Po Valley Rice Production

Rice growing in flooded field, Piemonte

This is a piece I wrote as a university report about rice production after our field trip on rice in May 2007 when we visited two producers in the province of Vercelli, Piemonte, Italy…

There are 25 species of rice of which only two have been domesticated. Of these, the Asian species Oryza sativa has been the most adopted and has been one of the most important staple foods in the human diet since the introduction of agriculture. Rice is thought to have been cultivated as early as 10,000 years ago in South-East Asia. Two main variants of O. sativa appeared, Indica from the Indian side of the Himalayas and Japonica from the Chinese side. The main characteristics being that Indica has longer, thinner grains and Japonica shorter, fatter grains.Rice was known in Europe in Greek and Roman times but, as with many new and exotic plant introductions, it was used more for medicinal purposes than a staple part of the diet. In the 15th century rice growing took off in Italy, the first records of growing in the Po valley are from 1427. In fact, the Po valley is one of the only places in Europe suitable for substantial growing of rice due to the need for reasonably warm temperatures and plenty of water. One of the attractions rice offered as a crop was its prodigious yield in comparison to other grains. Around 30 grains can be obtained for each grain sown. In the middle ages, wheat yields could regularly be as low as 3 grains for each sown. Before maize and potatoes were introduced from America, rice was one of the most productive food crops known.

For our thematic stage on rice we visited two producers near Vercelli in Piemonte. Cascina Veneria is a conventionally farmed estate and part of the Saiagricola company. While at Cascina Veneria we were very fortunate to have the services of Antonio Tinarello, author of books about rice and one of the most knowledgeable rice experts in Italy. Tenuta Colombara is the home of Acquerello rice, they only grow the Carnaroli variety with an organic farming system. We finished with a brief visit to the National Rice Research Centre at Castel d’Agogna near Mortara.

Italian quality rice production is dominated by Japonica varieties such as Carnaroli, Arborio and Vialone Nano which are especially suited for the cooking of risotto. Carnaroli is the “king” of these varieties and can command up to 5 times the price of other varieties. In terms of starch composition, Carnaroli also has the highest ratio of amylopectin to amylose of the common Italian varieties. Amylopectin is much more readily dissolved than amylose, making the rice stickier in cooking. Also it is more easily digestible, increasing the glycaemic index of the food.

At Cascina Veneria they produce a number of Italian varieties including Carnaroli, Baldo, Ballila, Vialone Nano, and some Indica varieties as well. Tenuta Colombara grows only Carnaroli, which simplifies production, packaging and removes the possibility of varietal mixing.

Until the advent of sophisticated agricultural machinery in the 1960s, rice growing in Italy was a highly labour-intensive endeavour. At Cascina Veneria
where they have 500 Hectares of land, they used to have 250 full-time workers with another 800 being employed in the busy summer months dealing with transplanting, weeding and harvesting. This period of life at Cascina Veneria is very nicely captured in the film Riso Amaro (Bitter Rice) a fiction film made in 1948 by Dino de Laurentis featuring the armies of women who used to travel to work in the rice fields.

Most rice is grown using wet paddy field systems. It is, however, possible to grow rice in dry fields but there are a number of benefits from using water. Firstly, the water prevents many types of weeds from over-whelming the rice. With water there are problems with aquatic weeds but these can be minimised by rotation of fields between wet and dry agriculture – Rice is grown in wet fields for 2 years in which time any non-aquatic weeds will be substantially diminished, then the field is used for dry farming for a year or two growing soya or barley etc during which time any aquatic weeds should die out ready for the next round of rice-growing. The second benefit is that a covering of water protects the young rice plants from frosts and cold that can easily affect the area of the Po valley in the spring. Conversely the water reduces the problem of excessive heat in the summer. A further reason for using flooded fields is that growing rice in dry fields is considered to adversely affect the quality. This area of the Po valley is blessed with an extensive irrigation system and a generous supply of water from the nearby mountains making this type of cultivation possible.

Growing rice with flooding requires very flat fields to ensure an even water depth. Also, a slight difference in height is needed between a water inlet and outlet to ensure a small constant flow through the field so that the water does not stagnate. Levelling large fields is now made easy with laser levelling systems on tractors. The tractors used in rice cultivation have very narrow, spiked metal wheels rather than conventional tires, this allows them to manoeuvre with the least disturbance and sticking in the wet mud.

After fertilisation and correction for soil acidity (flooding fields acidifies the soil) the rice seed is sown, usually in March or April. Each rice seed produces multiple stalks. Traditionally these have been transplanted by hand, accounting for much of the labour the crop required. Modern systems replace this by directly seeding the fields either wet or dry. In non-organic agriculture, herbicides can be used on emerging weeds before the rice seedling come up. This greatly increases the yield in comparison to organically grown rice. Natural systems for reducing weed infestation apart from the use of flooding already mentioned include the use of carp in the water systems. The fish feed on weeds but there is a risk they will eat the rice plants if they run out of weeds, so this is not an ideal solution.

Harvesting, drying and storage
Towards the end of the summer the water is removed from the fields to allow them to dry out. The rice is harvested in September to October using special combine harvesters. The grains will have about 25% humidity which is brought down to around 13% with about 24 hours of drying in warm air dryers. At this level of humidity the rice is stable for storage at 10°C. The rice has to be stored for at least 3 months before milling to allow time for the starch to stabilise/crystallise. Longer resting times are thought to improve the rice’s quality and Tenuta Colombara has made this aspect of the process one of their specialities, ageing all their rice for at least 12 months and also experimenting with longer ageing. The result of this, they believe, is that the rice grains cook more evenly, each rice grain is cooked through at the same time. Whereas normally with rice you either get a properly cooked outer surface with a raw inner or an overcooked outside with a properly cooked inner.

After the resting/ageing the refining process can begin. First the husks are removed using rubber rollers. This leaves whole grain/brown rice which can be cooked and eaten and has better nutritive qualities to white rice due to preservation of proteins, fats, vitamins and fibre which tend to be concentrated in the outer coating of the grain. However, for convenience ,taste preferences and longer shelf-life white rice tends to be preferred, so further processing is done. In the operations that we saw which are fairly small-scale, the outer shell of the grain is ground off in a machine which has a revolving conical stone. The level of grinding can be controlled. Another system used in place of or in addition to this causes grains to rub against each other in order to break off the outer coatings, however, this happens slowly and is therefore very expensive in comparison to other methods. Finally the rice can be put through an optical sorting system to remove non-conforming grains and a grain-size sorter to remove broken pieces.

Par-boiled rice
Another method of rice processing is par-boiling, although this was not used by either of the producers we visited. Production of par-boiled rice involves boiling or steaming the rice before any removal of the grain husks. The rice is then dried and milled either to wholegrain or white rice level. Interestingly, this is not a modern invention, having been practised in Asia for a couple of thousand years. Benefits to this process are that some of the nutrients usually lost in the processing of white rice are retained due to being driven into the centre of the rice grain by the cooking process. Also, the process reduces the glycaemic index of the rice and converts some of the starch to a non-digestible form that acts as a pro-biotic for some beneficial intestinal flora. Finally, the rice is more stable in storage, takes less time to cook, and does not become as sticky while cooking.

Photos of the trip can be seen here

All information for this report came from first hand experience and information given by the people we met at…
Cascina Veneria, Lignana (VC)
Tenuta Colombara, Livorno Ferraris (VC)
Centro Ricerche dell’Ente Nazionale Risi, Castello d’Agogna (PV)


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