Chapter 5

Use of fertilizers by crop and region

The agricultural production regions may be divided into:

1. The Pampa, comprising twelve subregions. The grain crops are grown mainly in this area (Table 7).

2. The regional economies:

• NEA (Northeast)

• NOA (Northwest)

• Cuyo and Comahue

TABLE 7
Sown area, proportion fertilized and average rates, 2002/03

* Including brewing barley
** Permanent pastures

TABLE 8
Fertilizer consumption, 2002/03 ('000 tonnes)

The groups of crops grown in this area are industrial crops; fruit and horticultural crops; and vines.

The fertilizer consumption is given in Table 8.

Argentina is at present the third largest exporter of soybeans and of maize in the world and the fourth largest exporter of wheat.

Whereas almost 90 percent of wheat producers now fertilize their crops, in 1993 only 28 percent of wheat farmers did so. Seventy two percent of maize farmers currently fertilize their crops, a six-fold increase since 1993.

Pampa

The main developments in the 1990s were the increase in the use of fertilizers (Figure 8) and direct seeding. Since the introduction of direct seeding, urea and DAP have been the most used fertilizers (Table 9). More recently, with the recognition of the impact of sulphur on yields, the application of mixtures containing ammonium sulphate or potassium and magnesium sulphate has increased. Field trials have not yet shown a response to potash in the region.

Phosphate fertilizers or phosphate fertilizers mixed with sulphur products are generally applied at seeding, in rows or banded, using appropriate machines. The nitrogen fertilizers are applied in different ways according to the crop and region. In the case of urea, about 45 percent is applied at seeding on wheat and 28 percent on maize, the remainder being top-dressed.

Sorghum and groundnuts are not normally fertilized, nor, in descending order of area, are flax, rye and rape.

TABLE 9
Pampa. Average rates of application of urea, DAP and blends in the Pampa

The irrigated area devoted to cereal production is very small, and concerns mainly maize. In these areas, the rates of nitrogen may be about 30 percent higher than in dry land areas.

Cereals

It was on wheat that farmers first observed the advantages of fertilization, probably because most information was available for this crop. Next maize followed. Since wheat and maize are grown in most parts of the Pampa region, other crops in the rotation began to be fertilized. Pastures, especially temporary pastures, were the third sector to be fertilized. Lastly the oil crops, particularly sunflower and soybeans, were fertilized. The response of these crops to fertilizers is less apparent, mainly in the case of soybeans.

TABLE 10
Percentage of farmers using fertilizers on different Pampa's crops

Today cereals, principally wheat and maize, account for almost 60 percent of fertilizer consumption. If oil seed crops and pastures are included the proportion is 80 percent (Table 10).

There are large variations in fertilization within and between regions. The soils of the Pampa region are not uniform; also some crops are grown in areas where water is the main limiting factor.

The response to the application of nitrogen on wheat has been studied intensively and varies between 10 kg and 20 kg of wheat per kg of N applied according to the soil moisture and nitrogen conditions, and also soil and applied phosphorous. At the usual rates of application between 50 and 70 kg/ha of N, responses of between 500 and 1 400 kg/ha can be expected. On maize, the crop most studied after wheat, trials indicate responses of 12 and 30 kg of grain per kg of N applied. The responses depend on many more variables than the level of nutrient in the soil, in particular the water availability, the genetic potential and the sowing rate. For the usual rates of 70 to 80 kg/ha of N applied as urea, increases of yield between 800 and 2 500 kg of maize can be expected. The rates associated with the most profitable response of sunflower are much less, about 40 kg/ha N. Higher rates, up to 80 kg/ha N, result in economic responses only in some years. The increases in yield observed in a network of 93 trials are 12 percent on average with an average efficiency of 4 kg of grain per kg N (Diaz Zorita, 2003).

Source: Berdardo, 1994.
*Response from the application of 100 kg/ha of ammonium phosphate.

The responses to phosphate depend on the level of soil phosphate. In the case of wheat (Figure 9), for the region of southeast Buenos Aires, the relationship is 70 kg of wheat for each reduction of one ppm of available soil P (Berdardo, 1994). These relationships do not differ from those experienced in the northern Pampa region, where the economic optimum rate for a wheat: P₂O₅ relationship of eight, varies according to the equation P₂O₅ = -11 +286/ppm P (Senigagliesi et al., 1983). In the case of maize, the expected response varies between 12 and 20 kg per kg of P2O5 applied (Darwich, 1991). For soybeans, according to the results of a network of 50 trials in the northern Pampa region, the response increases by 50 kg/ha for each ppm of P below 16 ppm. Above 16 ppm there is no response. Hence, a response of about 200 kg/ha can be expected on soils with 12 ppm P (INTA, 2002).

There is often a response to sulphur in the northern Pampa region but a response is rare in the south, due to the higher organic matter content in the soils. An attempt has been made to obtain a correlation with sulphur levels at seeding but the results are erratic and prediction is difficult. Increasingly, physical mixtures with fertilizers containing sulphur are applied. In general the response with average applications between 5 and 20 kg/ha S as sulphate is between 200 to 500 kg/ha for wheat and soybeans, and between 400 to 700 kg/ha for maize.

TABLE 11
Non-Pampa regions: Fertilizer consumption, 2002/03 (‘000 tonnes of product)

Economic regions

Industrial crops and horticultural crops produced in the regional economies are often grown on soils that are low in nutrients and organic matter, unlike the Pampa soils, and which therefore need to be fertilized in order to maintain yields. Fertilizers were applied in these areas long before they were applied on the Pampa soils (Table 11).

The areas of some of these crops suffer periodically from large variations. Cotton and rice are exported principally to Brazil and depend on the demand from this country, which fell with the devaluation of the Real. Whereas one million ha were sown to cotton in 1997, today the area is 50 000 ha. Similarly the rice area fell from 290 000 ha to 126 000 ha between 1998 and 2001. Sugar cane continues to be by far the most important agricultural activity but its predominance is decreasing. A substantial area of sugar cane in Tucumán was replaced by the successful introduction of lemons. Tariffs were removed during the harmonization of MERCOSUR policies, favouring the importation of sugar from Brazil. The international competitiveness of tobacco was affected by the high exchange rate until 2001, and as it was unable to compete on the international market as effectively as Brazil its area has fallen from 50 000 ha in 1997 to 30 000 ha.

Industrial crops

Tobacco, sugar cane and cotton depend increasingly on the industrial sector, which controls production through prices and purchasing policies, depending on their needs. In the case of tobacco, two multinational tobacco companies and the cooperatives are the purchasers. The number of sugar factories has fallen and they have increased their own sugar cane production, changing into large oligopolistic purchasers.

Tobacco

From a fertilizer point of view, the main fertilizer market for tobacco is in the northern regions of Argentina. Almost all the inputs are supplied and payments recovered by cooperatives or large tobacco companies. There is a price stabilization scheme administered by the State through the Special Tobacco Fund (FET). The Secretary for Agriculture has the authority for application of FET and has the power to fix the price of different varieties of tobacco and to transfer 80 percent of the receipts to the provinces to enable them to pay the producers. As with other crops, the competitivity of tobacco production was affected by a high exchange rate when the peso rate was fixed to that of the dollar.

The fertilizers applied to tobacco are generally mixtures and specialties, rather than commodity fertilizers. The crop requires high rates of fertilization, between 500 and 800 kg/ha, with chloride-free potash and a high proportion of nitrate nitrogen.

Cotton

In NEA, Chaco, Formosa and north of Santa Fe, very few producers fertilize cotton, mainly because the soils are rich in phosphorus and potassium, although not in nitrogen. Producers in the cotton area of Corrientes are smallholders who apply little fertilizer. The traditional varieties suited to manual cultivation are not very responsive to fertilization, although there is evidence that moderate applications of nitrogen may give an economic response. However, the new varieties, especially the transgenic varieties, respond to fertilization. The extension of mechanical harvesting and the planting of varieties suited to this operation also have a large influence.

In NOA there are some irrigated areas of cotton that are fertilized. Little fertilizer is applied to cotton in the non-irrigated areas.

Sugar cane

The sugar cane area in NOA was one of the earliest markets for fertilizers, together with citrus on the littoral. The sugar factory is the sole buyer and is involved in several commercial activities, including the supply of inputs. There are differences between the very large plantations, with strong negotiating power and owning large areas of sugar cane, and the smaller sugar factories whose supply of sugar cane depends on a large number of small producers.

Trials in the 1970s showed no response to phosphate and potash. However, trials during the past five years have demonstrated that there are many soils that are deficient in phosphate and a few are deficient in potash.

Fruit crops

There is a great variation in the profitability of fertilization of fruit crops, depending on the product, the extent of competition, i.e. the price, and the involvement of the agro-industrial sector. Exchange rate fluctuations in recent years have affected these crops, according to whether they were destined for export or the domestic market. Fertilization also varies considerably between regions.

The main fruit growing areas are in the region of Cuyo (Mendoza, San Juan and La Roja). Fruit production is important in Alto Valle (Rio Negro and Neuquén). In both areas fruit production is coordinated by agro-industry and exporters.

In the citrus area of Tucumán, only 8 000 ha are irrigated, 70 percent by micro spraying (under pressure), 20 percent by drip irrigation and 10 percent by under-tree spraying. Fertigation is not common. Fertilizer mixtures are often applied in the early years of the crop, after which only urea is applied. The use of fertigation is much more frequent in Salta. The main growing season for oranges is in winter, which is normally dry and justifies fertigation.

Fertilization in NEA has been neglected in recent years for economic reasons. The sandy soils are often deficient in micronutrients. Irrigation is less common than in NOA.

The banana crop is normally fertilized with urea and potassium chloride at rates of 500 to 600 kg/ha. The area of banana in Tucumán has increased substantially, using a high level of technology that includes fertigation.

The deciduous fruit sector is not attractive for the fertilizer market. In the Cuyo region the growing of deciduous fruits is often a secondary activity of the vine grower.

Vines

Argentina ranks number seven in the world production of wine. The fertilization of vines varies according to whether the crop is for table wines, fine wines or table grapes. Normally in the case of fine wines, quantity is sacrificed in the interests of quality. In the fine wine area of Mendoza, about 15 percent of the crop is drip-irrigated and fertilized at a rate of 300 kg/ha with specialty products. In San Juan about 40 percent is irrigated. However, despite the substantial increase of fertigation in recent years, most fertilization is by traditional methods. Traditional fertilization involves 150 to 250 kg/ha of urea and 100 kg/ha DAP, MAP or TSP. A traditional practice under traditional irrigation is to apply 20 t/ha of goat or poultry manure to improve the structure of the soil.

Yerba mate

In recent years there has been a substantial fall in the production of yerba mate and less than three percent of the area is fertilized.

Tea

In recent years there has been a substantial recovery of tea production, with the reactivation of old plantations. However, only a small area is fertilized and there is a large potential market for this crop.

Rice

In Corrientes, all the rice is irrigated. Fertilizer mixtures and NPK compound fertilizers are applied, since there is an acute soil deficiency of phosphate and potash. The application of urea before flooding is recommended but few producers are organized to do this and many top-dress before flowering, which is only possible by airplane. In general this results in low efficiency and large losses by volatilization. In Entre Rios, normally moderate rates of urea are applied, often by airplane.

Beans

This is a traditional crop in NOA, although in recent years it has been substantially replaced by soybeans. It is a low cost crop, which is rarely fertilized. In spite of being a leguminous crop, it responds to nitrogen since the rhizobia are inefficient. Micronutrient deficiencies are often observed and foliar fertilizers are sometimes applied.

Horticultural crops

All horticultural crops are fertilized, often using high rates of fertilization, perhaps 700 kg/ha, in addition to manure or compost. In some areas the crops are grown under polyethylene tunnels, with drip irrigation and fertigation. The area planted with potatoes in Tucumán has increased from 6 000 to 10 000 ha. Potatoes are also very important in the Pampa region. Fertilizer application is 300 kg/ha DAP and 100 kg/ha urea.