Intercropping is a promising approach for low input agricultural systems such as organic farming. In central Italy, the use of intercropping is well known amongst organic farms combining crop and animal production. As part of DIVERSify, we worked with two organic farms as well as conducting our own plot and field scale trials at the University of Ancona (Università Politecnica delle Marche).
The link between crops and livestock farming, and the growing of forage crops, is very important because it offers a wider range of grain crops that the farmer can include in their crop rotations. Intercropping can also effectively deliver feed needs. For example, barley is a very important cereal that is used as an energy concentrate, whereas grain legumes such as faba bean and pea are important protein sources. On organic farms in the Marche Region, a good level of self-sufficiency for both grains and forages provides economic sustainability, allowing farmers to manage their feed costs and also avoid the risk of GM contamination in feed.
Fattoria San Martino, located at Monte San Martino (Province of Macerata) and managed by Bordò Flaviano, is an organic farm rearing beef cattle of the Marchigiana breed. It produces most of its own forage and feed grains (cereals and legumes), and buys the remaining part from local organic farmers. This farm, as with many other farms in the Marche Region, is familiar with the usefulness of barley-faba bean mixed cropping. Faba bean is a traditional grain legume that has been grown for a long time by the farmers to feed the Marchigiana cattle. However, less information is available to the farmers about the use of pea as an alternative to faba bean. The farmers were interested in trying peas instead of faba bean as it is higher yielding on average but little is known about this crop combination in this region. Therefore, the farm applied to be included in the DIVERSify project as Participatory Farmer for the 2018 growing season and carried out a field trial including the barley variety Tea and the pea variety Hardy. They also wanted to try different seed densities.
The field trial was set up as a Completely Randomised Block with 4 replicates, with plots of a large size (50 m length x 4,5 m width). The aim was to compare the two mono crops (Tea barley and Hardy peas) with 2 different mix combinations: MIX-A (barley 33% - pea 67%) and MIX-B (barley 25% - pea 75%). The percentages shown for each mix refers to the amount of seed of barley and pea included in the mix as a percentage of the seed used for the mono crops, respectively. At sowing time, barley and pea were totally mixed manually before drilling. The effectiveness of mixed cropping compared to mono crops was evaluated by the Land Equivalent Ratio (LER) index. This tells you whether a lesser or greater land area would be required to give the same yield of the crop in mono versus intercropping. A value greater than one indicates that a reduced area is required to give the same yield in the intercrop versus the monocrop (a yield advantage).
The field trial was sown on January 26, 2018 and harvested on June 29, 2018. The 2018 season was unfavourable to barley across all Italy and this trend was reflected in our field trial. However, interesting results supporting the validity of intercropping as a strategy for organic farmers were obtained. In particular, the LER was always higher than 1, with values around 1.3 for both 'MIX' combinations used. It was interesting to notice that the LER of barley was always higher than expected, whereas the LER of pea was always lower than expected. This suggested that barley's competitive ability against pea is quite strong. Even at a low sowing density, such as in the two 'MIX' combinations, barley showed a grain yield that is about 70% of that of barley as a sole crop.
Despite the importance of grain/seed yield, another very interesting aspect of this field trial needs to be mentioned, that is the ability of barley to counteract the presence of weeds such as wild mustard. As can be seen above, the field was characterised by the presence of 4 yellow stripes, that is the 4 plots hosting pea as a monocrop. All other plots, including barley as a monocrop and the two intercrop combinations, did not show, or showed at a much lower level, the presence of wild mustard. This effect of barley is described in the scientific literature and in this field trial it showed up very brightly. Subplot cuts were collected and data concerning single plants and the overall subplot were obtained to explore differences in more detail.
One of the main challenges of growing peas in the region is now the presence of wild boars (see picture below), they cause very bad damage to the crops and have a taste for peas over faba bean. It was interesting to see that paths caused by wild boar walking across the plots were most present in the monocrop pea plots. The very rainy season characterising 2018 spring and first part of summer led to very strong damages due to wild boars across all our region but growing the peas with barley seemed to reduce their ability to forage in this crop.
This trial has been conducted in 2018 as part of a larger programme of field trials carried out by the Università Politecnica delle Marche. In fact, the barley-pea intercropping approach was tested in another on-farm trial, carried out involving another organic farm located at Sterpeti (PU), and in one large-scale and one plot trial both realised at the University's experimental station. Subsequently, an overall analysis will gather the results of the whole set of trials. Stay tuned to hear more about these trials and see whether statistical analysis confirms the competitive effect of barley against weeds and the real danger to yield from wild boar damage. Overall, despite the challenges of weeds and pest damage, barley-pea intercropping seems like a good crop for organic farmers in order to diversify their crop rotation and to harvest grain in a mixture that can be directly used as animal feed.