Catch Crops for Feed Production in Drought Conditions

Frick R., Dereuder E., Coudry C., Raymond B., Dubois S., Mariotte P., Probo M., Wyss U.

Original article appeared in Swiss Agricultural Research

04.07.24

Photo: Rainer Frick,
Agroscope

Are drought-tolerant catch crops a good source of feed? A trial conducted by Agroscope shows that their potential is limited. Combining certain of these catch crops with legumes can improve feed quality, including in the form of silage.

In regions where summer droughts are common there is a growing interest in drought-tolerant catch crops for feed production. In 2021, Agroscope conducted trials on three farms in the Canton of Jura with five alternative catch crops: pure stands of multi-cut forage sorghum; multi-cut forage sorghum with clover; and bristle oat with pure stands of crimson clover, moha and pearl millet, respectively. A mix consisting of oats, peas and common vetch, equivalent to Standard Mix (SM) 101, served as a reference crop. The aim of the study was to investigate the suitability of these alternative crops as catch crops as well as their yield potential and feed quality. On one of the three trial sites the forage of the six variants was ensiled in round bales to analyse the quality of the conserved silage (forage composition values, nutritional values, fermentation quality).

Low yields and forage composition values improved by clover

Due to the very wet conditions in July 2021 and the resulting difficulties with sowing, yields were generally low, averaging 24dt DM per ha. In favourable growth conditions, 30 to 40dt DM/ha can normally be obtained with catch crops sown in summer.

The lowest DM yields were obtained with pearl millet (17dt DM/ha) and pure sorghum (21 dt DM/ha). Bristle oat with crimson clover performed slightly better, with 24dt DM/ha. At 29dt DM/ha yields of sorghum with berseem clover and Persian clover were better, thanks to the high proportion of legumes in the mixture (50%). The highest yields – nearly 31dt DM/ha – were obtained with moha, which appears to better withstand wet conditions (fig. 1). SM 101 produced yields of 25dt DM/ha.

Fig. 1: Moha, a plant originating in Africa, produced yields of satisfactory quantity but of mediocre forage quality (Rainer Frick, Agroscope).

Crude protein yields were also modest. Only sorghum in combination with the annual clovers (fig. 2) produced a protein yield of 500kg/ha thanks to the high proportion of clovers in the mixture. The silages produced from moha, pearl millet and sorghum in pure stands yielded fairly unsatisfactory results in terms of forage composition and nutritional value, with 4.6 to 5.3MJ NEL (net energy of lactation) and 63 to 74g API (absorbable proteins in the intestine) per kg DM. For bristle oat with crimson clover as well as for the sorghum-clover mixtures, forage composition and nutritional values were better thanks to the legumes in the forage.

Fig. 2: Multi-cut forage sorghum is a fast-growing crop. It can only be recommended if grown in combination with annual clovers (Rainer Frick, Agroscope).

Thorough wilting for good silage

At harvest, DM content of the green forage of the six variants was very low (15 to 19%). By contrast, the fermentation quality of the ensiled forage was good, thanks to an adequate degree of wilting yielding 30% DM and a low degree of contamination of the feed with earth. Despite the fairly high pH values, acetic and lactic acid content were within the normal range. Butyric acid was only present in the SM 101 and bristle oat silages.

Conclusions

Sorghum, moha and pearl millet, all of which are drought-adapted plants, do not crop reliably in our latitudes, where the climate is characterised by significant fluctuations (dry but also wet years).
The quality of the feed yielded by these crops is mediocre, comparable to the first cut of extensive-meadow hay. It can only be recommended to alleviate feed shortages and for rearing heifers or small ruminants.
The protein and energy content of these crops can be improved by combining them in mixtures with over 30% annual legumes (Persian or berseem clover).
Despite the mediocre forage composition values of the basic ration, it is possible to produce a silage of satisfactory quality provided that the forage is adequately wilted beforehand (i.e. contains over 30% DM). The use of an ensiling agent is, however, recommended.