Ideal substrate for arugula cultivation

Arugula plants develop well in lower temperature conditions, soils with sufficient organic matter and water available throughout vegetative growth. But the crop does not grow in waterlogged soil, so appropriate locations must be prepared for planting. Sowing can be done directly in the soil or in specific trays for seedling production and then transferred to the beds. Harvesting is done 30 days to 50 days after sowing, when the oldest leaves are removed or by cutting the plants, around 2cm above the ground for reuse. (Filgueira, 2000).

Production is more concentrated in the South and Southeast regions of the country. Although sowing is possible all year round, its development is favored by lower temperature conditions. The high temperature causes the plant to anticipate the reproductive phase, emitting the floral tassel prematurely, and as a consequence, its leaves become hardened and spicier (Filgueira, 2000). In addition to the quality of the seedlings, the vegetable producer always seeks to reduce the costs of his activity. To make this possible, work is being carried out in Brazil with the aim of taking advantage of materials available in planting regions, to acquire the substrate for the formation of vegetable seedlings and reduce the share of commercial fertilizers, which do not always have the necessary substrates, and as a consequence, causes nutritional problems in seedlings (Silva et al.

This work aimed to observe, over a period of approximately 30 days, the development of the vegetable Eruca sativa (arugula), observing its growth in four different types of soil samples: sand, clay, earthworm humus and a mixture of the three soils in equal parts.

The experiment

      The experiment was conducted in João Pessoa, Paraíba, from February 14 to March 12, 2010. To compose the experimental unit (average of 1kg of soil sample per pot), four soil samples were used: the first with construction clay, the second with sand, the third with earthworm humus and the fourth with a mixture of the previous three in equal proportions. The samples were placed in jars that hold 1kg of substrate, of the same size, with holes in the bottom for water to escape. Soil samples were used for the chosen vegetable species, thus, in total, four containers, numbered from 1 to 4.

      Next, holes approximately 1cm deep were made and eight seeds were deposited in each hole, then lightly closing them with the sample from each container, on February 14, 2010, at 17 pm. The pots were placed in an airy place, watered once a day with 50ml of water, in the late afternoon, exposed to the sun in the morning and in the shade for the rest of the day. The containers were marked and every day the plants were measured and their data recorded.

 Results

         After two days, the first results were obtained for Eruca sativa (arugula): in the morning the first sprouts appeared in the containers with earthworm humus and mixture. In the afternoon the first sprouts appeared in the container containing sand, smaller in size than in the other two containers containing humus and the mixture. Finally, the container with the clay yielded no results. One week after sowing, four samples were taken from each container in which there was leaf development, thus leaving four samples in each container, except for the clay, which until now had not shown any type of development. It is noted, firstly, that the samples grown in humus resulted in a stronger color (dark green), appearing to be more developed than those in the other containers. In the soil mixture, a yellowish-green sample was obtained, with development slightly less than humus. In the sand, the samples showed the lowest development of all, with smaller leaves and little growth.

      After two weeks of observation, the characteristics of the samples changed significantly. In the humus and in the mixture, the color remained the same, presenting a dark green tone in both types of soil, but, in the mixture, contrary to information from a week ago, the samples were much more developed than in the humus, especially when it comes to the size of the leaves. In the sample with sand, the development was very small, with barely noticeable growth as the days went by.

A good soil provides sufficient water retention for germination, in addition to enabling the emergence of seedlings, also having attributes of good aeration to allow the passage of oxygen, which is flexible to root penetration and good resistance in relation to the plant's fixation. Furthermore, it must offer aggregation and transport, absence of harmful microorganisms, richness in essential substrates, adequate pH, light-medium texture and stable structure for development (Silva et al, 2000). This information may explain why the samples in the container with the soil mixture developed better over time; because, in this mixture, the clay, as it aggregates more easily, guarantees resistance, the sand allows good aeration and the humus is a source of some nutrients needed by the plant. It is also verified why it did not germinate in the clay container. In contact with water, the soil became increasingly compacted, preventing oxygenation. The substrate must have physical, chemical and biological characteristics necessary to allow full growth of the species produced (Setubal & A. Neto. 2000). Therefore, in a container with only sand, it will be very difficult for some species that require certain components to develop, as the sand is poor in nutrients.    

 The quality of the substrate used in seedling production is extremely important in the initial growth and development of the plant and in qualifying its productive potential. This fact is justified because when producing seedlings inside a container, root growth and nutrient absorption, unlike what occurs in the soil, are restricted to the amount of substrate contained inside the container used. For this reason, the chemical composition of the substrate must include nutrients capable of promoting the supply of substances to the plant, without causing a deficiency of any element necessary for its growth (Moreira, 2005). However, it can be observed that even without replacing the nutrients in the containers with humus and mixture, the development of the arugula was not affected, based on the harvest within 45 days after planting, with the arugula measuring approximately 14cm to 18cm, the results obtained in 27 days, were samples measuring between 10cm and 11cm (Table 1).

 

Table 1 - Summary of arugula growth from February 14 to March 12, 2010

 

SUBSTRATE	DAY / SIZE	DAY / SIZE	DAY / SIZE
MUD SAND HUMUS MIXTURE	26/02/10 _ 0 cm 26/02/10 _ 1 cm 26/02/10 _ 3 cm 26/02/10 _ 3 cm	05/03/10 _ 0 cm 05/03/10 _ 2 cm 05/03/10 _ 6,5 cm 05/03/10 _ 7 cm	12/03/10 _ 0 cm 12/03/10 _ 3,2 cm 12/03/10 _ 10 cm 12/03/10 _ 11,2 cm

SUBSTRATE

DAY / SIZE

DAY / SIZE

DAY / SIZE

MUD

SAND

HUMUS

MIXTURE

 

26/02/10 _ 0 cm

26/02/10 _ 1 cm

26/02/10 _ 3 cm

26/02/10 _ 3 cm

05/03/10 _ 0 cm

05/03/10 _ 2 cm

05/03/10 _ 6,5 cm

05/03/10 _ 7 cm

12/03/10 _ 0 cm

12/03/10 _ 3,2 cm

12/03/10 _ 10 cm

12/03/10 _ 11,2 cm  

According to Camargo (1992), at high temperatures plants can become more hardened, in addition to having a stronger aroma and flavor and developing prematurely. This explains the fact that the arugula germinated in two days after planting, at this time of year when the temperature is higher, knowing that, in mild temperatures, its germination takes around four to seven days.

After the results obtained, it is possible to state that Eruca sativa (arugula), in relation to the various soil samples submitted, showed greater development in the container with the mixture of the three soils, which provided the best growth for the plant, due to its good structure, aeration and nutrients present. In relation to the container with humus, there was good development, but it ended up being affected by the lack of structure acquired in the previous container due to the presence of clay (which allows for greater water retention, essential for the plant's growth).

 

Box

The arugula

A Eruca sativa (arugula), also known as Persian mustard, is a vegetable originating from regions close to the Mediterranean. It belongs to the cruciferous family, the same as turnips, cabbage, etc. Its  leaves are elongated and grow around 10cm to 15cm in height. The leaf is the consumable part of the plant; It has a light green to dark green color with long, well-shaped leaves with a spicy flavor. It is rich in vitamins A and C, as well as minerals such as calcium, iron, sulfur and potassium and omega 3.

 

 Click here to read the article in Revista Cultivar Hortaliças e Frutas, issue 77.