Rice, a key crop for agriculture

Rice (Oryza sativa) is a single-celled plant, normally annual, from the Poaceae (Gramineae) family. We farmers grow the Oryza grass species to harvest the seeds (rice) for consumption. More often than not, rice is an annual plant; however, in very rare cases, the rice plant is grown as a perennial plant and can live for 10 years or more. The biological cycle of annual rice (days from sowing to harvesting) ranges from 95 days for very early varieties to almost 250 days for very late varieties. Medium-ripening varieties can be harvested 120–150 days after sowing.

 

The rice plant is composed of roots, a stem, leaves and panicles. The length of the plant’s root system can range from 25 to more than 100 cm. The rice seed is often referred to as the grain. When the panicles mature, they typically contain 50 or 60 to more than 120 grains per rice plant. The grain structure has three layers:

• Husk
• Bran layer
• Endosperm, containing the embryo.

 

Rice is the second most widely consumed cereal in the world. Its production is geographically concentrated, with more than 85% coming from Asia. Just seven Asian countries – China, India, Indonesia, Bangladesh, Vietnam, Myanmar and Thailand – produce and consume 80% of the world’s rice. It is grown commercially in more than 110 countries. The top five producing countries are China, India, Indonesia, Bangladesh and Vietnam. By contrast, the top five rice-exporting countries are India, Thailand, the United States, Pakistan and Vietnam. Alongside Asia and the United States, rice is also commercially grown to great success in countries of the Mediterranean (Italy, Morocco and Greece), Latin America (Uruguay, Paraguay, Brazil and Argentina) and in Central Europe (Belgium and the Netherlands).

 

Spain, meanwhile, ranks as the eighteenth global exporter with 0.7% of the world’s exports. Of the total, 83% of Spanish rice is exported to the EU (mainly the UK, Belgium, the Netherlands and France). By variety, Spain mainly trades in Indica (long-grain) rice, which makes up 58% of total exports.

 

The world rice market has distinctive characteristics that make the volatility of its prices commonplace. There are two aspects of the global rice market to note:

 

1. Small changes in the production or consumption of any of the major producers, consumers, sellers or buyers, can have a major impact on volume in the market and, consequently, on price.
2. Concentration is high among rice exporters around the world. Of the total, 85% of exports are from 7–9 countries, so supply changes, due to weather, for example, have severe repercussions for prices.

 

Origins

Rice cultivation began nearly 10,000 years ago, in many of the wet regions of tropical and subtropical Asia. It is thought that India may have been the first country to grow rice, due to the abundance of wild rice there. But it was in China where cultivation was developed, from its lowlands up to its highlands. Rice was introduced from Asia to other parts of the world by several likely routes.

 

Economic importance

Rice is the staple food of more than half the world’s population. Nonetheless, considering the extent of the area used to cultivate it and the number of people who depend on its harvest, it is the most important food worldwide. Besides its importance as food, rice provides employment for the largest sector of the rural population in most of Asia, since it is the everyday cereal of South and East Asia, although it is also widely grown in Africa and the Americas and both extensively and intensively in parts of southern Europe, especially in the Mediterranean regions.

The consumption of rice – and, hence, its trade – is differentiated by rice type and quality. The types are as follows:

–Indica long-grain: This type of rice accounts for 85% of the world’s rice trade and includes approximately 10–15% aromatic rice (jasmine, basmati, etc.), 35–40% high-quality rice (less than 10% broken grains) and 30–35% low-quality rice.

–Japanese medium- and short-grain: the trade in this type of rice accounts for a smaller 15% share.

 

Temperature, soil, climate and other factors

The ideal temperature for rice is between 30 and 35°C and it needs a minimum of 10 to 13°C to germinate. The growth of the stem, leaves and roots requires a minimum of 7ºC, with 23ºC considered optimal. At temperatures above this, the plants grow faster but their tissues become too soft, making them more susceptible to disease. Panicle development is influenced by temperature and the shortening of the days.

The panicle, which we farmers usually refer to as the espiga, or bolt, starts to form about thirty days before it appears and just seven days after beginning to form, it has already reached about 2 mm. Then, 15 days before the panicle appears, it develops very quickly – during this period, it is at its most sensitive to adverse environmental conditions.

Rice can be grown in a wide range of soils with textures ranging from sandy to clay. It is usually grown in fine and medium-textured soils, typical of the sedimentation process of extensive, flooded plains and river deltas. Fine-textured soils make for hard work, but they are more fertile because of their higher clay content and organic matter, and because they provide more nutrients. Soil texture is therefore an important factor in irrigation and fertiliser management.

 

Harvesting

The best time for harvesting is when the panicle reaches physiological maturity (when 95% of the grains are straw-coloured and the remainder are yellowish) and the moisture content of the grain is 20–27%. Mechanised harvesting using a tracked harvester is recommended.

To obtain a high price for our rice, we need to focus on the percentage of whole grains out of the harvest total. This value chiefly depends on the variety, but also varies according to the point of harvesting: if the rice is harvested very immature, the handling period in the dryer increases, which lowers this percentage. After threshing, the rice may be 25 to 30% wet, so it must be dried to obtain a moisture level below 14%.

 

Rice fertiliser

There are many factors and possibilities to consider when choosing a fertiliser for rice. For example, the amount of fertiliser required for every hectare of rice will depend on the type of soil.

This article focuses on NPK as the fertiliser to use in rice fields:

Nitrogen: most of the nitrogen found in soil is in organic forms, making up part of the organic matter and harvest residues, but the rice plant can only absorb nitrogen from solutions in inorganic form. The conversion of nitrogen from organic to inorganic takes place through the mineralisation of organic matter, and the end-products of this process will differ according to the soil conditions.

Nitrogen is considered to be the nutritional element with the most direct impact on production because it increases the percentage of filled spikelets, increases leaf surface and helps increase grain quality. Rice needs nitrogen at two critical times of its growth:

 

1. During the medium tillering phase (35–45 days after sowing), when the plants are developing the vegetation needed to produce rice.

2. From the beginning of the upper internode elongation until this internode reaches 1.5–2 cm.

Nitrogen should be given in two phases: as a basal dressing, and at the start of the reproductive cycle. The dose depends on variety, soil type, climate conditions, fertiliser management, etc. In general, the dose is 150 kg of nitrogen per hectare in two distributions (75% as a basal dressing, 25% at the panicle initiation stage).

Ammonium fertilisers should be used as the basal dressing and dug in to a depth of about 10 cm, prior to flooding, with use of ploughing and levelling. The top dressing should be applied at the panicle initiation stage, using ammonium nitrate. The nitrogen fertilisers used are generally ammonium sulphate, urea or complex fertilisers containing other nutritional elements besides nitrogen.

Phosphorus: also increases rice production, though its effects are lower than those of nitrogen. Phosphorus stimulates root development, promotes tillering, contributes to early and uniform flowering and ripening, and improves grain quality.
Rice needs phosphorus in the early stages of its development, so phosphorus fertiliser is recommended as a basal dressing. The amount of phosphorus to be applied ranges from 50 to 80 kg of P2O5/ha. The first figure is recommended for clay loam soil, while the second is for loose, light soil.

Potassium. Potassium increases resistance to lodging, disease and unfavourable weather conditions. Potassium is absorbed similarly to nitrogen during the crop cycle. The potassium dose will range from 80–150 kg K2O/ha. The higher figures are used on loose soils and when high doses of nitrogen are used.

At DFINNOVA, you will find a team of qualified specialists to help you manage your crops with our wide range of technological solutions, including complete nutrition and biostimulation programmes, for maximum yield.

Reach out to us, we are here to support you and are always happy to help.