THE EFFECT OF REGENERATION TECHNOLOGY OF SWARD AND NITROGEN FERTILISATION ON YIELDING OF POSTBOGGY MEADOW

Mariusz Kulik, Ryszard Baryła, Dariusz Ciesielski
Department of Grassland and Landscape Forming, Faculty of Agrobioengineering, University of Life Sciences in Lublin, Poland

ABSTRACT

The studies were carried out in 2003–2006 in Didactic-Research Station in Sosnowica (East Poland) on peat-muck soil (Mt II). The meadow is located in a complex drained and reclaimed for agriculture in 1964–1966, situated in the middle reaches of the Piwonia river. Various meadow sward regeneration technologies and four levels of nitrogen fertilisation were used in experiment. The meadow subjected to overseeding and overseeding preceded by rototilling as well as by mechanical tillage had the significantly highest total dry matter yield in the four-year study period (2003–2006) while the meadow subjected to chemical tillage had the significantly lowest yield. The significantly lowest dry matter yield was obtained in the meadow not subjected to nitrogen fertilisation while the significantly highest for 180 and 120 kg ha^-1 dose of nitrogen. The plant species seeded in mixes had the highest yield in the meadow sward after the application of mechanical tillage and chemical tillage. The highest yields were recorded for the species Lolium perenne and Festulolium braunii, while the lowest for Trifolium pratense and Phleum pratense.

Key words: D.M. yield, overseeding, species, tillage.

INTRODUCTION

In modern times, meadow communities undergo continuous changes under the influence of human activity and changing soil and climate conditions. The lack of use or inadequate maintenance measures cause the degradation of meadow habitats manifested in the disappearance of valuable grasses and legumes from the sward and appearance of species of low value, mainly weeds. Degradation occurs more often in postboggy meadows due to the less stable habitat conditions. This process is manifested mainly in unfavourable floristic composition and poor fodder quality as well as considerable reduction of the production potential. In Poland, the mean annual dry matter yield from meadows is about 5 Mg ha^-1 while more than 50% of grasslands are neglected or degraded [22]. Fertilisation, particularly with nitrogen, is one of the ways of renovating degraded grasslands and increasing yields. The production efficiency of nitrogen has a very broad range and depends primarily on the level of fertilisation, species composition of the sward and habitat conditions, particularly soil type. In the case of organic soils, the vegetation of grass communities absorbs nitrogen from the soil; nitrogen is available as a result of the mineralisation of organic matter [1, 32]. Along with an increased level of nitrogen fertilisation, the dry matter yield from grasslands increases [2, 26] but in the case of very high doses of fertilizer, fertilisation is less cost-effective and becomes a hazard to the natural environment [12]. Grasslands that have been degraded to a larger extent should be renovated by means of overseeding or new seeding. Modern reseeding carried out by means of specialist seed drills ensures a greater efficiency of meadow and pasture renovation [4, 6, 11, 16, 23].

The aim of the study was to evaluate the effect of regeneration technology of sward and nitrogen fertilisation on yielding of postboggy meadow as well as chosen species and group of plants.

MATERIALS AND METHODS

The studies were carried out in 2003–2006 in Didactic-Research Station in Sosnowica (East Poland – 51˚31΄52˝ N; 23˚04΄33˝ E) on peat-muck soil (Mt II) formed of sedges and reed beds peat. The soil had an acidic pH (4.98 in 1n KCl), medium phosphorus content (35.2 mg) as well as low potassium (19.8 mg) and magnesium content (7.8 mg 100 g^-1 soil). The meadow is located in a complex drained and reclaimed for agriculture in 1964–1966, situated in the middle reaches of the Piwonia river. Various meadow sward regeneration technologies (Tab. 1) and four levels of nitrogen fertilisation (0; 60; 120 and 180 kg ha^-1) were used in mixed-design ANOVA experiment with 4 repetitions. Sward regeneration technologies was the main-plot factor while the nitrogen fertilisation – sub-plot one. In the years 2004–2006, nitrogen (in ammonium nitrate form) was applied in 3 equal doses in the spring and after the harvesting of the 1st and 2nd regrowth, while in 2003, in 2 doses after the harvesting of the 1st and 2nd regrowth. Every year in the spring, constant phosphorus (in monocalcium phosphate form) and potassium (in sylvinite form) fertilisation was used: P – 44 and K – 51 kg ha^-1. Before the experiment was established, Poa pratensis and dicotyledons predominated in the meadow sward [3]. Seed mixture with the following species composition was used in overseeding (23 kg ha^-1) or full seeding (38 kg ha^-1): Phleum pratense (cultivar Obra) – 30%, Festulolium braunii (cv. Felopa) – 25%, Lolium perenne (cv. Solen and Anna by 12,5%) – 25%, Dactylis glomerata (cv. Berta) – 10% and Trifolium pratense (cv. Raba and Rozeta by 5%) – 10%. The seeding was performed with a specialist seeding machine Hassia with fluted blades. The sward was cut 3 times at optimum dates for such communities. The area of the individual plots was 14 m². Before each regrowth, the yield was assessed by means of cutting the sward in a portion of the plot (7.7 m²) and average samples of green matter were collected in order to determine the absolute dry matter yield (vegetation samples were dried at 105ºC). The yield of the following species and groups of plants is presented in this paper: 1. Phleum pratense, 2. Festulolium braunii, 3. Lolium perenne, 4. Dactylis glomerata, 5. Trifolium pratense, 6. other grasses, 7. herbs and weeds. Holcus lanatus, Phalaris arundinacea and Alopecurus pratensis predominated in the group of other grasses while Polygonum persicaria, Cardaminopsis arenosa and Capsella bursa-pastoris predominated in the group of herbs and weeds. The yield of the above-mentioned species and groups of plants was calculated based on the total yield and percentage share in meadow sward determined by means of botanical-weight analysis. The results of the total dry matter yield and the yields of the particular species and groups of plants were analysed statistically using the analysis of variance method followed by Tukey’s range test.

To estimate the climate conditions in the years 2003–2006 type of growing season based on Relative Precipitation Index according to Kaczorowska [18] and Selyaninov hydrothermal coefficient [29] were calculated. The precipitation volume in the growing season in 2003–2005 was low while in 2006 it was high, which reflected the values of the hydrothermal index. The groundwater level was high in the spring (April–May) and was decreasing systematically in the following months (Fig. 1, Tab. 2). Such humidity conditions of the soil in the summer period considerably reduced the effectiveness of the agro-technical measures determining the yield and species composition of the meadow sward.

RESULTS

After analysing the mean total dry matter yield of meadow sward in the four-year study period (2003–2006), depending on the regeneration technology, the significantly lowest dry matter yield was obtained in the meadow subjected to chemical tillage (object 6) while the highest yield occurred in the meadow subjected to overseeding (object 4) and overseeding preceded by rototilling (object 5) as well as mechanical tillage (object 1). A meadow subjected to overseeding had the significantly highest dry matter yield in every study year except 2003 (Tab. 3). In that year, the significantly lowest yield was obtained after repeated rototilling and full seeding (object 8) and the highest yield occurred in a meadow subjected to rototilling and overseeding (object 5) as well as one subjected to chemical tillage, rototilling and full seeding (object 7). It should be noted that the yields in the first two years following mechanical tillage were lower while in the two following years they were significantly the highest (Tab. 3). The highest yields were recorded in 2004 (7.89–10.72 Mg ha^-1) and the lowest in 2003 (3.80–6.33 Mg ha^-1).

An analysis of the yields from the particular sward regrowths indicated considerable variation depending on the measures used. As regards the mean yields in the 2003–2006 period, the significantly highest dry matter yield from the first regrowth was recorded in the meadow subjected to mechanical tillage (object 1), while from the second and third regrowth – in the meadow subjected to overseeding (object 4). The highest mean dry matter yield in the four-year study period was obtained from the first regrowth (3.05–4.17 Mg ha^-1), and the lowest – from the third regrowth (0.97–1.39 Mg ha^-1).

As regards the mean total dry matter yields of meadow sward depending on nitrogen fertilisation, the significantly lowest dry matter yield was obtained in the meadow not subjected to nitrogen fertilisation (6.95 Mg ha^-1) while the highest yield occurred in the meadow (7.95 Mg ha^-1) subjected to fertilisation with a 180 kg ha^-1 dose of nitrogen (Tab. 4). However, the yields did not vary significantly in comparison with fertilisation at 120 kg ha^-1. The yielding of meadow sward in the individual years significantly depended on the level of nitrogen fertilisation except for 2004 when no significant differences were observed. It should be noted that very unfavourable weather conditions occurred in the study period: the years 2003–2005 were dry or very dry while 2006 was wet (Tab. 2).

The mean yield (2003–2006) of all the seeded species mixes (Phleum pratense, Festulolium braunii, Lolium perenne, Dactylis glomerata, Trifolium pratense) was significantly the highest after using intensive measures: seeding preceded by mechanical tillage (4.03 Mg ha^-1) as well as by chemical tillage and rototilling (3.96 Mg ha^-1); it was significantly the lowest (excluding the old sward) after overseeding (1.11 Mg ha^-1) without other measures (Tab. 5). The mean yields of the individual species in the four-year study period varied significantly as well. The dry matter yield of the seeded species increased with the intensity of the meadow sward regeneration measures used. After mechanical tillage, the significantly highest mean yield in the years 2003–2006 was obtained for Lolium perenne, while the significantly lowest – for Trifolium pratense. Another group was comprised by herbs and weeds that had the highest yields (3.26 Mg ha^-1) in comparison with other species in the year the experiment was established (Fig. 2). Polygonum persicaria, Cardaminopsis arenosa and Capsella bursa-pastoris predominated in that group. Poa pratensis had the significantly highest yield in the old sward (object 2). The highest yield for this species was recorded in 2004 (Fig. 2). Other grasses, among which Holcus lanatus, Phalaris arundinacea and Alopecurus pratensis prevailed, also had a high dry matter yield. After spraying with a defoliant and overseeding (object 3), the significantly highest yield in the meadow sward was recorded for Poa pratensis. The mean yield of other grass species was 2.54 Mg ha^-1. It should be noted that Lolium perenne had a high dry matter yield (2.28 Mg ha^-1) in 2004. The same relationships were observed in the meadow sward after using shallow rototilling and overseeding (object 5) where the significantly highest mean yield was recorded for P. pratensis. L. perenne and other grasses had significantly higher yields than the other species, except P. pratensis (Fig. 2). In the meadow sward subjected to overseeding (object 4), the significantly highest yield was recorded for P. pratensis. The yield of other grasses was 1.41 Mg ha^-1 while the yield of L. perenne was 0.69 Mg ha^-1. The meadow subjected to chemical tillage and seeding (object 6) had the significantly highest mean yield of L. perenne in the years 2003–2006 in comparison with other plant species and groups (Fig. 2). However, a significant variation of yields of the plant species and groups was observed in the particular study years. In 2003, the significantly highest yield was observed for the herb and weed group (1.97 Mg ha^-1), in 2004 – L. perenne (3.95 Mg ha^-1) while in 2006 – P. pratensis (3.37 Mg ha^-1). The same relationships occurred in the meadow sward subjected to chemical tillage, shallow rototilling and seeding (object 7). The meadow subjected to repeated rototilling and seeding was characterised by the significantly highest yield of P. pratensis in the 2003–2006 period (mean 2.18 Mg ha^-1) as well as in 2005 and 2006. In the first year, the significantly highest yield was observed for herbs and weeds, and in 2004 – for L. perenne (Fig. 2).

Regardless of the meadow sward regeneration measures used, the highest yield among the seeded species was recorded for Lolium perenne (0.69–2.07 Mg ha^-1), followed by Festulolium braunii (0.21–1.18 Mg ha^-1), Dactylis glomerata (0.09–0.52 Mg ha^-1), Trifolium pratense (0.02–0.48 Mg ha^-1) and Phleum pratense (0.10–0.30 Mg ha^-1).

DISCUSSION

The basic goal of regenerating degraded meadow sward is to improve its species composition and yielding. The regeneration can be carried out by direct seeding of grass and legumes plant seeds into old sward (overseeding method) or by full seeding (conducted after the chemical and mechanical tillage of old sward). The use of the regeneration methods above depends on the species composition of old sward, the degree of its degradation, humidity conditions and soil type [3]. In recent years, more and more often the overseeding method is used in agricultural research and practice because of the low costs (limited number of agro-technical measures, lower seeding rate) and possibility of seeding in old sward with specialist seed drills [3, 11]. Furthermore, old sward frequently contains local ecotypes of grasses and legumes, adapted to the particular habitat conditions. It should be noted, that meadow subjected to chemical tillage (object 6 and 7) characterized by the best germination and plant development taking into account 3-week period of drought after seeding or reseeding measures.

The lowest dry matter yield was obtained in the meadow subjected to chemical tillage (object 6) while the highest yield occurred in the meadow subjected to overseeding (object 4), overseeding preceded by rototilling (object 5) and by mechanical tillage (object 1). The conclusion is that the significantly highest yields were obtained in the meadows subjected to intensive and less intensive sward regeneration measures. It should be noted that the method based on a total chemical and mechanical tillage of old sward followed by new seeding requires considerably greater outlays which are not always compensated by the results achieved [3, 23, 28]. Furthermore, mechanical tillage on peat-muck soil intensifies the mineralisation of organic matter, particularly during drought, and leads to the withering of the growing seedlings [13]. Tillage and reseeding of grassland can also increase the rate of phosphorus losses in run-off above rates [8]. It should be noted that unfavourable weather conditions occurred in the study period (Fig. 1, Tab. 2). The yields in the first two years following mechanical tillage were lower while in 2005–2006, they were significantly the highest. Obtaining positive results after using the above methods of regenerating degraded meadow sward, particularly overseeding, largely depends on habitat conditions, mainly soil humidity, which is determined by precipitation volume and distribution [15, 27, 31].

The habitat conditions prevailing in the growing seasons, particularly precipitation volume and distribution, and temperature, were very unfavourable. The year the experiment was established proved to be a significant factor as it influenced the germination and initial growth of the seeded plant species. Such conditions resulted in a low yield of the seeded species and a high yield of dicotyledons from the herb and weed group, particularly after the total chemical and mechanical tillage of old sward and full seeding. The poor turfness of the area is conducive to the growth of dicotyledons that propagate very quickly in grass communities in such conditions [12, 13].

The humidity conditions in the growing season in 2004 were more advantageous, particularly in the second half of the season, when an even distribution of precipitation was recorded, despite the low precipitation volume in relation to the water demand of the grass communities. Such conditions were particularly conducive to the growth and development of Lolium perenne and Festulolium braunii that had the highest yield among the seeded species. These two species rank among the most suitable for the regeneration of degraded grasslands on peat-muck soils [6, 33]. One of the lowest yield was recorded for Trifolium pratense but it should be noted that mineral fertilisation of grasslands reduces the nodulation capacity of leguminous species [9, 20]. Moreover, red clover characterized by small persistency, especially in acidic conditions. It should be noted, that there was 3-week period of drought after reseeding measures. The seeded species had the lowest yield in the meadow subjected to overseeding without spraying (object 4) where Poa pratensis, the basic species of the old sward, had the significantly highest yield (Fig. 2). One of the conditions for successful overseeding is the reduction of the competitiveness of the old sward by spraying [4, 14], which is confirmed by the higher yield of species seeded in the sward of object 3 and 5. The advantageous distribution of precipitation in 2004 contributed to the higher yields of the individual species and the total dry matter yields in comparison with the other study years (Tab. 3). In the subsequent years (2005–2006), the habitat conditions were less advantageous because the growing season in 2005 was very dry while in 2006 it was very wet, with an unfavourable distribution of precipitation: 22.6 mm in July and 262 mm in August (Fig. 1; Tab. 2). This led to the lower dry matter yields from the second and third regrowth and thus lower total yields (Tab. 3–4). The seeded species had lower yields while Poa pratensis, the local ecotype, had a higher yield (Fig. 2). Other grasses had high yields, especially Holcus lanatus which characterizes by early maturation of seeds. Natural self-seeding of grassland provides remarkable amounts of seeds depending on the floristic diversity of the vegetation and time of self-seeding [28]. Among the seeded species, the highest yield was recorded for Lolium perenne, particularly in the meadow subject to mechanical tillage (object 1) and chemical tillage (object 6 and 7). The results of other studies conducted in similar habitat conditions indicate the high suitability of L. perenne for the regeneration of grassland [5, 7, 21]. Other researches show that frequent overseeding of L. perenne can reduce domination of P. pratensis. Moreover, that treatment is useful for weed suppression; however, long-term effects are uncertain [10]. A low stability of species composition can be observed in postboggy habitats while Poa pratensis and dicotyledonous weeds predominate in the sward [3, 19].

The significantly lowest dry matter yield was obtained in the meadow not subjected to nitrogen fertilisation while the significantly highest yield occurred in a meadow subjected to fertilisation with a 180 kg ha^-1 dose of nitrogen; it should be noted that the difference between the lowest and highest yield was 1 Mg ha^-1. Fertilisation with a dose of 120 and 180 kg N ha^-1 did not lead to a significant variation of the yields, which can result from the unfavourable climatic and habitat conditions in the study period and the fact that the plants absorbed nitrogen generated by the mineralisation of the organic matter in the peat-muck soil [4, 24, 25]. The concentration of mineral forms of nitrogen in groundwater of peat-muck soil depends on type and land use. The highest concentration of nitrogen occurs in summer time [30]. Besides, high doses of nitrogen fertilisation in meadows are not justified from the economic and environmental perspective [11, 12].

After using intensive measures (chemical or mechanical tillage) for the renovation of meadow sward dominated by Poa pratensis, the meadow was characterised by the significantly highest yield of the seeded species, particularly Lolium perenne in 2004 and as an average for the entire study period (Fig. 2). After applying these measures in the year the experiment was established, the significantly highest yield was recorded for herbs and weeds. The extremely unfavourable temperature and humidity conditions in 2003 were the key reason for that. The low humidity of the soil limited the germination of the seeds and growth of young seedlings. Achieving satisfying results after using various measures for the regeneration of meadow sward is only possible under the optimum humidity conditions [15, 27]. To succeed in improving grasslands by overseeding, long-term planning and appropriate management adapted to the needs of the seedlings are also crucial [17].

CONCLUSION

The meadow subjected to overseeding and the meadow subjected to overseeding preceded by rototilling and by mechanical tillage had the significantly highest total dry matter yield in the four-year study period (2003–2006) while the meadow subjected to chemical tillage had the significantly lowest yield. The meadow subjected to overseeding had the significantly highest dry matter yield in every study year except 2003.

The significantly lowest dry matter yield was obtained in the meadow not subjected to nitrogen fertilisation while the significantly highest yield occurred in a meadow subjected to fertilisation with a 180 kg ha^-1 dose of nitrogen, without significant differences in comparison with a dose of 120 kg ha^-1, which confirms the unsuitability of high doses of nitrogen fertilisation.

The plant species seeded in mixes had the highest yield in the meadow sward after the application of mechanical tillage and chemical tillage. The dry matter yield of these species increased with the intensity of the meadow sward regeneration measures used. Within this group, the highest yields were recorded for the species Lolium perenne and Festulolium braunii that are used in meadow seed mixtures in Europe due to their durability, yielding and nutritional value.

Accepted for print: 3.10.2015

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