Silage Insights - Research
A comparative study on pre-wilting techniques: wide-spreading and swathing

By Per Lingvall, Martin Knický, Thomas Pauly, Rainer Nylund, Johan Andersso, Rolf Spörndly, Stephan Ackermann and Lucas Winkelmeier

The results of this study by the Swedish University of Agricultural Sciences show that it is easier to achieve dry matter content levels for good silage quality with the wide-spread crop technique.

Materials and Methodology

During the first cut of silage, 20 ha of clover/grass ley have been divided into two equal parts. One part of the crop was left wide-spread while the second part was made into swaths. See picture 1.		The wide-spreading was performed by a front mounted Pöttinger Novacat 306 FED and a side mounted Pöttinger Novacat 305 HED on the same tractor. The swathing was performed with a front mounted Pöttinger Novacat 306 FED and a towed Pöttinger CatNova 3200T with side elevator creating one “double” swath. See pictures 2 and 3.
Picture 1. 20 hectares split into one part wide-spreading and one part for swathing. Photo: Swedish University of Agricultural Sciences		Pictures 2 and 3. To the left a front and side mounted mower producing a wide-spread material and to the right a front mounted and towed mower producing a swath. Photo: Swedish University of Agricultural Sciences
The objective was to register the effectiveness of the two methods in the wilting process. When one of the two methods reached a 40% dry matter (DM) level, the pressing of round bales began. The wide-spread crop was put into swaths prior to the round baler pressing with a Pöttinger Eurotop 771 A. See picture 4.
Picture 4. Swathing of the wide-spread crop just before pressing to round bales Photo: Swedish University of Agricultural Sciences

The crop, consisting of meadow fescue, timothy, red clover and dandelion (50/40/5/5) was cut at 3:00pm on June 7^th, 2007. Some rain, approximately 2-4 mm, was experienced soon after, which resulted in DM content to drop slightly - more in the wide-spread crop and less so in the swathed crop, as the latter had not been exposed to the rain in the same way. The following day, weather was sunny, partly cloudy, no rain. Both crops remained untouched on the field until a 40% DM level was reached.

Results

The wide-spread crop reached 40% DM at about 4:00pm on the June 8^th. At that point the crop that was in swath only had a DM content of about 30 %. At this time the ensiling in round bales began. The wide-spread crop was put into swaths just before the baler and the DM measurements continued during the evening until the harvest was finished at 10:00pm. The drying process is illustrated in figure 4.

Figure 4. Drying up during the wilting process from mowing between 3:00pm and 10:00pm the following day. The pressing of round bales started at 4:00pm on the second day. Source: Swedish University of Agricultural Sciences

The wide-spread treatment not only reached 40 % DM faster, but the variation in DM in the crop was significantly lower. Figure 5 illustrates how the thinner layer of the wide-spread crop varies very little in DM content between the lower and upper layer.

Figure 5. DM content in the upper layer (Top) and the under layer (Bottom) in wide-spread and the swathe crop during the wilting process Source: Swedish University of Agricultural Sciences

When the crop in the swath had a mean DM content of 30 % at 24 hours after mowing, the top layer was about 40 % DM while the bottom layer still was approximately 20 % DM.

What about the silage quality?

Ensiling in round bales started when the wide-spread treatment reached 40% DM. The DM in the swathed treatment was at that point only 30%. The resulting silage quality differed significantly in the way that is to be expected with different DM contents. The wide-spread treatment gave a good quality of silage while the swathing produced silage with twice the amount of ammonia and a high concentration of butyric acid. DM loss was twice as high in the swathed silage, and bale density was 30% higher in the widespread. Silage quality parameters are presented in Table 1.

Table 1. Silage quality, density and DM losses in round bales produced from green crop wilted wide-spread or in swaths after 24 hours.
	Wide spread		Swathed
	Mean	Sd	Mean	Sd	Sign.
DM, g/kg	416	24.2	285	17.2	***
pH	5.2	0.09	4.8	0.13	***
NH3-N (g/kg TN)	65.1	11.38	109.6	14.87	***
WSC, g/kg ts	86.0	11.92	43.2	15.33	***
Lactid acid, g/kg ts	15.4	4.69	39.6	10.74	***
Acetic acid, g/kg ts	3.6	0.90	8.8	2.89	***
Butyric acid, g/kg ts	0.4	0.08	7.3	4.35	***
Ethanol, g/kg ts	12.2	3.35	14.7	2.54	***
2.3-butanediol, g/kg ts	3.1	0.56	13.9	3.21	***
Density, kg ts/m3	181	12.8	137	9.7
DM loss, % of DM	1.9	0.61	4.5	12.8
Sign *** = probability that the means are equal is less than 0,01 % sd= standard deviation
Source: Swedish University of Agricultural Sciences

Cost considerations

By using the wide-spread technique instead of swathing it was possible to make high quality silage within 24 hours even though there had been some rainfall. However, the wide-spread method required more work since one has to drive across the field once more to swath the wide-spread crop immediately before pressing the round bales. Table 2 shows the costs involved in the two treatments.

It can be seen from Table 2 that almost twice as much work is performed in the wide-spread crop compared to the swathed crop, and that in pressing a drier crop one can gain time since bales with higher DM are produced faster and more efficiently.

Table 2. Some measures of effectiveness at round baling from wide-spread and swathed crop respectively
	Wide-spread	Swathed
Mowing
Tractor	Massey Ferguson 6840	Massey Ferguson 6290
Acerage	11 ha	9 ha
Labour	147 minutes	161 minutes
Mowing capacity	4.49 ha/h	3.35 ha/h
Diesel consumption	5.3 litre/ha	6.2 litre/ha
Swathing
Tractor	Massey Ferguson 390T	-
Acerage	11 ha	-
Labour	141 minutes	-
Swathing capacity	4.68 ha/h	-
Diesel consumption	1.2 litre/ha	-
Manpower need for:
Mowing	1 person	1 person
Swathing	1 person	-
Pressing
Weight of bales	341 kg ts/bale	269 kg ts/bal
Capacity	170 kg ts/minutes	117 kg ts/minutes
Diesel consumption	1,4 l/ton DM	1,9 l/ton DM
Source: Swedish University of Agricultural Sciences

Conclusions and Discussion

By spreading the crop in a thinner layer the wilting process runs faster. This trial has also shown that the timing of the silage production on the same day or a day later can have a great significance. To postpone the ensilage an extra day can be detrimental if rain continues. This explains what happens when silage is often produced with a low level of dry matter contents, you get a low level of silage quality as the consequence.

The use of wide-spreading technique is often criticized as it requires more labour including one extra drive across the field for swathing the crop prior to the silage making. This extra work needed in the wide-spread system takes about the same time as the mowing for the wide-spread method, however the machine is cheaper and the diesel consumption lower.

Calculating with a contractor rate of 800 Swedish Krona (SEK¹) or 86.13 EUR/h for mowing and 700 SEK or 75.37 EUR/h for swathing and a yield of 4 500 kg DM per ha the system of wide-spreading has a cost of 7,30 SEK or 0.79 EUR per 100 kg DM (4,0 + 3,3 SEK) or (0.43 +0.36 EUR), to be compared with 5,3 SEK or 0.57 EUR per 100 kg DM (5,3 + 0 SEK) or (0.57 + 0 EUR) for the swathing system using the capacities measured in this trial.

If the result of the systems is that round bales of 40 % are produced from the wide-spread system and 30% from the swathed system the cost of producing the round bales will be lower in the wide-spread system. With a contractor rate of 1 200 SEK/h or 129.19 EUR/h it will be 12 SEK or 1.29 EUR/100 kg DM for the wide-spread bales and 17 SEK or 1.83 EUR/100 kg DM for the swathed bales. The total cost of harvesting and storing the silage in this trial would therefore be 19 SEK or 2.04 EUR/100 kg DM for the wide-spread and 22 SEK or 2.37 EUR/100 kg DM for the swathed technique.

A general conclusion is that it is easier to achieve DM content high enough for good silage quality with the wide-spread technique. Also the cost for the extra labour involved is lower in comparison to the potential gains.

¹ SEK= about 0.11 EUR (http://www.xe.com/ucc/)

A trial at the department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden
By Per Lingvall, Martin Knický, Thomas Pauly, Rainer Nylund, Johan Andersson and Rolf Spörndly at the University of Agricultural Sciences and Stephan Ackermann, Lucas Winkelmeier at Pöttinger AG, Austria.

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