DISEASE DEVELOPMENT AND FERTILISER EFFICACY

disease Development and fertiliser efficacy in spring barley

Sigitas LAZAUSKAS and Roma SEMASKIENE

Lithuanian Institute of Agriculture

Summary: Field experiments with the spring barley variety Alsa were conducted during 1996-1999 and the variety Scarlett during 2000-2003 on a loamy soil at the Lithuanian Institute of Agriculture, Kedainiai district. The yield of spring barley was significantly enhanced by the use of fungicides when leaf spot diseases started to spread at the beginning of grain filling. In the case of late, but very severe attack of diseases at the end of grain filling, the use of fungicides also resulted in a significantly higher yield. During the dry growing season the yield of spring barley was not significantly affected by the use of fungicides. In dry years grain yield level was much lower and protein content in grain was much higher, than in the years with a more favourable moisture regime. The positive effect of nitrogen fertilisers on grain yield and protein content in grain was significant almost in all cases. The shape of the nitrogen response curves was rather similar, but resulted in different optimum for nitrogen.

Key words: Spring barley, disease development, nitrogen fertilisers

Souhrn: Byly provedeny polní pokusy s jarním ječmenem na hlinité půdě Litevského zemědělského institutu v okrese Kedainiai v letech 1996-1999 s odrůdou Alsa a v letech 2000-2003 s odrůdou Scarlett. Výnos jarního ječmene byl při použití fungicidů průkazně zvýšen, když se začaly šířit listové choroby na začátku nalévání zrna. V případě opoždění, nebo při velmi silném napadení chorobami na konci nalévání zrna mělo použití fungicidů ale také za následek průkazně vyšší výnos. Během suché vegetace nebyl výnos jarního ječmene při použití fungicidů průkazně ovlivněn. V suchých letech úroveň výnosů zrna byla mnohem nižší a obsah bílkovin byl mnohem vyšší, než v letech s příznivějším vlhkostním režimem. Pozitivní efekt dusíkatých hnojiv na výnos zrna a obsah bílkovin v zrnu byl průkazný téměř ve všech případech. Forma odpovídajících křivek dusíku byla dosti podobná, ale projevilo se odlišné optimum pro dusík.

Klíčová slova: jarní ječmen, rozvoj chorob, dusíkatá hnojiva

Introduction

Barley diseases have many causes and may result in a considerable reduction in grain yields. Losses vary with the nature of the pathogen, the timing and intensity of attack and environmental stresses. Several foliar diseases have serious consequences in malting spring barley production. These are: net blotch (Pyrenophora teres), powdery mildew (Blumeria graminis), spot blotch (Cochliobolus sativus), septoria leaf blotch (Septoria spp.). In addition to reducing yield, diseases (such as septoria leaf blotch) also reduce kernel plumpness and malt extract, which are important malt quality characters (Toubia-Rahme H. & Steffenson B. J., 1999).

Nitrogen fertilization is essential for increasing yield level, however, requirements for limited nitrogen content in grain of malting barley necessitate a very careful determination of nitrogen rate. For this reason optimum rates for malting barley are below those needed to produce maximum grain yield (Birch C.J. et al., 1997).

The aim of this study was to examine disease development and assess nitrogen fertiliser effect on spring barley grown for malt production.

Material and methods

Field experiments were conducted on a loamy soil at the Lithuanian Institute of Agriculture, Kedainiai district during 1996-1999 with the spring barley variety Alsa and during 2000-2003 with the variety Scarlett. The latter can be attributed to “typical” malting barley varieties. Experimental plots were fertilised with different rates of ammonium nitrate (0, 30, 60, 90 and 120 kg ha-1 of N) before sowing. In the first series of experiments (1996-1999) fungicides were not used, and in the second series (2000-2003) spring barley was sprayed with triazole fungicides representing conventional practices in Lithuania for malting barley. Each year a treatment with or without fungicide application was added in order to evaluate the efficacy of fungicide application at a nitrogen rate of N90.

Disease severity (infected leaf area in %) was recorded on the top two leaves for fifteen primary tillers for each replicate plots at the early to medium milky ripe stage (BBCH 73-75).

A randomized block design with 3 replications was used. Means were compared using LSD test (P<0.05).

For the purpose of this study experimental years were grouped according to moisture regime during all growing seasons of spring barley. The growing seasons in 1996, 1997, 1998, 2000, 2001 and 2003 were attributed to normal and in 1999 and 2002 to dry.

Results

Barley crops in all experimental years were affected by several diseases, but in some years in very small amounts which individually were not considered damaging. During 1996-1998, under normal conditions for spring barley growth, conditions for leaf spot diseases such as net blotch (Pyrenophora teres), spot blotch (Cochliobolus sativus) and septoria leaf blotch (Septoria spp.) development were favourable (Table 1). The diseases began to spread more rapidly at the end of heading or beginning of water ripe. Leaf spot diseases in 1996-1998 significantly reduced grain yield. In 2000-2001 in the stands of spring barley Scarlett leaf spot diseases began to spread quite late, in the middle of milk development, therefore the diseases did not have any significant negative effect on grain yield. Under the dry conditions in 1999 and 2002 development of diseases was low and made no significant effect on grain yield. In 2003 diseases began to spread more intensively at the beginning of milk development (BBCH 73) (the data is shown in Table 1). Despite late attack, development of diseases was very intensive and at the end of milk development (BBCH 77) they destroyed almost all leaves in fungicide- untreated plots. However, in fungicide-treated plots two top leaves survived, and it resulted in a very marked yield increase.

Table 1: Severity of diseases in spring barley (variety Alsa in 1996-1999 and Scarlett in 2000-2003) and fungicide effect on the yield.

*significantly higher than untreated (P<0.05);

In dry 1999 and 2002, grain yield level was much lower and protein content in grain was much higher than in the years with more favourable moisture regime (Table 2). Under the dry conditions spring barley formed much lower grain number per area unit, while the grain was relatively large. Protein content in grain in dry years in all treatments was above the limit acceptable for malting barley. Considering these findings, growers of malting barley must take appropriate marketing measures instead of technological to reduce negative effect on income in dry years.

The positive effect of nitrogen fertilisers on grain yield was significant in all years with a rather similar shape of the nitrogen response curves. However, optimum rates of nitrogen calculated from these curves were different in two barley varieties and different years. Nitrogen fertilisers had a major effect on the number of grains per area, and especially on the number of ears per area unit. This effect was much higher under normal moisture conditions, than under dry. Nitrogen fertilisers had a rather limited effect on grain weight, but increased protein content in grain.

Table 2: Effect of nitrogen fertiliser rate on barley grain yield (t ha-1) and grain protein content (%) in normal and dry growing seasons

Conclusion

The yield of spring barley was significanty enhanced by the use of fungicides when leaf spot diseases started to spread at the beginning of grain filling. In the case of late, but very severe attack of diseases at the end of grain filling, the use of fungicides also resulted in a significantly higher yield. A low pressure of leaf spot diseases at milk development did not have any significant effect on yield. During the dry growing season the yield of spring barley was not significantly affected by the use of fungicides.

In dry 1999 and 2002, grain yield level was much lower and protein content in grain was much higher, than in the years with more favourable moisture regime. The positive effect of nitrogen fertilisers on grain yield and protein content in grain was significant almost in all cases. The shape of the nitrogen response curves was rather similar, but resulted in different optimum for nitrogen.

References

Toubia-Rahme H., Steffenson B. J. Sources of Resistance to Septoria passerini in Hordeum Vulgare and H. vulgare subs. spontaneum // Septoria and Stagonospora Diseases of Cereals. 1999, p. 156-158

Birch C.J., Fukai S., Broad I.J. Estimation of responses of yield and grain protein concentration of malting barley to nitrogen fertiliser using plant nitrogen uptake//Australian Journal of Agricultural Research.-1997,Vol.48.p.635-648.

Adresa autora