Mechanisation to achieve rapid wilt
Work at the ARINI, Hillsborough has examined techniques and systems that aid rapid wilting of perennial ryegrass to a target dry matter of 25 percent. The conclusions from this work are that dry weather, sunshine and spreading of the grass are the most important factors.
Spreading and Conditioning
Table 4 indicates that grass cut on any dry day during the silage season can reaspma; 25 percent dry matter within 32 hours. From the data in Table 4 it is apparent that, on average:
- wilting rate in average sunshine (hazy summer day) is 2.4 times that in dull sunshine (overcast summer day);
- a double row wilts at less than half the rate of a single row;
- a spread crop wilts at more than twice the rate of a single row;
- mower conditioned grass wilts 20 percent faster than unconditioned grass.
Table 4. Effect of row type and sunshine on grass dry matter percent after 8 and 32 hours of dry weather in the field (initial dry matter 13 percent; fresh yield 30 t/ha)
| Dull sunshine | Average sunshine | |||||||
|---|---|---|---|---|---|---|---|---|
| Unconditioned | Conditioned | Unconditioned | Unconditioned | |||||
8 hrs |
32 hrs |
8 hrs |
32 hrs |
8 hrs |
32 hrs | 8 hrs |
32 hrs | |
| Double Row | 14.4 |
15.5 |
14.6 |
16.0 |
15.6 |
18.2 |
16.1 |
19.3 |
| Single Row | 15.5 |
18.0 |
16.0 |
19.0 |
18.3 |
24.6 |
19.4 |
27.3 |
| Completely Spread | 17.6 |
22.9 |
18.6 |
25.3 |
23.5 |
38.0 |
26.1 |
44.7 |
Tedding
The tedding of grass after cutting improved the rate of wilting (Table 5), however the benefit was small compared to the benefits from sunshine and spreading.
Table 5. Effect of tedding and sunshine on grass dry matter concentration after eight hours of dry weather in the field (initial dry matter 13 percent; fresh yield 30 t/ha)
Dull sunshine |
Average sunshine |
|||
|---|---|---|---|---|
| Without tedding | With tedding | Without tedding | With tedding | |
| Spread swath | 17.6 |
18.3 |
23.5 |
25.3 |
Mowing and Spreading
There are machines on the market now that mow, condition and spread grass in one pass. This type of machine has proved to be very effective (see Table 5). It should be noted from the data presented that completely spreading an unconditioned crop gave a faster wilting rate than leaving a conditioned crop in a row. The fastest wilting rate was obtained by spreading a conditioned crop.
Table 6. Dry matter of grass after nine hours dry weather in the field (mean of eight experiments over 1997 and 1998; initial dry matter 16 percent)
| Unconditioned single row | Unconditioned and completely spread | Conditioned single row | Conditioned and completeley spread | |
|---|---|---|---|---|
| Final dry matter(%) | 22 |
28 |
26 |
31 |
| Relative drying rate | 100 |
160 |
140 |
180 |
Field Losses
In the work at Hillsborough field losses from mowing and picking up were in the order of 3 percent of the grass dry matter. An additional 1-3% dry matter loss resulted from spreading and rowing-up. Within these values the dry matter losses that followed conditioning were slightly greater than those from the unconditioned grass. Rainfall on conditioned grass gave up to four times more dry matter loss than from unconditioned grass (up to 8 percent depending upon degree of conditioning).
Summary
Where rapid wilting is required, the recommendations are, in order of importance:
- Cut in dry weather.
- Spread the grass at cutting if possible.
- Cut when bright sunshine is forecast.
- Condition the grass at cutting.
Note: The wilting of grass may increase silage harvesting costs by up to 10 percent. This is due to the need to row up a spread crop prior to lifting.