**6.1 Weeds**

284 Sustainable Growth and Applications in Renewable Energy Sources

Fig. 13. Experimental fields near Szarvas (Southeast Hungary) to find optimal fertilizer

nutrients was shown to be 1:1:1 or 3:2:2 to maximize biomass yield of energy grass.

The response of biomass production to nitrogen is relatively high, already 60 kg N/ha can double the dry biomass matter as can be seen in Fig. 14. Until this dose, increasing amounts of nitrogen contribute to increasing biomass production in a linear relationship. Higher doses than 60 kg/ha nitrogen by itself does not increase the biomass production further due to the lack of other major nutrients, such as potassium and phosphorus. Adding these to the experiment in different doses we have found that biomass production can be increased a further 50 % until it reaches 13 tons dry matter per hectare. The best ratio of the three major

management type (photo: Róbert W. Pál)

**Yields (dry material t/ha)**

respectively).

0:00:00

30:00:00

45:00:00

60:00:00

90:00:00

30:60:60

30:120:120

Fig. 14. Biomass yields from fertilizer study near Szarvas (solonec meadow soil)

45:60:60

45:120:120

Nitrogen played an important role in biomass production increasing biomass weight in any phenophases, while potassium and phosphorus were shown to be important only in the early phenophases (spring and flowering period and the beginning of the flowering time,

The maximum dry matter production of Szarvasi-1 energy grass crop was shown to be dependent on soil types and water supply. In our experiments 13 tons per hectare dry matter derived from solonec meadow soil, while in better soil conditions we got 20-25 tons dry matter per hectare. High and low levels of the average groundwater table can also decrease biomass

60:60:60

**Combination of fertilizers (N:P:K) used (kg)**

60:120:120

60:0:60

60:0:120

60:60:0

60:120:0

90:60:60

90:120:120

### **6.1.1 Weed composition of Szarvasi-1 fields**

Knowledge of weed assemblies is extremely important for an effective weed management in all arable cultures. Therefore introducing new crops to large scale cultivation requires comprehensive preliminary investigations. In this chapter the characteristic species composition as well as abundances of weeds on Szarvasi-1 energy grass fields were determined and were compared to other arable crop cultures. Weed-crop competition was also studied in different soil conditions. The analyses were made on the basis of 22 energy grass, 60 cereal, 60 row crop and 15 alfalfa plots that were 4x4 m in size. A detailed study on this topic was published by Pál & Csete (2008).

### **6.1.2 Relation of weed species composition in energy grass to other arable cultures**

Comparing the weed composition of energy grass fields to other cultures on landscape and field level in terms of an ordination diagram showed a distinctive separation from cereals and row crops (Fig. 15.). A partial overlapping was detected with alfalfa fields, suggesting a similar species composition to this perennial crop.

Fig. 15. Scatter diagram of the weed composition of different crops (eg = energy grass, a = alfalfa, rc = row crops, c = cereals) (PCoA, Jaccard similarity index)

Tall Wheatgrass Cultivar Szarvasi–1 (*Elymus elongatus* subsp. *ponticus* cv. Szarvasi–1)

**6.1.3 Temporal variation of weed cover and species number** 

a

**6.1.4 Competitive ability of energy grass on weeds** 

t/ha the value decreased to 20-25 % and to 2-5 % at 20 t/ha.

Total cover of weeds (%)

a

b

(Fig. 16.).

test)

production.

**6.2 Fungi** 

as a Potential Energy Crop for Semi-Arid Lands of Eastern Europe 287

Our results suggested that energy grass cultures are able to develop properly established, nearly weedless stands with an average crop cover that increased from 77.5 to 90% during a 4 year period. Furthermore, a quick leaf-litter accumulation was observed during this time reaching an average ground cover of leaf-litter of as much as 55 %. This can contribute to a significantly low weed cover. The average species number declined from 16.5 to 4.8 and the average ground cover decreased from 62.5 to 2 %. This dynamic process is depicted in an example from an experimental site from the South of Hungary on three different soil types

c

Fig. 16. Changes in total weed cover during three years on three different soil types. Different letters indicate significant differences at P < 0.05; (mean, standard deviation); (t-

d

Alfisol Alfisol-Mollisol Aquic Mollisol Soil type

The competitive ability of energy grass crop can be demonstrated using experimental plot data. A strong linear relationship was found between the biomass production and the logarithmic values of total weed cover suggesting a high competitive ability of the crop. With less then 10 t/ha of biomass dry yield the cover of weeds exceeded 50 %, while at 15

*Elymus elongatus* is a rare, native plant species in Hungary; therefore its agricultural production is much more favourable than other exotic biomass grasses (e.g. *Miscanthus* × *giganteus, Sorghum bicolor*). Since its stands require a certain weed control only in the year of establishment, chemical input into the environment decreases significantly compared to other intensive cultures. Under favourable conditions, energy grass can entirely close its canopy and exclude more weed species or considerably decrease their cover by the third year of cultivation. This remarkable competitive ability of a crop is appreciated by farmers as it decreases the demand of herbicide use as well as the costs of the agricultural

Studies on the pests of Szarvasi-1 energy grass are in progress in Hungary, but it is already clear that the plant is sensitive to many of the most common fungal infections typical for cereals. At our experimental sites the most important fungal infection was mildew (*Blumeria* 

e

<sup>d</sup> <sup>g</sup>

f

1st year 2nd year 3rd year

Regarding the life form distribution of the weeds in the different cultures, energy grass fields resembled annual crops the most, considering all life form categories. However, geophytes were more representative, while therophytes were less common. In alfalfa, a higher proportion of geophytes and hemicryptophytes were found, while therophytes were even more underrepresented than in energy grass fields. Considering the observed life form distribution of the characteristic weed community of each crop, energy grass took an intermediate position between annual crops and the perennial alfalfa.

The characteristic species composition of the different cultures is shown in Table 4. There was only one species (*Convolvulus arvensis*) which could be regarded as uniformly common in every culture. There were 12 species characterizing the cereals, six the row crops, two in case of alfalfa and only one (*Bromus japonicus*) in case of energy grass. *Bromus japonicus* as a problematic weed was already present from the first year of sowing, and despite its annual life form, it has been continuously present and infesting the fields. On the other hand, energy grass fields are often characterized by a lack or a decreased importance of several serious weed species which are quite dominant in other arable crops: *Amaranthus* spp*., Ambrosia artemisiifolia, Apera spica-venti, Artemisia vulgaris, Cirsium arvense, Echinochloa crusgalli,* and *Galium aparine*.


Table 4. Frequencies of the weed species in different crops

### **6.1.3 Temporal variation of weed cover and species number**

Our results suggested that energy grass cultures are able to develop properly established, nearly weedless stands with an average crop cover that increased from 77.5 to 90% during a 4 year period. Furthermore, a quick leaf-litter accumulation was observed during this time reaching an average ground cover of leaf-litter of as much as 55 %. This can contribute to a significantly low weed cover. The average species number declined from 16.5 to 4.8 and the average ground cover decreased from 62.5 to 2 %. This dynamic process is depicted in an example from an experimental site from the South of Hungary on three different soil types (Fig. 16.).

Fig. 16. Changes in total weed cover during three years on three different soil types. Different letters indicate significant differences at P < 0.05; (mean, standard deviation); (ttest)
