Coriander requires a temperate climate and though it can tolerate a warm temperate climate there is a noticeable reduction in yield in this latter case. The concentration of essential oil in the fruits decreases at temperatures above 21°C; the ideal temperature for swelling the grain is a constant 15° to 18°C from the time of seed formation to swelling (Hornok 1986). Though it typically grows in arid regions, it produces well under irrigation.
Very few nutrients are required by this crop. It requires a soil of medium fertility but the best yields are obtained in light and fertile soils. It does not do well in impervious clay soils. Though it is the practice in other countries to fertilize coriander crops, in Argentina this is not customary. Studies have indicated that yield in Argentina responds to the application of up to 90 kg N/ha (Barreyro et al. 1993). No response to P has been observed, though this fact is attributed to the good availability of this element already in the soil (Barreyro et al. 1993). A diminished availability of P in the soil however gives rise to significant increases in yield (Brevedan et al. 1994).
In the cereal growing region coriander is sown between the end of May and the end of July. When sown after this date the plants are less developed and yield decreases. The distance between rows varies between 0.18 and 0.35 m. Sowing is carried out by means of a seed drill, using a seed density of 20 kg fruit/ha. The sowing depth ranges from 2 to 6 cm, depending on the type and humidity of the soil, the quality of the seeds, etc.
During winter the plants remain in the form of rosette plants; with the onset of spring the stems elongate and branch, bearing floral buds. Full bloom is reached after 20 or 30 days and after a further 25 or 30 days the plants begin to mature. Full maturity is reached in the final 25 to 30 days. The total cultivation cycle lasts from 145 to 190 days.
Coriander plants require a total of approximately 400 mm of water during the development cycle, some 100 mm for germination and to last through the winter period, during which they are in the form of rosette plants, and the remaining 300 mm for stem elongation, flowering, and fructification (Lafourcade et al. 1985).
Harvesting can commence when approximately half the fruits on the plant have turned gray. There are a number of inconveniences involved in coriander harvesting, such as the facts that the fruit ripens progressively and the mature seeds are highly susceptible to shattering, exposing them to particular risk under unfavorable meteorological conditions such as rains and strong winds during harvesting time. Harvesting should be carried out in the early morning or late afternoon to prevent seed shattering.
Coriander fruits can be harvested by two methods (Arizio et al. 1994). One is to leave the fruits to completely mature and dry whilst still on the plants, taking 3 to 6 days, harvest them with a windrow and subsequently collect and thresh the cut and dried material. Alternatively, the plants can be harvested directly with or without the application of a desiccant using a wheat combine harvester.
Diseases or pests affecting the cultivation of coriander in Argentina are minimal, and the economic incidence of such effects on production is low. Nevertheless, weeds present a serious problem and can lead to a considerable reduction in yield. The most commonly used herbicide is linuron, which eliminates some grasses and most broadleaf weeds. Trifluralin is also used.
Coriander is cultivated throughout an estimated total of 2840 ha in Argentina, most of this area situated in the humid Pampa (Buenos Aires and southern Santa Fe provinces). Production is around 2500 t/ha, 1500 t of this being sold on the domestic market and the rest being exported mainly to Brasil, the United States, and the United Kingdom (Arizio et al. 1994).
Coriander fruit and the oil obtained therefrom are used in the medicinal, food, and perfume industries. Steam distillation of the coarsely crushed fruit is the most common method used to obtain the volatile oil, with a yield of 0.5% to 1%. Coriander is one of the principle ingredients of curry and of other spice mixtures. In some countries young leaves are used to flavor salads and soups. The green dehydrated parts are used to prepare stock cubes.
There are extensive areas in Argentina where the cultivation of coriander is feasible, one of the most promising being the Lower Valley of the Colorado River in the extreme south of the Province of Buenos Aires. This region, which is under the jurisdiction of CORFO (Corporación de Fomento del Valle del Río Colorado) covers a total of 535,000 ha, 90,000 ha of which are under effective irrigation. According to an extensive report published by SERCOPLAN (Technical Cooperation and Planning Service) (1987), the zone is a productive mosaic characterized by intensive agricultural activities such as horticulture, fruit growing, seed production and the cultivation of cereals, as well as beef production. About 57% of the area under irrigation is dedicated to forage crops, 35% to grain, fruit and forestry, and 8% to horticultural production.
The zone has a semiarid climate with a negative balance, where the annual water deficit is 300 to 500 mm throughout all seasons of the year. The mean annual temperature is 15°C. The first frost is likely to occur in Apr. and the last in Nov., with an average of 43 frosts per year. The soils are not difficult to cultivate and are widely suitable for the traditional crops of the zone. Drainage problems caused by the low permeability of some soils with a clay-texture horizon or with compacted materials which impede the downward seepage of water, together with the presence of brackish water and continuous irrigation, have given rise to a process of salinization over large areas. In an attempt to deal with this problem of a permanent layer of saline water close to the surface, an extensive network of drainage channels has been constructed.
Of the 95% of utilizable land in the area, 90% is actually exploited. The productive structure of the region is characterized by high dispersion in land ownership, inadequate use of soils, and serious problems in commercialization of the produce.
Despite the variety of agricultural and livestock production in the region, the sandy soils and variable salinity levels mean that land use in the area is marginal, irrigation being the only element serving to compensate for the other defects. The irrigation infrastructure comprises a network covering a total of 5,441 km and a drainage network covering 3,738 km. The system as a whole has a catchment capacity of 43 m3/s. The main deficiencies lie in channelling the water at plot level and in the systematization of the soils. A total of 25,000 ha are currently under a systematization project and 2,600 ha are being levelled with laser beams.
Despite the promising potential of the zone in terms of its natural resources and infrastructure, a census carried out in the area shows a low level of demographic growth (0.2% between 1960 and 1980) reflecting stagnating development: low capacity of the region's economy to absorb permanent and temporary labor, and a low level of investment, owing largely to vagaries in commercialization possibilities.
In an attempt to find a solution to this growth problem the above-cited report published by SERCOPLAN (1987) recommends the development of new crops for which there is a more stable demand on both the domestic and foreign markets and whose production process involves a minimum of risk. It is within the framework of this search for solutions to the mentioned problems and recognition of the potential of the region that the idea was put forward of introducing the cultivation of coriander, a crop well suited to the agro-climatic conditions of the area.
The objectives of the present work are to evaluate the relative advantages of different sowing seasons and different row spacings in coriander cultivation in the irrigation zone of the province of Buenos Aires.
Plant height was measured periodically on five plants chosen at random from each plot. At maturity, 10 plants were randomly selected from each plot and the number of umbels per plant counted. The weight of 1000 fruits was determined and the diameter measured of 200 fruits. Lodging was rated visually at maturity on each plot on a scale of 1 (all plants erect) to 5 (³80% of plants severely lodged). Five lineal meters were harvested from the three center rows of each plot in order to calculate yield. Threshing was carried out manually and cleaning done by means of a winnowing machine.
There were 6 planting dates: the first (1) and the second (2) fortnight of July, the first (3) and the second (4) fortnight of Aug., and the first (5) and the second (6) fortnight of Sept. Treatments were replicated five times in a completely randomized design. Individual plots consisted of 17 rows, 6 m long.
There were four treatments, consisting in rows set 0.15, 0.30, 0.45, or 0.70 m apart. Treatments were replicated four times in a randomized complete block design. Individual plots were 6 m long and the number of rows varied according to the spacing, keeping the total plot area constant for all treatments, approximately 17 m2.
Late sowing also caused a reduction in plant height (Table 1). There was no lodging. Fruit size was larger in plants sown during the first three dates than in those sown during the last three, and early sowing produced a larger number of umbels per plant and a higher yield.
An analysis of the results of different row spacings showed that the height and number of plants per unit area was similar (Table 2). With greater row spacing, 0.70 m, the lodging rate was high; at 0.45 m the percentage of lodged plants was low and at 0.30 m and 0.15 m it was zero.
The number of umbels per plant was significantly higher with a row spacing of 0.70 m than with spacings of 0.15 and 0.30 m (Table 2). There was no significant difference in the diameter and weight of the fruit nor in the yields obtained with the three closest row spacings, though there was a reduction in yield at distances greater than 35% with respect to the average spacing. These results for the most part coincide with those reported by Rubió et al. (1986), who also found no difference between the yields of the three closest spacings. However, Rubió et al. (1987, 1992) reported higher yield with narrower spacing.
The results obtained indicate the benefits of early sowing for obtaining higher yield, showing this increase in yield to be due mainly to an increase in the number of fruits per plant. The best yields are obtained with narrowly spaced rows.
Current economic conditions favor the introduction of new crops into the irrigated areas of Argentina. Among such new crops, coriander has shown particular promise. The Lower Colorado River Valley (39° 23' S, 62°37' W) covers an area of more than 500,000 ha, 90,000 ha of which are under effective irrigation.
The sowing of coriander in the Lower Colorado River Valley can be carried out from autumn to the end of winter and even up to spring. In this area the greatest yields are obtained from seeds sown at the beginning of winter. Late sowing leads to a progressive and significant decline in yield. The later sowing takes place, the shorter the total growth cycle, which can vary from 170 to 100 days. The number of umbels per plant and the weight of 1000 fruits were found to be higher in early-sown plants. Seeds sown in narrowly spaced rows (up to 45 cm) gave higher yields (35%) than those sown in widely spaced rows.
|Planting date||Initial bloom (days)||Maturity (days)||Height (cm)||Umbels per plant||1000 fruit wt (g)||Yield (kg/ha)|
|1||(July 1 to 15)||100||170||0.68az||12.5a||12.1a||1731a|
|2||(July 16 to 31)||87||153||0.64a||12.1a||12.1a||1415b|
|3||(Aug. 1 to 15)||77||142||0.66a||11.7a||12.3a||1495b|
|4||(Aug. 16 to 31)||59||122||0.59a||10.0b||11.7b||1032c|
|5||(Sept. 1 to 15)||55||118||0.63a||9.7b||11.8b||853cd|
|6||(Sept. 16 to 30)||42||100||0.53a||8.8c||11.8b||805d|
|Row width (m)||Plants/m2||Height (m)||Lodging score||Umbels/plant||1000 fruit wt (g)||Yield (kg/ha)|