Effects of vegetation space, determined by the planting pattern (continuous row and 20-cm intra-row spacing), on peppermint productive traits were studied. Although, the increase of leaf number per area unit was great in both variants in the second year, effects of vegetation space on productive properties were not significant.

Key words: peppermint, vegetation space, productive traits.

Peppermint planting can be performed in 50-90 cm inter-row spacing (Morton and Leonard, 1967, Hornok, 1990, Kišgeci and Adamović, 1994, Dražić, 1998, Dražić et al., 1998), with or without intra-row spacing (Adamović et al., 1982).

In our country, peppermint is usually planted in 60-70-cm inter-row spacing (Stepanović, 1983, 1998) without intra-row spacing.

The aim of this study was to observe effects of vegetation space on yield and quality of peppermint during the first and the second year of cultivation.

The trial with peppermint Mitcham was set up in the experimental field of the Institute in Pančevo in 1998 and 1999 in the following two variants:

-continuous row;
-20-cm intra-row spacing.

The two-factorial trial was set up according to a randomised complete block design with four replications. The elementary plot size amounted to 15 m². The 70-cm inter-row spacing was permanent. Planting was done in October, while the first and second cutting were performed in the third decade of July, i.e. the first decade of October, respectively.

The following properties were analysed in the present study: plant height, stem and leaf number, herb, leaf and essential oil yield, as well as, harvest index. Means () and coefficient of variance (CV) were esteemed. The obtained results were statistically processed by the two-factorial analysis of variance, while significance was evaluated by the F and LSD tests (Hadživuković, 1973).

Conditions under which the trial was conducted. Pančevo is located under conditions of semi-arid climate. Soil of the experimental plot is classified into marshy black soils. The average annual air temperature amounts to 11.3^oC, while the average air temperature of the growing period (April-September) amounts to 18.2^oC. The average vegetation and annual precipitation amount to 380 mm and 664 mm, respectively.

Highly statistically significant differences for the leaf number and harvest index between the years were determined by the two factorial analysis of variance. Moreover, the leaf number was significantly affected by the planting pattern. Year x planting pattern interaction was expressed only in the harvest index (Table 1).

Morphological traits. - Plant growth and the stem number per area unit were approximately equal for both variants in the investigation years, what is in accordance with the literature data (Adamović et al., 1982). A somewhat greater variation in the stem number was expressed in the 20-cm intra-row spacing during the first year.

Traits	1998				1999
	Continuous row		70 x 20 cm		Continuous row		70 x 20 cm
		CV		CV		CV		CV
Height, cm	54	9.6	48	5.3	50	9.4	54	9
Stem number m-2	51	10.2	43	19	56	9.6	57	13
Leaf number m-2	1.464xx	21	1.067	6.8	2.250xx	6.7	2.150xx	3.6

The leaf number per area unit was reliably higher in continuous row planting than planting in the 20-cm intra-row spacing during the first year. During the second year, the leaf number was significantly increased in both variants. This increase amounted to 50-65%, while the leaf number variation was lower.

Productive traits. - Herb yield obtained with planting in 70-cm inter-row spacing in the first year was higher (by 8.5%) than in planting in 20-cm intra-row spacing. These results are in accordance with results obtained by Adamović et al. (1982). Yield during the second year was decreased (by 9%) in planting in continuous rows.

Traits	1998				1999
	Continuous row		70 x 20 cm		Continuous row		70 x 20 cm
		CV		CV		CV		CV
Herb yield (kg ha-1)	1.607	13.4	1.482	16.6	1.444	17.6	1.581	9.1
Leaf yield (kg ha-1)	982	5.2	840	16.7	793	10.5	845	8.7
Essential oil yield (kg ha-1)	29.6	13.7	25.1	15.7	25.3	2.4	30.2	3.2
Harvest index (Hi)	0.60	4.8	0.64xx	8.4	0.57	2.8	0.57	6.7

Peppermint leaf yield was similar to herb yield. Higher yield was achieved by planting in continuous rows, i.e. 20-cm intra-row spacing, during the first, i.e. second year, respectively. Obtained differences in leaf and herb yields were not significant.

The highest essential oil yield was obtained in variants and years with higher herb and leaf yields. These results confirm the positive correlation between vegetative mass yield and essential oil yield as also stated by Adamović et al. 1982; Stepanović and Milojević, 1988; Dražić 1998; Dražić et al., 1998.

The highest value of the relation between economic and biological yield was detected in planting pattern of 20-cm intra-row spacing during the first year. The values of the harvest index were equal in the second year, but lower than in the first year. These differences can be caused by the interaction between years and planting patterns.

The investigation of effects of vegetation space on productive traits shows that there were no differences between variants pertaining to plant growth and the stem number per area unit. The leaf number, as an important yield component, was significantly higher for both variants in the second year.

Differences in herb, leaf and essential oil yields were not statistically significant. Differences in the harvest index values can be caused even by the interaction between year and planting pattern that determined the size of vegetation space.

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