to take-all have to be expected if disease rating at harvest exceeds 2.5. Increasing take-all severity Table6:Effect of year, preceding crop, sowing date, N fertilization, and fluquinconazole seed treatment on yield and yield components of winter wheat at Hohenschulen experimental station (NW Germany)
Ears m–2 Kernels per ear TGW† (g) Grain yield (g m–2) Straw yield (g m–2) Harvest index Year
1997 526 37.1 43.6 850 754 0.53
1998 506 35.1 45.9 804 787 0.51
1999 414 38.4 41.4 644 718 0.47
Preceding crop
Oilseed rape 503 37.9 44.4 818 838 0.49
Winter wheat 462 35.9 42.9 716 667 0.52
LSD0.05 n.s.‡ n.s. n.s. 34.7 46.6 n.s.
Sowing date
Mid of September 504 36.4 44.3 794 847 0.48
Mid of October 461 37.3 43.0 741 658 0.53
LSD0.05 n.s. n.s. n.s. n.s. n.s. n.s.
N fertilization (kg N ha–1)
N1: 0/0/0 375 32.5 41.9 518 481 0.52
N2: 40/0/0 434 36.1 41.7 653 661 0.50
N3: 0/40/0 425 41.8 44.6 721 650 0.53
N4: 40/0/40 428 35.5 45.5 681 653 0.51
N5: 40/40/40 506 36.4 45.3 828 822 0.50
N6: 40/80/40 559 38.6 43.7 934 921 0.50
N7: 80/40/40 563 36.6 43.9 900 913 0.50
N8: 80/80/40 575 37.5 42.6 911 935 0.49
LSD0.05 22.7 4.87 0.72 41.6 35.2 0.009
Fluquinconazole
No 486 37.4 43.5 771 759 0.50
Yes 479 36.4 43.8 763 748 0.51
LSD0.05 4.9 n.s. 0.23 n.s. n.s. n.s.
Mean 483 36.9 43.6 767 753 0.51
† Thousand grain weight.
‡ Not significant at P = 0.05.
would decrease grain yield by 0.96 t per unit. However, mainly due to a large year to year variation, r2 value of 0.27 was low, although significant at P< 0.0001. The poor relationship also indicates that other factors than take-all affected grain yield.
4 Discussion
In the present study different crop management factors were tested in terms of their effects of growth and yield of winter Table7:Effect of the preceding crop and fluquinconazole seed treatment on tiller density, above-ground dry matter accumu- lation, and single tiller dry matter before winter of early sown wheat in 1996/97 and 1997/98 at Hohenschulen experimental station (NW Germany)
Preceding crop
Fluquin- conazole
Tillers m–2
Above-ground dry matter (g m–2)
Single tiller dry matter (mg)
Oilseed rape no 658 25.3 39.1
yes 590 24.8 44.7
Wheat no 603 22.0 38.4
yes 584 23.1 42.0
Oilseed rape 624 25.0 41.9
Wheat 594 22.6 40.2
LSD0.05 n.s.† n.s. n.s.
no 630 23.6 38.7
yes 587 23.9 43.4
LSD0.05 24.3 n.s. 1.08
† Not significant at P = 0.05.
Effects of preceding crop x fluquinconazole interaction were not significant at P= 0.05.
Table8:Effect of the preceding crop on tiller density, above-ground dry matter accumulation (g m–2), and single tiller weight (mg) during the growth period 1996/97–1998/99 at Hohenschulen experimental station (NW Germany)
Sampling date Preceding crop Start of
spring growth
Beginning of stem elongation
Beginning of ear emergence
Harvest
Dry matter (g m–2)
Oilseed rape 51.7 177.7 986.0 1656.3
Wheat 43.6 150.1 919.4 1383.2
LSD0.05 n.s.† 5.62 32.97 11.98
Tillers m–2
Oilseed rape 1063 1108 514 504
Wheat 947 985 483 461
LSD0.05 45.4 65.2 3.4 n.s.
Single tiller weight (mg)
Oilseed rape 42.2 162.3 1946.3 3296.1
Wheat 40.7 151.2 1919.2 2986.3
LSD0.05 n.s. 5.66 n.s. n.s.
† Not significant at P= 0.05.
Table9:Effect of fluquinconazole seed treatment on above- ground dry matter accumulation (g m–2), tiller density, and single tiller weight (mg) during the growth period 1996/97–
1998/99 at Hohenschulen experimental station (NW Germany) Sampling date
Fluquinconazole Start of spring growth
Beginning of stem elongation
Beginning of ear emergence
Harvest
Dry matter (g m–2)
No 46.3 160.3 948.3 1530.0
Yes 49.1 168.2 957.5 1511.3
LSD0.05 1.15 n.s.† n.s. n.s.
Tillers m–2
No 1042 1079 506 486
Yes 969 1016 492 479
LSD0.05 24.9 37.9 5.1 n.s.
Single tiller weight (mg)
No 38.5 148.4 1906.0 3137.6
Yes 44.4 165.6 1959.6 3146.9
LSD0.05 0.90 3.22 30.09 n.s.
† Not significant at P= 0.05.
Table10:Effect of year, preceding crop, sowing date, N fertiliza- tion, and fluquinconazole seed treatment on take-all rating (1-9) at harvest at Hohenschulen experimental station (NW Germany)
Preceding crop
Oilseed rape Winter wheat Mean Year
1997 2.3 3.5 2.9
1998 2.0 2.4 2.2
1999 2.7 3.7 3.2
Sowing date
Mid of September 2.4 3.2 2.8
Mid of October 2.2 3.2 2.7
N fertilization (kg N ha–1)
N1: 0/0/0 2.5 3.3 2.9
N2: 40/0/0 2.5 3.2 2.8
N3: 0/40/0 2.4 3.7 3.0
N4: 40/0/40 2.3 3.3 2.8
N5: 40/40/40 2.2 3.0 2.6
N6: 40/80/40 2.3 3.1 2.7
N7: 80/40/40 2.2 3.0 2.6
N8: 80/80/40 2.1 3.0 2.6
Fluquinconazole
No 2.4 3.3 2.9
Yes 2.2 3.1 2.7
Mean 2.3 3.2
LSD0.05 for preceding crop: 0.50.
LSD0.05 for N fertilization: 0.16.
LSD0.05 for fluquinconazole seed treatment: 0.09.
LSD0.05 for preceding crop x N fertilization interaction: 0.22.
All other effects shown here were not significant at P= 0.05.
wheat and take-all infection. OSR as a favorable preceding crop increased wheat grain yield by 1 t ha–1 (+13%) compared to wheat (Table 4). This result is in good agreement with other trials dealing with crop rotations or preceding crops performed at the same site (e.g. CHRISTEN 1998; SIELING et al.
2005) and in the range found in differing experiments in NW Europe (e.g. WIDDOWSON et al. 1985; PREW et al. 1986; MCEWEN
et al. 1989). Significant difference in crop growth due to the preceding crop occurred from the beginning of stem elonga- tion until harvest, mainly due to more tillers per plant and partly to higher single tiller weight in the wheat following OSR. The effect of the latter one was not significant at most of the sampling dates. However, already at the end of autumn growth (only determined in early sown wheat) and at the beginning of spring growth wheat following OSR accumulat- ed more aerial biomass than wheat following wheat (Table 7).
Although not significant, these differences together with similar results from other experiments (SIELING et al. 2005) clearly indicate that even in autumn preceding crops effects can occur. Yield losses were due to a reduction in all three yield components (ears m–2, kernels per ear, thousand grain weight) (Table 6). This finding is in contrary to former rota- tion trials, where mainly the ear density and the grain filling were damaged, but seldom the number of kernel per ear (CHRISTEN 1998; SIELING et al. 2005).
Sowing date and fluquinconazole seed treatment (+ 0.05 t ha–1 in the first wheat, +0.11 t ha–1 in the second wheat) only slightly affected grain yield (Table 4). At early sampling dates,
plants treated with fluquinconazole accumulated more above-ground DM (non significant), but they produced less tillers m–2 leading to a higher single tiller weight (Table 7). At harvest, no differences in total DM occurred, neither following OSR nor wheat.
Increasing N supply increased grain yield of the second wheat more than wheat following OSR. N fertilization was chosen to be below the optimum in order to avoid that even the highest fertilizer N amount of 200 kg N ha–1 compensate for the effects of an unfavorable preceding crop. Treatment N6 (40/80/40) achieved higher yields than N7 (80/40/40), although the total amount of fertilizer N was applied. This is in contrast to the general opinion recommending an increased N rate to be applied at the beginning of spring growth (WIDDOWSON
et al. 1985; PREW et al. 1986; CHRISTEN et al. 1992).
The observed yield differences following the preceding crops might have several reasons. The main focus of this investigation was focused on the infection of Ggt, especially because fluquinconazole seed treatment as one experimental factor was assumed to control Ggt. On average, severity of Ggt remained very low with average values at maturity of 2.3 (following OSR) and 3.2 (following wheat) on a scale of 1-9 (Table 10, Fig. 1, Fig. 2). Fluquinconazole seed treatment reduced take-all rating on average by 0.2 units. The relative small effect might be due to the low severity. BATEMAN et al.
(2004, 2006) observed a marked disease reduction and yield increase in moderately and severely infected crops, but not crops with small infections. Since the incidence of Ggt was very low in autumn, take-all would not have negatively affect- ed the plant growth at the early sampling dates. A delay in the sowing date in order to prevent from infections in autumn did not reduce Ggt rating, especially following wheat where it has been expected. Results of SIELING (1987) obtained at the same site revealed a marked reduction in Ggt rating after shifting the sowing date from the 3rd decade of September to the 3rd decade of October being as effective as a favorable preceding crop. In his experiments take-all in late sown wheat following wheat was similar as in early sown wheat following OSR.
The disease progress curves differed between the years, although differences in temperature were leveled out by using the sum of degrees (Fig. 1). The trial was not located on the same field, but changed with the years. Therefore varying primary Ggt inoculums on the fields left by the pre-preceding crop and/or its infectivity presumably caused the observed differences in take-all. Since the disease rating bases on the proportion of diseased roots to the total number of roots sampled, the growth of the plants additionally has to be taken into account, so that plant growth itself might have differed both in field and year. However, due to the experimental design, this hypothesis can not be verified.
Fig. 1: Disease progress curves in different years, based on the sum of degree-days since sowing (base: 0°C, preceding crop: wheat, early sowing date) at Hohenschulen experimental station (NW Germany)
1 2 3 4 5
0 500 1000 1500 2000 2500 3000
Sum of degree-days since sowing (°Cd)
Disease rating (1-9) 1997/98
1996/97 1998/99
Fig. 2: Disease progress curves in wheat following oilseed rape or wheat as preceding crops, based on the sum of degree-days since sowing (base: 0°C) at Hohenschulen experi- mental station (NW Germany)
1 2 3 4 5
0 500 1000 1500 2000 2500 3000
Sum of degree-days since sowing (°Cd)
Disease rating (1-9) Oilseed
rape Wheat Oilseed rape: y=e0.000305, n=36, r2=0.88***
Wheat: y=e0.000429, n=36, r2=0.92***
Fig. 3: Relationship between rating of Gaeumannomyces graminis (scale 1-9) and grain yield (t ha–1) of wheat following wheat (N fertilization: 0 or 40 kg N ha–1; n = 96, r2 = 0.27***) at Hohenschulen experimental station (NW Germany)
0 1 2 3 4 5 6 7 8 9
1 2 3 4 5 6
Disease rating DR (1-9) Yield (t ha–1)
DR<2.33: Y=5.87
DR>2.33: Y=5.87-0,96(DR-2.33)
According to our results take-all exceeding a threshold of 2.5 at maturity will lead to yield losses (Fig. 3). However, a rating of 3 stands for ‘several brown lesions; 2-3 roots yellowed’, indicating that less than 10% of the root system is infected. Against this background this value seems to be extremely low. Previous investigations revealed yield losses at ratings >5 at maturity. The r2-value of the relationship between Ggt rating and grain yield remained low, although only plots of wheat following wheat either without N or fertil- ized with 40 kg N ha–1 were taken into account. SPINK et al.
(2002) achieved similar low r2 when relating the yield improvement to the reduction in Ggt infection.
It should be noted that different preceding crops not only change the inoculum of take-all but also a lot of other para- meters like soil structure, weed infestation, nutrient status, amount and composition of residues etc. so that the separate effects of Ggt are difficult to investigate (SPINK et al. 2002;
BAILEY et al. 2006). The possibility of chemical control of Ggt allows to study the fungus without altering the plant environ- ment. OSR leaves the soil in a favourable structure. Due to its long growth period in combination with an intensive soil covering the weed population remains at a low level. In addi- tion, N availability is increased following OSR compared with wheat as preceding crop. Different management strategies have been discussed to compensate for the yield losses due to unfavourable preceding crops. However, most of the results available in the literature indicate that it is not possible to completely compensate for the detrimental influences of an unfavourable preceding crop on the grain yield of the subse- quent wheat crop by optimizing crop management (PANSE et al. 1994; CHRISTEN 1998).
Acknowledgements
The project was funded by Hoechst Schering AgrEvo GmbH.
Literature
ASHER, M.J.C., P. SHIPTON, 1981: Biology and Control of Take-all.
Academic Press, London, UK.
BAILEY, D.J., C.A. GILLIGAN, 2004: Modeling and analysis of disease-induced host growth in the epidemiology of take-all.
Phytopathology 94, 535-540.
BAILEY, D.J., M. GOSME, P. LUCAS, N. PAVELEY, J. SPINK, N. CUNNIFFE, C.A. GILLIGAN, 2006: Developing a rationale to integrate take-all control measures, reduce disease impact and maxi- mise wheat margins. HGCA project report No. 398.
BALOTA, M., C.M. RUSH, W.A. PAYNE, M.D. LAZAR, 2005: The effect of take-all disease on gas-exchange rate and biomass in two winter wheat lines with different drought response.
Plant Soil 275, 337-348.
BATEMAN, G.L., R.J. GUTTERIDGE, J.F. JENKYN, 2004: Take-all and grain yields in sequences of winter wheat crops testing fluquinconazole seed treatment applied in different combi- nations of years. Ann. Appl. Biol. 145, 317-330.
BATEMAN, G.L., R.J. GUTTERIDGE, J.F. JENKYN, M.M. SELF, J. ORSON, 2006: Optimising the performance and benefits of take-all control chemicals. HGCA project report No. 395.
CHRISTEN, O., 1998: Untersuchungen zur Anbautechnik von Winterweizen nach unterschiedlichen Vorfruchtkombina- tionen. Schriftenr. Inst. Pflanzenbau Pflanzenzücht. No. 7.
CHRISTEN, O., K. SIELING, H. HANUS, 1992: The effect of different preceding crops on the development, growth and yield of winter wheat. Eur. J. Agr. 1, 21-28.
CLARKSON, D.T., M.C. DREW, J.B. FERGUSON, J. SANDERSON, 1975:
The effect of the take-all fungus, Gaeumannomyces grami-
nis, on the transport of ions by wheat plants. Phys. Plant Pathol. 6, 75-84.
COLBACH, N., P. LUCAS, J.-M. MEYNARD, 1997: Influence of crop management on take-all development and disease cycles on winter wheat. Phytopathology 87, 26-32.
GUTTERIDGE, R.J., D. HORNBY, 2003: Effects of sowing date and volunteers on the infectivity of soil infested with Gaeuman- nomyces graminis var. tritici and on take-all disease in suc- cessive crops of winter wheat. Ann. Appl. Biol. 143, 275-282.
HORNBY, D., 1998: Take-all disease of cereals: a regional perspective. CAB International Oxford, UK.
HORNBY, D., C.A.I. GORING, 1972: Effects of ammonium and nitrate nutrition on take-all disease of wheat in pots. Ann.
Appl. Biol. 70, 225-231.
MACNISH, G.C., J. SPEIJERS, 1982: The use of ammonium fertil- isers to reduce the severity of take-all (Gaeumannomyces graminis var. tritici) on wheat in Western Australia. Ann.
Appl. Biol. 100, 83-90.
MCEWEN, J., R.J. DARRY, M.V. HEWITT, D.P. YEOMAN, 1989: Effects of field beans, fallow, lupins, oats, oilseed rape, peas, ryegrass, sunflowers and wheat on nitrogen residues in the soil and on the growth of a subsequent wheat crop. J. Agric.
Sci. (Cambridge) 115, 209-219.
MIELKE, H., 1974: Untersuchungen über die Anfälligkeit ver- schiedener Getreidearten gegen den Erreger der Schwarz- beinigkeit, Ophiobolus graminis Sacc. Mitt. Biol. Bundes- anst. 160.
PANSE, A., F.X. MAIDL, J. DENNERT, H. BRUNNER, G. FISCHBECK, 1994: Ertragsbildung von getreidereichen Fruchtfolgen und Getreidemonokulturen in einem extensiven und intensiven Anbausystem. J Agron. Crop Sci. 173, 160-171.
PREW, R.D., J. BEANE, N. CARTER, B.M. CHURCH, A.M. DEWAR, J. LACEY, A. PENNY, R.T. PLUMB, G.N. THORNE, A.D. TODD, 1986:
Some factors affecting the growth and yield of winter wheat grown as a third cereal with much or negligible take-all. J.
Agric. Sci. (Cambridge) 107, 639-671.
SCHOENY, A., F. DEVIENNE-BARRET, M.-H. JEUFFROY, P. LUCAS, 2003:
Effect of take-all root infections on nitrate uptake in winter wheat. Plant Pathol. 52, 52-59.
SCHOENY, A., P. LUCAS, 1999: Modeling of take-all epidemics to evaluate the efficacy of a new seed-treatment fungicide on wheat. Phytopathology 89, 954-961.
SIELING, K., 1987: Ertragsstruktur von Weizen in Abhängigkeit von den Wechselwirkungen zwischen Produktionstechnik und Wurzelerkrankungen. Ph.D. Thesis, University of Kiel.
SIELING, K., H. HANUS, 1992: Yield of winter wheat influenced by the interactions between crop management measures and take-all. Eur. J. Agr. 1, 201-206.
SIELING, K., C. STAHL, C. WINKELMANN, O. CHRISTEN, 2005: Growth and yield of winter wheat in the first three years of a monoculture under varying N fertilization in NW Germany.
Eur. J. Agr. 22, 71-84.
SPINK, J.H., J.J. BLAKE, J. FOULKES, C. PILLINGER, N. PAVELEY, 2002:
Take-all in winter wheat: Effects of silthiofam (Latitude) and other management factors. HGCA project report No. 268.
WIDDOWSON, F.V., A. PENNY, R.J. GUTTERIDGE, R.J. DARBY, M.V.
HEWITT, 1985: Tests of amounts and times of application of nitrogen and sequential sprays of aphicides and fungicides on winter wheat, and the effects of take-all (Gaeumannomy- ces graminis var. tritici) on two varieties at Saxmundham, Suffolk 1980-3. J. Agric. Sci. (Cambridge) 105, 97-122.
ZADOKS, J.C., T.T. CHANG, C.F. KONZAK, 1974: A decimal code for growth stages of cereals. Weed Res. 14, 415-421.
ZIMMERMANN, A., 1984: Winterweizen in Monokultur – Unter- suchungen über Ertragsbildung, Bestandesstruktur und Krankheitsbefall unter besonderer Berücksichtigung der Befalls-Ertragsrelation bei Halmbasis- und Wurzelerkran- kungen. Ph.D. Thesis, University of Kiel.
