PRODUCTIVITY AND COEXISTENCE OF WHITE CLOVER AND GRASSES GROWN IN BINARY MIXTURES - A. Adamovich

Latvia University of Agriculture, 2 Liela Street, LV-3001, Jelgava, Latvia

SUMMARY

In long-term field trials the productivity, coexistence, persistency and dynamics of crude protein (CP) content of white clover grown in binary clover/grass swards in mixtures with 13 grass species was studied on brown-lessive and sod-podzolic gleysolic soils of Latvia. The ratio of white clover to grass in mixture was 1:1. The utilization of a sward was three and five cuttings. Crude protein content in dry matter (DM) was determined between cuttings both for each two-component clover/grass sward and for each component in a sward. Experiments have shown that the productivity of white clover/grass and survival of white clover in a sward were greatly due to cenotic activity of grasses. The inclusion of Poa pratensis, Lolium perenne, Agrostis stolonifera, Festuca rubra, Festuca pratensis, Phleum pratense in mixture favoured the persistency of white clover in binary clover/grass swards. Tall and cenotically active grasses such as Arrenatherum elatius, Bromus inermis, Dactylis glomerata, Festuca arundinacea reduced content and productive persistency of white clover in a sward. The content of white clover and interaction between clover and definite species in clover/grass sward determined crude protein content in total DM yield of each sward as well as CP content for each component in a sward.

Keywords: coexistence, productivity, white clover, grass mixtures

INTRODUCTION

Dairy farming is a major branch of agriculture in Latvia. Therefore, providing livestock with high quality grass forage over the whole grazing season is of great importance. However, the high quality grass forage should not be obtained at too high a cost. Perennial forage legume-grass stands correspond best to the required demands. Inclusion of white clover in legume-grass stands contributes to the production of high quality herbage swards. Longevity, winterhardiness, plasticity, persistence under multi-cut systems and resistance to treading by livestock, as well as good regrowth are the attributes that make white clover a most suitable component in pastures. The nutritive value of white clover depends on the favourable leaf: stem ratio in total crop herbage and in full flower is up to 65-70 and 15 percent, respectively [1, 5]. White clover-grass swards are successfully utilized when replacing the summer grazing by feeding green cut forages to livestock. Survival and persistence of white clover in a sward has become topical under multi-cut treatments, growing white clover in mixtures with grasses different by height, leafage, regrowth ability and other biological traits.

METHODS

The field trials were conducted on brown-lessive (pH_KCl was 6.7, mobile P-52, K-128 mg kg-¹ was 6.2, P-39, K-95 mg kg-¹ of soil) of soil) and sod-podzolic gleysolic (pH_KCl soils in 1990-1996. Binary seeds mixtures were composed of local 'Priekulu 61' white clover and thirteen grass species recommended for growing under the conditions in Latvia. The grass seeding rates in pure stands and in mixed fields were 10 million germinative seeds per ha. The seeding time for mixtures was early May 1990 and 1991. The fertilizer background. The utilization of a sward was three-cut was as follows: N 0, N 90 _{(45 + 45)}, P 40, K 150 kg ha-¹ treatments: the first and the second cuts at the bud stage of white clover, the third one, late September, and fivefold cutting at 15 to 20 cm stubble height. The botanical composition of a sward was determined both between growing stages and for each cut. The crude protein content was determined using the Kjeldahl procedure.

RESULTS AND DISCUSSION

The studies have shown that on both soil types white clover in binary mixtures with grasses develops productive forage grass swards with an average dry matter yield ranging from 6.78 to 6.98 t ha-¹ under three cut treatments in five years of sward utilization and 6.06 to 6.70 t ha-¹ under five cut treatments in the growing season receiving no fertilizer N (Tables 1 and 2). The applications of mineral fertilizer N increased the productivity of white clover-grass swards up to 7.16-7.78 and 7.45-8.75 t DM ha-¹, respectively. There was little DM advantage, extra 0.67 to 1.77 t ha-¹ with an input of 90 kg N ha-¹, splitting the fertilizer into two applications. The results agreed with the information of comparatively low efficiency of fertilizer N in mixed white clover-grass swards [1-7].

Early cauline-leaved grasses in combination with white clover produced average DM yields of 7.14 to 8.78 t ha-¹; medium early and late upper cauline-leaved grasses provided average DM yields ranging from 7.47 to 8.94 and 7.19 to 9.26 t ha-¹, respectively. In mixtures with companion bottom grasses, DM yields 5.94 to 8.45 t ha-¹ were obtained under five-cut treatments in a growing season. Three-cut treatments in a season resulted in DM yield increase by 0.28-0.98 t ha-¹. White clover in the presence of grasses with different growth patterns contributed to the continuous production of high quality fresh herbage which could be utilized for feeding to livestock, as well as for pasture.

The average CP yields of 16.7 to 23.4 percent in dry matter were obtained largely due to white clover content in the mixed sward. Our studies show that mixed white clover-grass swards provided CP yields of 1.25 to 1.75 and 1.14 to 1.63 t ha-¹ on brown-lessive and sod-podzolic gleysolic soils, respectively. In totality, the productivity of mixed white clover-grass stands, depending on the number of clipping treatments and fertilization, was by 0.20 to 1.30 t DM ha-¹ higher on brown-lessive soils compared to sod-podzolic gleysolic soils. This could be explained by better survival of white clover in mixed swards on brown-lessive soils. Depending on the phytocenotic activity of grasses, dynamics of white clover content in swards receiving no fertilizer N between the years of sward utilization under five-cut treatments was as follows: 36.7 to 45.2 and 44.7 to 55.2 percent in the first and second years, and 32.7 to 40.1 percent, 29.6 to 35.8 percent and 27.9 to 33.5 percent in the third, fourth and fifth years, respectively. Analogous changes were noted on sod-podzolic gleysolic soils. On these soils the coexistence of white clover and grasses in a sward was subjected to greater fluctuations, particularly during periods of drought. Splitting the mineral fertilizer 90 kg N ha-¹ into two applications (one after first and second cut) eliminated white clover ration in a sward by 6.4 to 9.7 percent average on sod-podzolic gleysolic soils. Three-cut treatments resulted in significant falls of white clover ratio in swards receiving no fertilizer N compared to five-cut treatments. Changes in white clover content in these swards between the years of sward utilization were as follows: 30.2 to 38.3 percent, 32.4 to 36.9 percent, 26.7 to 30.5 percent, 18.7 to 31.9 percent and 15.4 to 26.6 percent in the first, second, third, fourth and fifth years of sward utilization, respectively.

Table 1. Productivity of white clover in two-component stands with grasses (1991-1996, two field trials average, five years of utilization, three cuts), t ha^-1.

Fertilizer N promoted the development of grasses over white clover. Due to interspecific competition for light, white clover ratio was by 8.4 to 14.5 percent lower in all mixed swards which received fertilizer N compared to treatments without fertilizer N applications. Starting with the third year of sward utilization, creeping grasses showed a negative influence on the content of white clover on these soils. Stable white clover was in mixtures with smooth meadow grass, white hair-grass, perennial ryegrass, red fescue, meadow fescue and timothy. Tall and phytocenotically active grass species, such as meadow foxtail, cocksfoot, tall or false oat grass, upright brome and tall fescue, significantly reduced the content of white clover in a stand, particularly under three-cut treatments. It must be noted that perennial ryegrass under adequate moisture conditions in soil in the first two years of sward utilization, and red fescue with the second year of sward utilization, adversely effected white clover content in a binary clover-grass sward, particularly when receiving fertilizer N.

Table 2. Productivity of white clover in two-component stands with grasses (1991-1996, two field trials average, five years of utilization, five cuts), t ha^-1.

CONCLUSIONS

1. White clover in binary mixtures with grasses contribute to the production of high quality herbage swards with the average yields of dry matter 6.06 to 6.98 t ha-¹ and crude protein 1.14 to 1.75 t ha-¹ on brown-lessive and sod-podzolic gleysolic soils under conditions in Latvia.

2. Five-cut treatments of mixed white clover-grass swards have a beneficial effect on white clover content in a sward compared to three-cut harvest regimes but lead to a lower productivity of a sward.

3. White clover in binary clover-grass stands is most stable starting with the third year of sward utilization. Even with inadequate fertility, fertilizer applications are recommended only in the third year of sward utilization.

4. White clover survives best with companion bottom grasses and with meadow fescue and timothy in mixtures. The presence of early upper cauline-leaves grasses essentially reduces white clover content in mixed clover-grass stands.

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