3. Material and Methods

3.1. Field research station Berge - location, soil and weather conditions

▼ 19 (continued)

Berge research station, belonging to the Institute of Crop Science, Faculty of Agriculture and Horticulture (Humboldt-University) is located in Brandenburg area, about 40 km north-west of Berlin. It lies towards the north, west and south rolling Nauener plane on a geographical latitude of 52°37’N, longitude of 12°47’E and altitude NN 40 m. Soil type is Orthic Luvisols, gray brown podzolic soils. Soil texture is loamy sand to sandy loam (top), sand to sandy loam (below). Table 1 shows soil texture and table 2 chemical composition upto 50 cm of soil depth.

▼ 20 

Table 1: Soil texture at Berge research station (Köhn 2002)

Depth

[cm]

Coarse

Sand

Medium

Sand

Fine

Sand

Coarse

Schluff

Medium

Schluff

Fine

Schluff

Clay

0-20

4.1

30.1

41.4

8.4

4.7

3.5

7.8

30-50

3.8

28.7

41.6

8.8

4.5

3.8

8.8

Table 2: Soil chemical composition at Berge research station (Köhn 2002)

Depth

[cm]

Organic matter

P

K

Mg

Cu

Mn

Zn

pH

 

%

mg 100 g -1 soil

ppm

 

0-20

1.4

22.9

14.5

6.3

4.8

78.0

5.8

6.1

30-50

1.3

19.2

20.4

9.0

4.1

52.3

4.8

6.8

Rainfall and air temperature means recorded over a period of 30 years (between 1971 and 2000) are indicated in table 3. The mean air temperature for the years from 1971 to 2000 was 9.3 °C, while the rainfall mean over the same period of time was 502 mm.

▼ 21 

Table 3: Temperature and rainfall means between 1971 and 2000, Berge (Köhn 2002)

Month

Mean daily temperature [°C]

Rainfall

[mm]

Month

Mean daily temperature [°C]

Rainfall

[mm]

January

0.7

35.0

July

18.6

46.8

February

1.1

28.5

August

18.2

54.1

March

4.3

35.9

September

13.9

41.3

April

8.3

30.9

October

9.3

31.9

May

13.8

47.5

November

4.4

37.2

June

16.7

65.6

December

1.8

47.2

Daily weather focus was monitored from the meteorological station located within the experimental field [temperature (°C), rainfall (mm) and other parameters]. Mean monthly air temperature and rainfall distribution for each experimental year of 2002 and 2003 were calculated.

Climatic conditions of the research station over the period between 1971 and 2000 were also compiled (in this experiment only mean monthly temperatures and rainfall were considered).

▼ 22 

In year 2002 over 737 mm precipitation was recorded at the Research station of Berge, out of which 325 mm fell within the vegetation period. The average temperature within the same period was 17.6 °C. Year 2003 was characterised by low rainfall figures (342 mm), nearly half that of 2002. Approximately half of annual precipitation for each year was received during the vegetation period.

Figure 1: Mean monthly rainfall distribution (mm) and air temperature for experimental years 2002, 2003 and 2004

The figure 1 shows precipitation (mm) and corresponding mean air temperatures during the experimental years 2002 and 2003. As indicated comparing to the long-term averages, the year 2002 received the highest rainfall during the vegetation period. Rainfall over a period of 30 years (1971-2000) at the experimental site averaged 501.9 mm during 12 months and nearly 250 mm during the growing period from May to September. In the experimental year 2003, a severe water shortage was noted in the month of August which led to an earlier than usual harvest of the crops, especially of early varieties whose leaves dried out faster than those of mid-early maturity varieties. Long-term averages for air temperatures during the vegetation period were lower than in 2002 and 2003. Again highest mean air temperatures during the vegetation period were recorded in 2003, with the highest mean air temperature in the month of August (21.3 °C). However, there was no considerable deviation from long-term average temperatures in both experimental years 2002 and 2003.

3.2. Silage maize maturity groups used

▼ 23 

All the silage maize varieties used in the experimental years 2002, 2003 and 2004 including selected and recommended varieties fall under maturity groups as follows:

Early maturity group:S 180 - S 220

Mid-early maturity group:S 230 – S 250

▼ 24 

Mid-late maturity group: S 260 – S 280.

A difference of 10 in silage maturity number signifies a one percent point difference in dry matter content of the whole plant. Classification of maize genotypes by maturity group according to FAO number does not consider the differences in full maturity of rest of the plant. That results in yearly re-classification of some individual genotypes from one group to another (Wang 2001).

Table 4: Early and mid-early silage maize varieties at location Berge (check and core varieties 2002-2004)

Year

Early maturity group

Mid-early maturity group

 

Number

(varieties)

Check varieties

Number

(varieties)

Check varieties

2002

20

Tassilo

Symphony

Diplomat

Sagitta

22

Probat, Fjord

Romario, Eurostar

Effekt, Rivaldo

2003

18

Pernel, Tassilo,

Symphony, Ravenna

Talman, Early Star

Ambros, PR39G12

PR39P49

25

LG 3226, Rivaldo

Sandrina

Acapulco

Topper

Flavi

2004

16

Tassilo

Baxxos

Nescio

25

Rivaldo, LG 3226

Topper, Lacta

PR39B50, Pontos

Core varieties

3

Tassilo

Baxxos

Nescio

6

Lacta, LG 3226

Pontos, R39B50

Rivaldo, Topper

3.3. Measurements and observations

▼ 25 

Leaf area and leaf area index measurements were done once in a week throughout the vegetation periods. Leaf area index was obtained through manual measurements and the use of a LAI 2000 plant canopy analyser instrument. With the LAI 2000 other parameters like light interception and leaf mean tilt angle were also obtained. Both methods were deployed on the same dates of measurements, but not started on the same dates. Manual measurements were started on earlier stage of leaf development than LAI 2000 in both years. Plant height was also measured on the same dates including other observations like leaf number, total number of senesced leaves, number of nodes per plant, number of cobs per plant and cob leaf positions, mechanical damages by wind or heavy rain and infections by insects and pests. Intermediate harvest was conducted in 2002 to determine leaf area and leaf area index by the integration method. The results obtained were used in 2003 for varieties, which were tested in both years.

During the measurements of leaves (length and breadth), every leaf was labelled using a water resistant marker beginning with the lowest, marked 1, up to the top last fully expanded leaf. Only leaf lengths of the remaining, non-fully expanded leaves were measured. The next date of measurements proceeded with the previous, non-fully expanded leaves. This facilitated faster measurements as unnecessary repetitions of the already fully expanded leaves during previous measurements were avoided. The assumption made was that the leaves, which were considered fully expanded, increased no more in length or width after the last date of measurement. In 2003 only leaf lengths were measured, while in the previous year both leaf length and width were measured simultaneously in every date of measurement until full expansion. The results of leaf measurements of 2002 of the same varieties tested in both years were applied in 2003 in intergration to find the leaf factors of the same varieties.

Maturity groups of early and mid-early varieties of forage maize were used (tables A1-A5). The genotypes were planted as sub-plots in a randomised complete block design with four replications (Figure A1-A4). Planting was done on 30.04.2002 and 29.04.2003. Each plot consisted of 4 rows, 10 metres long and 3 metres wide.

▼ 26 

Measurements, numbering, observations and data collections made during the vegetation period included:

Measurement of plant height (cm)

Number of nodes

▼ 27 

Leaf area of individual leaves (length * breath)* factor

Number of cobs per plant

Location of the cob-leaf on the plant

▼ 28 

Number of withered (dead) leaves per plant: counting of dry (withered) leaves was done on every date of measurements starting from the first leaf generation, moving upwards. Leaf senescence from the top downwards was also noted as the plants approached maturity. Rates of individual leaf senescence were also approximated through visual observations as a fraction of the green part of the leaf (3/4, 1/2, 1/3 and 1/4).

Total number of leaves per plant (leaf generation): was considered the number of leaves from the first leaf that appeared after germination to the last top most leaf of the plant.

Breakage

▼ 29 

Insect infections

Measurement of LAI with the Plant Canopy Analyser LAI 2000: This instrument measured and computed a combination of parameters including leaf area index (LAI), leaf angle and light interception.

Two methods were used to determine leaf area and leaf area index of the varieties.

3.3.1. Manual method of measuring LA and LAI

▼ 30 

Using a meter stick, the length and breadth of each leaf of the tagged plants were measured from the first leaf generation upwards. Leaf length was considered as the length from a leaf base to leaf tip, leaf breadth as the breadth of the widest portion of the leaf blade (cm). Further measurements were stopped after the leaf had attained full expansion indicated by the exposure of the leaf base. The leaf area of every individual leaf was determined by multiplying length and breadth and a factor of a given leaf.

Leaf area was determined using the formula:

LA = length * breadth * factor b1 [Eq. 5].

▼ 31 

Factor b1 is a coefficient depending on the individual leaf and its development (according to Kvet et al. 1971, Hatfield et al.1976). Factor b1 lies between 0.65 and 0.80. In year 2002 and partly in 2003, specified plants in the inner row of each plot were harvested in mid July (the time when maximum leaf areas for all the varieties were attained). All existing green leaves were removed from the stock arranged on tables in ascending order from the lowest leaf to the last (in order of leaf generation). Beginning with the lowest leaf each leaf was folded into 1/2, 1/4 and 1/8 segments (a total of 5 segments per leaf were obtained). Widths of these segments were measured, including width of leaf base. The full length of each leaf was measured. Using integration method, the leaf factor was calculated for individual leaf generation. With the three parameters: leaf length, leaf width and leaf factor known, leaf area of each individual leaf was calculated as a product of the three parameters. Leaf factor results of the varieties tested in 2002 were used in the calculation of leaf area of these same varieties, which were tested in 2003. The procedure of finding leaf factor was repeated only on the newly introduced varieties in 2003. This was also partly due to the time consuming labour intensive nature of the procedure. The leaf area index of every plot was the product of the sum of all individual leaves of a plant and the plant density divided by the total area occupied by the plants.

3.3.2. Plant canopy analyser LAI 2000 method of measuring LAI

Using LAI-2000 five measurements were made, within the row adjacent to the marked plant. The first measurement was taken above the plant canopy the other four were taken below the plant canopy diagonally across the rows. The first one was taken in the row, the second ¼ of the way a cross, the third in the middle and the fourth ¾ of the way across the row. Measurements were taken in the early morning hours of the day (8°° - 11°°) to avoid the effect of direct sun- rays and also under obscured cloudy conditions, whereby the contribution of scattered radiation is low. Some measurements were also done in the late evening hours on clear days (from 16°° until 18°°), where direct sunrays or drizzles. View caps were used to block undesired objects from the sensors view, such as the operator, a neighbouring plot and portion of the sky, which contains the sun. Under critical conditions of intermittent rainfall or open sky, direct sun-ray, which could affect the results, only two replications per maturity group were measured. However this method was not used simultaneously at the start of manual measurement (was used from 23.07.02, when most of the plant leaves were already fully opened and from 18.06.03). LAI calculations using this method assume that the below-canopy readings do not include radiation that was reflected or transmitted by foliage, the foliage elements are small compared to the area of view of each ring. Since the optical sensor has a broad field-of-view, the size of the canopy or plot is an important consideration. If the plot is too small, the sensor’s field-of-view will extend beyond the edge of the foliage being measured and LAI will be underestimated (or overestimated, if the plot is surrounded by denser foliage), the distribution of foliage elements is random, the foliage is azimuthly randomly orientated, that is, it does not matter how the foliage is inclined, but the leaves should be facing all compass directions (Daughtry & Hollinger 1984).

3.4. Growing Degree Days (GDD)

Using the formula according to AGPM (L’Association Générale des Producteurs de Maïs):

▼ 32 

[Eq. 6]

Whereby:

T1:sowing to flowering

▼ 33 

T2:Flowering to silage maturity

Tmax:maximum daily temperature

Tmin:minimum daily temperature

▼ 34 

Tb:base temperature (8°C)

When [(Tmax + Tmin)/ 2] < 8, that day was not counted (ignored) and when Tmax > 30, Tmax was taken as 30, temperature sum were calculated for the entire vegetative period. Through this method, dates and particular phases of development with their corresponding temperature sum could be found.

3.5. Data analysis

Analysis of variance and evaluation of the 10-years research series were carried out using EFDAS 1 and 2 Programme (Bundessortenamt 1993a, b). Forage quality was analysed using Near-Infrared Reflectance Spectroscopy (NIRS) method carried out at the Regional department for consumer protection and agriculture at Paulinenaue. Analysis were conducted for both years and pooled together. F values for treatment effects and their interactions were considered significant at the P < 0.05. However due to various reactions of the trials and different environmental conditions (soil and weather), any significant effect on the trials (variety) can be interpreted for each year separately (Bätz 1984). Yield and quality analysis of silage maize was done through separate harvesting of cob (including cobleaf) and residual plant components (stems and leaves) from the inner rows of the plots. From the probes dry matter contents were calculated.

▼ 35 

NIRS analysis of forage quality: Whole plant probes were taken to the department of grassland and fodder production, consumer protection and agriculture. Starch content, crude protein, crude fibre as well as contents of enzyme-soluble organic substances were analysed. Out of these results, energy content was estimated using the estimation formula according to Weißbach et al. (1996 a, b).


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