Ton Baars, Marian van Dongen and Liesbeth Brands
Louis Bolk Instituut, Department of Organic agricultural science,
Hoofdstraat 24, 3972 LA Driebergen, The Netherlands
Introduction
Materials and methods
Results
Discussion and conclusions
Acknowledgements
References
In the experience of organic farmers the start of the grazing season and the time of the first cut is delayed by about 10-14 days in comparison with conventional farmers using fertilizers. In organic agriculture the total amount of home-grown fodder as well as early spring growth are important factors for the economic results of the farm.
For improving early season growth two possibilities were investigated:
- the use of a new clover variety (AberHerald) as a more cold tolerant, winter hardy line (Rhodes and Fothergill, 1993);- the use of organic manure before the first cut to improve the mineral N status of the soil. This report gives the first two years' results.
The experiments were sown on 2 September 1992 on a moist, sandy soil. A pasture was ploughed in the last week of August and sown with perennial ryegrass cv, Magella (30 kg ha-1). Three white clover varieties were sown by hand, cvs AberHerald, Alice and Retor (3 kg ha-1). Three manuring treatments were investigated: shallow injection of cattle slurry (4-5 cm depth), composted farmyard manure (from a deep litter shed) and only P and K. In 1993 manure was given directly after the first cut, in 1994 before the first cut (20 april). Amounts of manure were used to supply 100 kg N ha-1 (circa 22 m3 slurry or 20 t FYM), being a normal level of manuring on organic farms. The influence of clover on the yield was measured by comparison with the yield of grass without clover. There were two trials each with five defoliations, namely a wholly cutting trial within which grazing was simulated by cutting at a DM yield of 1.7 to 2.0 t ha-1 for the 1st, 3rd and 5th defoliation while conservation cuts at yields of 2.5 to 3.0 t ha-1 were made at the 2nd and 4th defoliations. In the second trial the same management regime was implemented but the grazing defoliations were carried out by dairy cows. Each trail had a 4-replicated randomized-block design but because of the machinary involved, the manuring treatments were not fully randomized. Plot size was 10 × 3 m (simulated grazing trial) and 10x6 m (real grazing trial). All grazing plots within a trial were grazed at the same time. Yields were measured the day before each cut or grazing period, harvested with a Haldrup leaving 5 cm stubble height. Aftermath was measured directly after a two days grazing period. Clover content was measured by hand separation of herbage samples. Clover stolon length and weights were measured from samples (6 cores per plot) taken 6 weeks after spring manuring and again in November. In 1994 clover samples were taken to examine leaf damage caused by molluscs (method, after Clements et al. 1992).
Weather
In November 1993 minimum temperatures were -9.7 °C, in February 1994 -11.9 °C. April and May 1994 were very rainy and cold.
Herbage yield and clover development (cutting trial)
In the first year growth of annual weeds was important (mainly Capsella bursa-pastoris). especially in the first and second cuts (44% and 5% in DM respectively). The effect on total herbage DM yield of clover in the mixture in relation to the grass-only sward was about 3,8 t ha' in both years; there was no effect from manure and variety on total herbage yield. In spring 1994 there was no effect from variety and manure on total herbage DM yield at the first cut.
Table 1. Total and clover yield in cutting trial, 1993 and 1994; also yield and clovercontent at first cut, 1994; varieties (mean of three manuring treatments) and manures (means of three clover varieties).
|
|
total DM (t ha-1) |
Clover DM (t ha-1) |
1st cut in 1994 |
||||
|
1993 |
1994 |
1993 |
1994 |
t DM ha-1 |
clover (% in DM) |
||
|
Grass only |
7.93 |
6.58 |
0.12 |
0.00 |
2.32 |
0.0 |
|
|
Grass plus: |
|||||||
|
|
Alice |
11.77 |
10.60 |
4.77 |
5.01 |
2.52 |
35.1 |
|
|
Retor |
11.66 |
10.21 |
5.01 |
3.28 |
2.46 |
31.9 |
|
|
AberHerald |
11.75 |
10.56 |
5.15 |
5.20 |
2.38 |
41.5 |
|
Significance |
NS |
NS |
NS |
*** |
NS |
* |
|
|
Manures: |
|||||||
|
|
P + K |
11.29 |
9.95 |
5.51 |
4.17 |
2.32 |
43.7 |
|
|
Slurry |
12.06 |
10.62 |
4.07 |
4.26 |
2.48 |
27.3 |
|
|
FYM |
11.85 |
10.81 |
5.35 |
5,06 |
2.56 |
37.8 |
|
Significance |
NS |
NS |
** |
** |
NS |
*** |
|
There was no difference in development between Alice and AberHerald. From the 5th cut in 1993 cv. Retor declined. In the 3rd and 4th cut of 1994 damage by slugs was measured (Table 2). In both cuts leaf damage in Retor was about twice as much as in the other varieties.
Table 2. Damage by molluscs in white clover in 1994 (% of total clover leaf eaten).
|
|
3rd cut |
4th cut | |
|
Grass plus: | |||
|
|
Alice |
11.5 |
7.1 |
|
|
Retor |
25.4 |
13.0 |
|
|
AberHerald |
14.0 |
8.8 |
|
Significance |
*** |
* | |
Herbage yield and clover content (grazed trial)
There were no differences between the three clover varieties. The effect of manuring treatment on total and clover DM yields were about the same as under cutting (Table 3).
Table 3, Total and clover DM yield in grazing trial, 1993 and 1994; varieties (mean of three varieties) and manures (means of three clover varieties).
|
|
Total DM (t ha-1) |
Clover DM (t ha-1) |
|||
|
1993 |
1994 |
1993 |
1994 |
||
|
mean of 3 clovers |
10.17 |
9.84 |
3.74 |
3.85 |
|
|
Manures: |
|||||
|
|
P + K |
9.79 |
9.40 |
3.85 |
3.27 |
|
|
Slurry |
10.38 |
10.06 |
3.06 |
3.75 |
|
|
Compost |
10.35 |
10.06 |
4.20 |
4.54 |
|
Significance manures |
* |
NS |
*** |
*** |
|
There was no effect of clover variety on early crop yield, a result in agreement with Sheldrick et al. (1993). There was no difference between slurry injection or composted FYM on the total herbage yield or on the first growth in spring. Because of the late manuring in 1994, being too wet, the time between manuring and first cut was too short and N from the manure had little effect.
The development of white clover was the best when FYM was used. Especially in the first year there was a negative effect on clover development from slurry injection. In the first year slurry was given directly after the first cut. From the 4th cut in the second year the clover amount was the same under slurry and FYM. The negative effect of slurry on clover might be related to the stage of development of clover. During the first 18 months the tap root of clover was still there. Schils et al. (1992) found no negative effect of slurry injection on the development of full-grown white clover on a young clay soil.
Differences between varieties were small under rotational grazing in relation to the cutting regime. The decline of cv. Retor in the second year was significant under cutting, but not under rotational grazing management. To be more relevant to farming practice variety testing should be done more under grazing as well as under cutting.
The clover variety Retor is eaten more by slugs than the other two varieties. There is a direct relationship between slug damage and cyanide concentration (HCN) in the plant. In the Swiss National List varieties with a cyanide concentration above 450-500 mg kg-1 are not listed. For example, the variety Alice has a concentration of 1350 mg kg-1 (Lehman, FAP Zürich Reckenholz, pers. comm.). From a breeding point of view more cyanide is interesting in relation to resistance to slugs. On the other hand clover plants have to be eaten by ruminant animals. So more information about the negative effects of HCN on animal health is needed.
This project is financed by the European Union (AIR-program). Project title: Organic farming: nutritional, environmental and economic implications of conversion.
CLEMENTS, R.O. and MURRAY, P.J. (1992). Second report of an ecological study of pest and disease damage to white clover in England and Wales. AFRC Institute of Grassland and Environmental Research. Hurley, Berkshire.
RHODES, I. and FOTHERGILL, M. (1993). White clover breeding. AFRC Institute of Grassland and Environmental Research. 1992 Report, pp. 33-34.
SCHILS, R.L.M. and SIKKEMA, K. (1992). Zodebemesting op gras-klavermengsels; het 'snij-effect' In: Praktijkonderzoek 5e jaargang nr. 1, februari 1992, pp. 1-3
SHELDRICK, R.D., LAVENDER R.H. and MARTYN T.M. (1993). A field evaluation of two white clover cultivars selected for winter hardiness. FAO REUR Technical Series. 29, 91-93
