European Journal of Agronomy 12 2000 69–78 www.elsevier.comlocateeja
Effect of plant density and nitrogen rates upon the leaf area of seed sugar beet on seed yield and quality
M. Pospisˇil a,, A. Pospisˇil a, M. Rastija b
a Faculty of Agriculture, University of Zagreb, Department of Field Crops, Svetosˇimunska 25, 10000 Zagreb, Croatia b Faculty of Agriculture, University of J. J. Strossmayer, Trg sv. Trojstva 3, 31000 Osijek, Croatia
Accepted 14 September 1999
Abstract
Three-year field trials were set up on eutric brown soil in northwestern Croatia Zagreb with the objective to determine the effect of plant density and nitrogen rates on the formation and size of leaf area of seed sugar beet, and
on the yield and seed quality in seed production without transplanting. Investigations should also reveal how much the yield and quality of sugar beet seed depend on the leaf area index LAI . Four plant densities of seed sugar beet
were investigated after crop wintering 40 000, 80 000, 120 000, and 160 000 plantsha as well as three nitrogen rates 60, 120, and 180 kgha applied in two identical topdressings: at the beginning of the spring growing period and
immediately before shooting of inflorescence stalks. Leaf area formation was strongly influenced by weather conditions. An increase of plant density from 40 000 to 160 000 plantsha led to a decrease of leaf area per plant. Raised nitrogen
rates in topdressing caused an increase of leaf area, depending on the precipitation and soil fertility. Maximum LAI, achieved in the flowering stage, grew almost linearly with increasing plant density LAI: 1.77–4.85 m
2m2, but was statistically significant only up to 120 000 plantsha. Raised nitrogen rates in topdressing led to a significant increase
of the LAI in the stage of inflorescence stalk shooting, though not in full flowering. On the basis of this research, seed yield and germination of seed sugar beet could not be predicted regarding LAI in the flowering stage. © 2000
Elsevier Science B.V. All rights reserved.
Keywords: LAI; Leaf area per plant; Nitrogen rates; Plant density; Seed sugar beet
1. Introduction per unit area, as well as appropriate fertilization,
particularly with nitrogen, are central problems in the technological production process of all field
Research on the extent to which the plant crops and specially in sugar beet seed production.
density and nitrogen rates influence the growth A survey of the research results, available to us,
and formation of leaf area in particular develop- on this problem in the world and in this country
ment stages, especially those decisive for the yield did not reveal any published results on the effect
and quality of sugar beet seed, has major scientific of leaf area, or leaf area index LAI upon the
and production importance since it contributes to yield and quality of sugar beet. Various methods
a better seed utilization in final processing. It is have been applied to determine leaf area in sugar
thought that number and distribution of plants beet Campbell and Viets, 1967; Barbieri, 1983;
Fo¨rkel, 1985; Milford et al. 1985; Rover and
Corresponding author. Tel.: +385-1-239-3775;
Koch, 1995.
fax: +385-1-239-3703. E-mail address: mpospisilagr.hr M. Pospis
ˇil
Areas under seed sugar beet are small in com-
1161-030100 - see front matter © 2000 Elsevier Science B.V. All rights reserved. PII: S 1 1 6 1 -0 3 0 1 9 9 0 0 04 5 - 3
70 M. Pospisˇil et al. European Journal of Agronomy 12 2000 69–78
parison with areas under other field crops. This is split-plot method in five replications. Cultivar
OS-Nada, its mother 2n=18 and father 4n= the main reason why there are very few profes-
sional or
scientific studies
from this
area. 36 lines, were used as test crops. The ratio of
mother and father components at sowing was Researchers from North America Campbell,
1968, the UK and Denmark Scott, 1968; 6:0:2. Basic fertilization for seed sugar beet was
carried out with 50 kgha of N, 150 kgha of Longden and Scott, 1973; Longden, 1974 con-
ducted research with twice as many plants P
2 O
5 , and 300 kg ha of K
2 O. Sugar beet was
sown at the end of August at a between-row 300 000 plantsha at harvest as commonly
recommended in
other production
regions. spacing of 50 cm and within-row spacings of 11.4,
8.6, 7.1, and 5.7 cm. In spring, a density correction Trogisch 1985 maintains that a plant density of
150 000–250 000 plantsha at harvest is desirable was made according to the test treatments.
Leaf area per plant and the LAI were deter- for seed sugar beet grown under European condi-
tions. Under
the conditions
prevailing in
mined in characteristic pheno-stages of seed sugar beet at the start of vegetation in spring, in the
Vojvodina FR Yugoslavia, the highest yield and best seed quality of sugar beet were obtained with
stage of inflorescence stalk appearance and in full flowering using the punch method Campbell and
plant densities of 130 000 to 150 000 plantsha after wintering Stefanovic´, 1987. Based on the trial
Viets, 1967. In the said stages, measurements were made on ten plants from each treatment and
results achieved in eastern Slavonija Croatia, Kristek and Matic´ 1984 concluded that good
involved the number of leaves, the leaf weight per plant and their dry matter. Leaves with blades
yields might be obtained with 65 000–80 000 plantsha at harvest. According to the authors,
longer than 2 cm were counted. All observations and measurements in the trial were carried out on
nitrogen rates applied with topdressing to direct- drilled seed sugar beet vary, depending on the soil,
mother plants. Seed sugar beet was harvested at the end of July. Seed yield and quality were
from 150 to 250 kgha Longden and Johnson, 1977; Zarisˇnajak and Sˇijan, 1991; Rastija, 1993.
determined after the harvest. The data obtained were processed by up-to-date statistical methods
The objective of this research is to determine the effect of plant density and nitrogen application
analysis of variance, correlation applying com- puter programs Microsoft Excel 5.0 and Mstat.
upon the formation and size of leaf area, LAI, yield and quality of sugar beet seed. Investigations
Analyses of weather conditions during three growing seasons showed considerable variation in
should also reveal how much the yield and quality of sugar beet seed depend on the LAI.
precipitation distribution from year to year Fig. 1. Particularly unfavourable precipitation
distribution was recorded in 1991–92. Water balance after Thornhwaite’s method indicates a
2. Material and method
