White clover seed rate and ratio with grasses for pasture swards

Zydrè Kisonaitè and Leonas Kadziulis

Lithuanian Institute of Agriculture,
Dotnuva-Akademija, Kèdainiai 5051, Lithuania

Introduction
Materials and methods
Results and discussion
Conclusions
References

Introduction

White clover is the main legume for cultivated pastures in Lithuania comprising about 700,000 hectares (more than a fifth of fanning land). Pasture swards need renovation every few years. Therefore large amounts of perennial legume and grass seeds are used every year and white clover seed is mostly in limited supply.

The main role of white clover in pastures is N fixation. Due to this biological N, DM yields of grass/clover swards are: in Great Britain, 8-101 ha^-1 (Laidlaw, 1990; Frame, 1992), in the central region of Russia, 4-6 t ha^-1 (Novoselova and Frame, 1992), in Estonia, 4-6 t ha^-1 (Viiralt and Kabanen, 1985), and in Lithuania 5.5-7.0 t ha^-1 (Kadziulis and Tonkünas, 1970; Gutauskas and Bilevicius, 1989).

Although having good agronomic properties, white clover varieties bred in Lithuania have limited productivity due a weak competitive capacity when associated with grasses. However, the newer variety, Atoliai, is taller, has large leaves and is more competitive with grasses (Virbickienè et al., 1980). Seed productivity of white clovers, especially of this variety, is low, so it is important to use clover rationally in seed mixtures. Nevertheless, white clover seed rates in mixtures and ratio with grasses had not previously been investigated in Lithuania.

Materials and methods

In 1987 and 1988, two trials with a late sward, and in 1988 and 1989 trials with a medium early sward, were sown as re-established pastures. Each trial was continued for five years (sowing year and 4 use years).

There were two factorial trials: 'A' factor - seed rate of white clover and ratio with grasses in seed mixture (see Table 1); 'B' factor - N fertilization in sward use years. Treatments of 'A' factor: 1) 10% white clover + 90% grasses, 1 seed rate of mixture; 2) 20% white clover + 80% grasses, 1 seed rate; 3) 30% white clover + 70% grasses, 1 seed rate; 4) 40% white clover +60% grasses, 1 seed rate; 5) 30% white clover + 70% grasses, 1.33 seed rate; 6) 30% white clover + 70% grasses, 0.67 seed rate; 7) 30% white clover + 70% grasses, 0.33 seed rate. Treatments of 'B' factor: 1) P₆₀K₆₀, without N fertilizers; 2) P₆₀K₆₀N₆₀ for late (N₃₀ after II and III grazings) and P₆₀K₆₀N₉₀ for medium early sward (N₃₀ after I, II and III grazings). Pasture swards were grazed by dairy cows 4-5 times during the season and available DM yield, residues of DM yield after grazing and botanical and chemical composition were measured for every grazing.

The soil was a soddy gleyic loam. At the beginning of the trials the content of humus was 3.3-3.9%, pH_KCl -6.9, available P₂O₅ -222 to 282 and K₂O -97 to 179 mg kg^-1.

The seed mixtures were sown with an oat + vetch (100 + 50 kg ha^-1) cover crop utilized as green forage. The seed mixture of them late sward consisted of Trifolium repens L. cv. Atoliai, Phleum pratense L. cv. Vèlenis and Agrostis stolonifera L. cv. Guoda and in the medium early sward, Poa pratensis L. cv. Danga, Festuca pratensis Huds. cv. Dotnuva I and Trifolium repens L. cv. Atoliai.

Meteorological conditions over the experiment years were very diverse, ranging between normal (1987), wet (1989 and 1993) and droughty (1992).

Results and discussion

White clover seed rates and ratio with grasses and total seed rate of the mixture had some influence on sward establishment in the sowing year. The cover crop cut for green forage yielded 2.0-3.91 DM ha^-1 and did not adversely affect the underseeded clover.

The percentage of white clover emergence was similar in all the treatments but more plants were present, where the highest clover seed rate was sown. Ratio with grasses had little effect (Table 1). The number of white clover plants in the medium early sward was lower than that in late sward. This might have been influenced by the development of more competitive grass species. Differences in white clover plant number after germination were nearest to the differences in seed mixture, but by autumn these differences decreased and were very small in the next spring. White clover seed rate and ratio with grasses had an insignificant influence on establishment of both swards in the 1^st and 2^nd year of use and still less affected the sward composition in subsequent years.

Table 1. White clover growth in swards from sowing up to the first grazing in next (1^st use) year (2 trials, average data, 1987-1990)

Seed rate, kg ha-1		In mixture		Plants, No m-2			Tillers, No m-2		1st use
Total	White clover	%	No m-2	After germination	In autumn	In spring 1st usage year	In autumn	In spring 1st use year	year, 1st grazing, %
Late sward:
10.9	1.0	10	141	52	71	66	641	363	10.0
10.8	2.0	20	282	88	104	56	694	290	20.5
10.7	3.0	30	423	102	132	78	909	446	18.5
10.6	4.0	40	564	152	150	104	956	530	25.3
14.3	4.0	30	564	166	171	102	1124	519	20.5
7.1	2.0	30	282	80	115	91	828	473	20.5
3.6	1.0	30	141	40	67	64	644	428	15.3
LSD05				31.5	35.0	27.4	216.7	155.0
Medium early sward:
14.5	1.0	10	143	26	30	20	282	106	13.3
14.0	2.0	20	286	64	69	38	678	258	14.5
13.5	3.0	30	428	77	79	33	696	248	16.8
13.0	4.0	40	571	118	92	48	744	349	19.6
18.0	4.0	30	571	78	69	39	579	248	16.6
9.0	2.0	30	286	48	57	32	632	252	17.2
4.5	1.0	30	143	26	33	24	362	184	14.3
LSD05				28.5	29.9		226.6

White clover amounted more than 40% of DM yield in both swards in the 1^st and 2^nd years of use, when no N was used. It markedly decreased in the 3^rd and 4^th year, but it remained rather high (20.9-29.1% with the late, 31.7-37.1% with the medium early swards) in the 4^th year. Nitrogen application (N_60-90) produced a negative influence on the white clover growth only in the 2^nd and subsequent years of sward use, and clover content decreased on average by 8.3-11.5 percentage units.

No significant differences in average total DM yield data from the four years of sward use of both swards were obtained (Table 2). Even the highest total seed rates and of white clover did not markedly influence DM, total metabolizable energy (ME) or crude protein (CP) yields. There were significant differences in white clover DM yield. It increased with increasing seed rate from 1 to 4 kg ha^-1 and at the same time improved the amount of clover in mixture. Seed ratio was more important for clover than its seed rate.

Table 2. The influence of white clover seed rate and ratio and nitrogen fertilization on late and medium early pastures (4 trials, average data, 1988-1993)

Seed rate, kg ha-1		N kg ha-1	Botanical composition,							DM utilized, %
			%			Yields
Total	White clover		White clover	Grasses	Forbs	DM, t ha-1		CP, kg ha-1	ME, GJ ha-1
						Sward	White clover
Late sward (I-IV use years):
Factor A - seed rate and ratio
10.9	1.0	0-60	30.1	50.9	19.0	6.95	2.08	1347	76.18	81.9
10.8	2.0	0-60	33.4	50.1	16.5	7.31	2.44	1451	80.95	82.5
10.7	3.0	0-60	36.8	47.2	16.0	7.30	2.68	1466	80.88	83.7
10.6	4.0	0-60	37.0	48.9	14.1	7.19	2.67	1440	79.33	83.0
14.3	4.0	0-60	32.0	48.8	19.2	7.06	2.37	1397	77.39	83.1
7.1	2.0	0-60	35.0	48.2	16.8	7.29	2.54	1454	80.74	82.3
3.6	1.0	0-60	34.2	47.5	18.2	7.08	2.42	1428	77.80	82.1
LSD05			2.94	3.45	1.36	0.455	0.085	91.2	5.02	-
Factor B - nitrogen fertilization in sward use years
		0	38.4	45.1	16.5	6.95	1.20	1395	76.86	83.2
		60	30.1	52.3	17.6	7.37	0.88	1457	81.20	82.0
LSD05			2.94	1.75	0.84	0.128	0.036	26.1	1.44	-
Medium early sward (I-IV use years):
Factor A - seed rate and ratio
14.5	1.0	0-90	28.9	59.0	12.1	7.46	2.17	1473	79.99	79.9
14.0	2.0	0-90	30.7	57.7	11.6	7.48	2.29	1514	81.00	81.3
13.5	3.0	0-90	30.6	55.7	13.7	7.62.	2.33	1527	81.97	81.4
13.0	4.0	0-90	31.6	57.1	11.6	7.43	2.32	1496	80.22	81.8
18.0	4.0	0-90	31.6	56.6	11.8	7.74	2.45	1563	83.76	81.4
9.0	2.0	0-90	31.0	55.0	14.0	7.41	2.30	1460	79.41	82.9
4.5	1.0	0-90	31.2	52.5	16.3	7.58	2.36	1531	81.73	83.9
LSD05			2.41	2.63	1.00	0.342	0.105	72.7	3.740	-
Factor B - nitrogen fertilization in sward use years
		0	36.8	50.7	12.5	7.15	2.62	1454	77.57	82.1
		90	25.3	61.2	13.5	7.87	1.98	1563	84.72	81.3
LSD05			1.40	1.61	0.78	0.083	0.025	17.6	0.900	-

Improving clover:grass ratio up to 30:70, but retaining clover seed at 1 kg ha^-1, resulted in white clover DM yield being lower only in comparison with more favourable ratios (40:60) and at a higher (4kg ha^-1) clover seed rate. Yields of both swards, when sowing small rates and at a favourable (30:70) ratio for clover, differed little from the yield when in higher total rates and other ratios were sown.

Application of N increased DM and CP yields significantly, but DM response to N was low, 7-8 kg of DM per kg N applied. White clover seed rate and ratio did not influence the percentage utilization significantly but botanical and chemical composition of the residual DM was poorer than that of the total herbage DM. Application of N increased the total amount of residues, but the percentage utilization was not affected.

Conclusions

White clover seed rates and ratio with grasses had some influence on pasture sward establishment in the sowing year, but it was not very important factor in subsequent four years of use by dairy cows.

Botanical composition and DM yield in late and medium early swards varied a little depending on the white clover and total mixture seed rates, but varied slightly more according to the clover:grass seed ratio.

Application of N_60-90 slightly, but significantly, increased DM yield, but decreased clover content by about 10%.

The most important result obtained in these investigations is the possibility of reseeding pasture by sowing low seed rates of total mixture (3.6-4.5 kg ha^-1) when white clover:grass ratio is favourable and a good variety of white clover is used.

References

FRAME, J. (1992) Improved Grassland Management. Farming Press, Ipswich, p.351.

GUTAUSKAS, J. and BILEVICIUS, V. (1989) Ankstyvuju ir vèlyvuju ankstiniu-varpiniu ganykliniu zolynu naudojimo daznumas. Zolininkvstè. No. 64, pp. 68-76.

KADZIULIS, L. and TONKUNAS, J. (1970) Nitrogen responses of legume-grass pastures in Lithuania. Proceedings XI International Grassland Congress. Surfers Paradise, Australia, pp. 397-400.

LAIDLAW, A.S. (1990) The effect of method and time of sowing on white clover production in mixed swards. Proceedings of the 13th General Meeting of the European Grassland Federation. Banska Bystrica, Czechoslovakia, Vol. I, pp. 272-275.

NOVOSELOVA, A. and FRAME, J. (1992) The role of legumes in European grassland production. Proceedings of the 14th General Meeting of the European Grassland Federation. Lahti, Finland, pp. 87-96.

VIIRALT, R. and KABANEN, N. (1985) Effektivnost i vzaimodeistvija azotnogo udobrenija na dolgoletnih zlakovom i polzuchekleverno-zlakovom travostojah. Rol i perspektivy biologicheskogo i mineralnogo azota b intensivnom lugovodstve. Tartu. Estonia, pp. 50-53.

VIRBICKIENE, S. et al. (1980). Baltuju dobilu veislè 'Atoliai'. Zoliu ukis: Moksl. str. rink. No. 40, pp. 58-64.