Fitociencia

 

Productive performance of carrot and rocket cultivars in strip–intercropping system and sole crops

 

Comportamiento productivo de cultivares de zanahoria y achicoria con un sistema de intercultivo en surcos y cultivos únicos

 

J. Suerda Silva–de Lima¹*, Francisco Bezerra–Neto¹, María Zuleide–de Negreiro¹, M. Clarete Cardoso–Ribeiro¹, Aurélio P. Barros–Júnior²

 

¹ Graduate Program in Plant Science, Universidade Federal Rural do Semi–Árido (UFERSA), Mossoró, RN, Brazil. P. O. Box 137. 59625–900. *Author for correspondence: (jailmaagro@gmail.com), (bezerra@ufersa.edu.br), (zuleide@ufersa.edu.br), (clarete@ufersa.edu.br).

² Universidade Federal Rural de Pernambuco/UAS, Serra Talhada –PE, Brazil (aureliojr02@yahoo.com.br).

 

Recibido: Marzo, 2009.
Aprobado: Octubre, 2009.

 

ABSTRACT

A great challenge for the success of intercropping systems is the ability in determining which species should be used and, especially, the management of the cultivars or varieties to be associated. The objective of the present research was to evaluate the effect of the association of two cultivars of carrot (Daucus carota L.) with two cultivars of rocket (Eruca sativa M.) in two crops in strip–intercropping system and sole crops on the productive performance of these vegetables. The experimental design was randomized complete blocks in a 2×2+2 factorial with five replications. Treatments were the association of two carrot cultivars (Brasília and Esplanada) with two rocket cultivars (Cultivada and Folha Larga) plus two additional treatments (two carrot cultivars or two rocket cultivars as sole crops in each block). The major results were: the rocket cultivars Cultivada and Folha Larga showed similar (p>0.05) productive performances in sole crop and intercropping system. The best performance (p<0.05) of the rocket was observed in the second cultivation. The carrot cultivar Brasília showed the best productive performance (p<0.05) in both sole crop and intercropping system. The intercropped systems of carrot Brasília + rocket Cultivada and carrot Brasília + rocket Folha Larga were the best association based on agri–economic efficiency.

Key words: Daucus carota, Eruca sativa, agronomic and economic efficiency.

 

RESUMEN

Un gran desafío para el éxito de los sistemas de intercultivo es la capacidad de determinar cuáles son las especies que deben utilizarse y, específicamente, el manejo de los cultivares o variedades a asociarse. El objetivo de esta investigación fue evaluar el efecto de la asociación de dos cultivares de zanahoria (Daucus carota L.) con dos cultivares de achicoria (Eura sativa M.), en dos cultivos con sistema de intercultivo en surcos y de cultivos únicos, sobre el comportamiento productivo de estas hortalizas. El diseño experimental fue de bloques completos al azar con un arreglo factorial 2×2+2 con cinco repeticiones. Los tratamientos fueron la asociación de dos cultivares de zanahoria (Brasília y Esplanada) con dos cultivares de achicoria (Cultivada y Fogha Larga) más dos tratamientos adicionales (dos cultivares de zanahoria o dos de achicoria como cultivos únicos en cada bloque). Los resultados principales fueron: los cultivares de achicoria Cultivada y Folha Larga tuvieron comportamientos productivos similares (p>0.05) como cultivo único y en sistema de intercultivo. El mejor comportamiento (p<0.05) de la achicoria se registró en el segundo cultivo. El cultivo de zanahoria Brasília mostró el mejor comportamiento productivo en cultivo único y en sistema de intercultivo (p< 0.05). Los sistemas de intercultivo de zanahoria Brasília + achicoria Cultivada y zanahoria Brasília + achicoria Folha Larga fueron la mejor asociación con base en la eficiencia agroeconómica.

Palabras clave: Daucus carota, Eruca sativa, eficiencia agronómica y económica.

 

INTRODUCTION

The intercropping is used in the farming systems in the semi–arid region of northeastern Brazil. Besides, due to biological, nutritional, economic and social reasons, it is an alternative for improving food production and income under culture conditions where resources are limited. Although, it is a widely used practice, there are still challenges with regard to the type of crop to be used in intercropping, as well as its management, especially in systems involving vegetables.

In the semi–arid region of the state of Rio Grande do Norte, the production of vegetables is growing and part of this production comes from intercropping systems of carrot (Daucus carota L.) and lettuce (Lactuca sativa L.), carrot and green coriander (Coriandrum sativum L.), and recently carrot and rocket, among other vegetables (Oliveira et al., 2004; Freitas et al., 2009). In these associations the leafy vegetables are grown twice during the cycle of carrot, one simultaneously with carrot and the other in the penultimate week before the harvest of carrot. Research with rocket cultivars in northeastern Brazil is just beginning, both as sole crop and intercropping system. Thus, rocket Cultivada showed the best agronomic performance in the second planting time (June to October) in the spacing of 0.20 m×0.05 m (Freitas et al., 2009). This crop is rich in vitamin C, potassium, sulfur and iron, besides being anti–inflammatory and detoxifying (Trani and Passos, 1998), whereas carrot contains sodium, calcium, magnesium, potassium, iron, phosphorus, nitrogen, and high levels of carotene.

Since there are new carrot and rocket cultivars for the semi–arid region of northeastern Brazil, it is essential to obtain comparative data on the productivity of materials in intercropping systems. This region is characterized by high temperature (25 °C to 38 °C), high solar radiation (a little over 12 h d^–1), relative humidity (RH) around 50 % and rainfall between 400 to 800 mm year. The intercropping system is a technology that could provide an increase in productivity per unit area and a diversified production of food in the same area, generating better temporal distribution of income, an increase of vegetative protection of soil against erosion, and better control of weeds as compared with the sole cropping system, due to a high density of plants per unit area (Heredia Zarate et al., 2003), reduction of risk of total crop losses and better use of family labor and resources of the environment.

Between intercropping systems of carrot and lettuce under high temperature and high solar radiation, there were no significant differences, and lettuce in sole crop (Negreiros et al., 2002). Oliveira et al. (2004) evaluated the association of lettuce cultivars of the crispleaf (Elba, Lucy Brown, Tainá and Verônica) and looseleaf group (Babá de Verão, Maravilha das Quatro Estações, Elisa and Carolina) with carrot cultivars (Alvorada and Brasília), in two crops in alternate strips (two strips of carrot and two strips of lettuce, with four rows of each), and their findings were: 1) no significant interaction between the cultivars of vegetables in the two seasons of cultivation; 2) the intercropping systems of Alvorada carrot and Lucy Brown lettuce and Brasília carrot and Maravilha das Quatro Estações lettuce were better with LER (land equivalent ratio) of 2.16 and 2.15 and return rates of 2.05 and 2.33.

The objective of our study was to evaluate the effect of the association of two cultivars of carrot with two cultivars of rocket in two crops in strip–intercropping system and sole crops on the productive performance of these vegetables, as well as to look for cultivars association that provide good interspecific combining ability and better yield and agri–economic efficiency.

 

MATERIALS Y METODS

This study was conducted in the vegetable garden of the Plant Sciences Department of the Universidade Federal Rural do Semi–Árido (UFERSA), in Mossoró, RN, from June to October 2006, at 5° 11' S, 37° 20' W and 18 m of altitude. The climate of the region according to Thornthwaite, is semi–arid and according to Köppen is Bswh', dry and very hot, with a dry season (June to January) and a rainfall season (February to May). During this research the mean daytime temperature was 28.2 °C, daily sunshine 12 h and 50 % RH. The soil was classified as a Eutrophic Yellow–Red Ultisols (EMBRAPA, 1999). Samples were taken in the experimental area and mixed in order to obtain a composite sample, which was analyzed at the Chemistry and Fertility of Soils Laboratory of the UFERSA: pH (soil:water ratio 1:2,5) 7.90 (alkaline soil); Ca 5.80 cmol_c dm^–3; Mg 1.00 cmol_c dm^–3; K 0.40 cmol_cdm^–3; Na 2.06 cmol_cdm^–3; Al 0.00 cmol_c dm^–3; P 18.4 mg dm^–3 and N 6 g kg^–1. Therefore, the soil has a medium fertility with low level of P and N.

The experimental design was a complete randomized block with five replicates and a 2×2+2 factorial arrangement of treatments: two carrot cultivars (Brasília and Esplanada) and two rocket cultivars (Cultivada and Folha Larga), plus two additional treatments (two carrot cultivars or two rocket cultivars grown as sole crops in each block).

The characteristics of the carrot cultivars (cv.) are: 1) Brasília, vigorous dark green foliage, good resistance to burn–out leaves, low incidence of green or purple shoulder and roots with dark orange pigmentation, and it is recommended for sowing from October to February in the Center–West, North and Northeast of Brazil (Souza et al, 2002; Teófilo et al, 2009); 2) Esplanada, well adapted to Brazilian soil and climate, high resistance to burn–out leaves, low incidence of flowering in early summer, moderate resistance to gall nematodes, the roots are long, thin and uniform color, characteristics appropriate to the minimum processing (Vieira et al., 2005). The characteristics of the rocket cultivars are: 1) Cultivada, a traditional cultivar with good yield of packets, long and jagged sheets of light green color, height between 25 to 30 cm; 2) Folha Larga, high vigor of plants, early seedlings and production, with excellent market acceptance (Porto, 2008).

The intercropping system was established in growing alternate strips of vegetables (50 % of the area for carrot and 50 % for rocket) where each plot was composed of two strips of four rows of each vegetable, flanked by two rows (side border). In the intercropping system the total plots area was 2.88 m², the harvest area 1.60 m² containing 160 rocket plants in 0.20 m x 0.05 m spacing (two plants per hole) and 80 carrot plants in 0.20 m × 0.05 m spacing (one plant per hole). In sole crop the total plot area was 1.44 m², the harvest area 0.80 m² containing 80 rocket plants in the 0.20 m x 0.05 m spacing (one plant per hole) and 40 carrot plants in the 0.20 m x 0.10 m spacing (one plant per hole).

The population of plants recommended for sole crop in the region is approximately 500 000 plants ha^–1 for carrot (Barros Júnior et al, 1995) and 1 000 000 plants ha^–1 for rocket (Moura et al., 2008), not considering 30 % of traffic area (corridors and roads). However, for the variables in the crops, corrections were made to 70 % of cultivated area; these same population densities were also used in the intercropping systems.

Soil preparation consisted of harrowing followed by construction of beds. Before the installation of the field experiment, a solarization on the beds with transparent plastic Vulcabrilho Bril Fles (30 µ) was carried out for 56 d, in order to reduce soil phytopathogens which would undermine crops productivity.

In the plots with rocket and carrot in sole crop and intercropped, planting fertilizations were performed with 80 t ha^–1 cattle manure, 30 kg ha^–1 N (urea), 60 kg ha^–1 P₂O₅ (single superphosphate) and 30 kg ha^–1 K₂O (potassium chloride), according to soil analysis and recommendations (IPA, 1998). This high amount of manure was used as a source of N and P because these nutrients are low in soil and following recommendation by Alvares Venegas et al. (1999). Besides, this high amount of manure provides greater holding capacity of soil water, especially in this sandy soil.

The carrot and the rocket were direct and simultaneously sown on July 17, 2006. In the plots with rocket and carrot three to five seeds per hole were sown and 8 d after emergence the thinning of the rocket was performed; two seedlings per hole were left in the intercropping plots and one seedling in the sole crop plots. Thinning in carrot, the main crop, was carried out 25 d after sowing (das), leaving one plant per hole in the two cropping systems. The second sowing of the rocket was on September 27, that is, 73 d after the carrot sowing. This cultivation practice is common in the association of carrot and leafy vegetables in order to optimize space between strips of carrot rows, to increase the use efficiency of the area. In addition, the producer during the carrot cycle may dispose twice of rocket production and thus to increase income.

In the plots with rocket in sole crop fertilization with 40 kg ha^–1 N (urea) was carried out 15 das. Also, 25 and 30 d after rocket sowing, both cropping systems received foliar fertilization: 30 mL 20 L^–1 water, and 14 % N, 4 % P₂O₅, 6 % K₂O, 0.8 % S, 1.5 % Mg, 2 % Zn, 1.5 % Mn, 0.1 % B and 0.05 % Mo. Plots with carrot in sole crop and intercropped were fertilized with 40 kg ha^–1 N 25 and 45 das. Together with the first N fertilization, 30 kg ha^–1 K₂O was applied to the crops.

During the experiment, three hand weedings and two irrigations were applied daily by a micro–sprinkler system with a water sheet of about 8 mm h^–1. Two sprays were performed with Azadiracta indica A. Juss syrup, to combat aphids in the rocket (40 g dried neem leaves L^–1 water). The rocket was harvested on 20 August and 27 October 2006, about 30 das; carrot was harvested on 14 October 2006, at 89 das.

Variables evaluated in the carrot were: plant height, number of stems per plant, shoot and root dry matter mass, total and commercial productivity of roots (free of cracks, bifurcations, nematodes and mechanical damage). Productivity (%) of roots was classified according to its length and diameter as: long, lengths from 17 to 25 cm and diameter < 5 cm; medium, length from 12 to 17 cm and diameter > 2.5 cm; short, length 5 to 12 cm and diameter < 5 > 1 cm; scrap, roots not included int the previous interval (Vieira et al., 1997). The variables evaluated in the rocket were plant height, number of leaves per plant, yield of green mass and shoot dry matter mass.

Indexes for agronomic and economic efficiency of the intercropped systems between carrot and rocket cultivars were:

1) Land equivalent ratio (LER) to evaluate advantage in intercropping experiments (Willey and Osiru, 1972); it is the relative land area under sole crop conditions required to provide the yield reached in intercropping (Willey, 1979) and indicates the biological efficiency of intercropping for using the resources of the environment as compared to sole crop (Mead and Willey, 1980). It is calculated as follows: LER=LER_c+LER_r, where LER_c and LER_r represent LER of carrot and rocket in our study. If LER > 1 the intercropping favors growth and yield of component crops; if LER < 1 the intercropping negatively affects the growth and yield of crops grown in the association (Caballero et al., 1995).

2) Gross income (GI) is the value of combined yields in each intercrop system, irrespective of production costs (PC); GI = Y_cr P_c + Y_cr P_r, where Y_cr and Y_rc are the yields t ha^–1 of carrot and rocket as intercrops, and P_c and P_r are prices of 1 k of carrot and rocket (R$ 1.20 and R$ 4.90; 1 US$ = 1.77 R$) in December 2007, in Mossoró–RN, paid to farmers.

3) Net income (NI) was calculated as follows: NI = GI–PC, where PC is the summation of all expenses (inputs and labors) in each intercrop system.

A univariate variance analysis for a randomized complete block experiment with a 2×2+2 factorial arrangement of treatments was performed to evaluate the variables for carrot (Lentner and Bishop, 1986) (Table 1). A combined analysis of this same factorial in two crops (Table 2) was performed to evaluate the rocket variables. The treatment–factors means were compared using the Tukey test (p<0.05). All the analysis were performed using SAS (Cody and Smith, 2004).

 

RESULTS Y DISCUSSION

Carrot crop

A significant difference (p<0.05) was found between carrot cultivars for plant height, number of stems per plant, total and commercial productivity of roots and percentage of the carrot roots long and medium, short and scrap (Table 3). The average Brasília carrot was higher than that of the Esplanada in plant height, number of stems per plant, total and commercial productivity of roots and in the percentage of the short roots of carrot; while the average of the Esplanada surpassed that of the Brasília in the percentage of long, medium and scrap carrot roots (Table 4).

There was no significant difference (p>0.05) between Cultivada and Folha Larga rocket, which means that the pressures of competition exerted by these rocket cultivars were not strong enough to differentiate them, because the carrot and the rocket have distinct growth habits and development. This result differs from that obtained by Grangeiro et al. (2007), who indicate that crop cycle and the similarity of the plant appear to have been crucial to yielding lower beet (Beta vulgaris) productivity in the intercropping system. Although, the rocket had a short cycle with initial rapid growth, it mainly promoted greater interspecific competition for light when beet and rocket were sown simultaneously.

Significant interaction between carrot and rocket cultivars was not observed (p>0.05) for carrot variables. However, there was a significant difference (p<0.05) between the cultivars of carrots in single crop, total and commercial productivity and in the percentages of short and scrap roots of carrot. Brasília outperforming the Esplanada in the three first variables, and the Esplanada outperforming the Brasília in scrap roots (Table 4).

Significant differences (p<0.05) between the sole crop and intercropping system of carrot and rocket were found for dry matter mass of shoot and roots, total and commercial productivity and short roots (Table 3), with the sole cropping system outperformed the intercropping system 19.62 %, 20.98 %, 38.54 % and 37.03 %; in carrot short roots %, the intercropping system outperformed (40.38 %) sole crop (Table 4) . The reductions in carrot variables, in intercropping, were probably due to the higher density of plants within the line of planting.

The average of total carrot productivity was 22.00 and 35.80 t ha^–1, in both intercropping system and sole crop (Table 4), which are close to the average in the Northeast region (25 t ha^–1) according to Vilela et al. (1997). About 70 % of the carrot roots showed good quality and were within the commercial pattern, which agrees with Caetano et al. (1999), who report about 73 % commercial standard for intercropping systems of carrot and lettuce in alternate rows.

Rocket culture

No significant difference was observed between the carrot cv., rocket cv. and crops of rocket on plant height (Table 5), neither between sole crop and intercropping system and between rocket cv. in sole crop. These data agree with those obtained by Negreiros et al. (2002), who found a similar plant height of lettuce in both systems, when considering the intercropping of carrot with lettuce in alternate rows.

For the plant height there were no significant interactions (p>0.05) between cultivars of carrot and rocket. However, a significant interaction (p<0.05) was recorded between the rocket crops and carrot cv in the number of leaves per plant, yield of green matter mass and dry matter mass yield of the rocket shoot (Table 5). Partitioning the interaction of carrot cv. within rocket crops, higher average values were found in Esplanada in the second rocket crop (Table 6). Besides, there was a significant difference between the average values of the rocket crops within the Esplanada carrot cultivar with the highest value in the second crop; but no significant difference was found between rocket crops within the Brasília carrot (Table 6). The differences in performance of carrot cultivars might be explained by high temperature and ample light, and the differentiated adaptability of these genotypes to intercropping with the rocket. Between the rocket cultivars in intercropping and sole crop there was no significant difference in the number of leaves per plant, yield of green matter mass and dry matter mass of the rocket shoot. However, significant differences between sole crop and intercropping system were recorded in the number of leaves per plant and in the yield of green matter mass of the rocket, with the sole crop stand outperforming the intercropping system (Table 6). Management of production factors such as population arrangement, times of establishment of component crops in intercropping, among others, may minimize the competition and maximize the temporal or spatial complementarity of the crops. According to Trenbath (1976), the dry matter production of the plant depends on the efficiency of the interception of photosynthetic active radiation.

No significant interaction was found between carrot and rocket cultivars neither between these rocket cultivars, in sole crop and in intercropping system, for green and dry matter masses accumulated from two rocket crops (Table 7). However, there were significant differences between carrot cultivars and between sole versus intercropping, with the Esplanada cultivar outperforming the Brasília cultivar in dry matter mass of the rocket shoot. A similar response between these cultivars was observed in the yield of rocket green mass.

The intercropping system outperformed the sole crop on the yield of rocket green mass, while the sole crop outperformed the intercropping in the rocket shoot dry matter mass (Table 8). This result was due to the higher moisture content in the rocket as a result from a micro climate formed by the intercropping system between the rocket and carrot. Furthermore, the lowest value for the rocket dry matter mass came from water withdrawal during the drying process.

The indexes of agronomic and economic efficiency of the intercropping systems of carrot and rocket cultivars (Table 9) showed an gain of the intercropped systems (LER values >1). The highest agronomic and economic indexes were observed in the intercropped systems containing carrot cultivar Brasília plus the rocket cultivars Cultivada or Folha Larga. The analysis of these results shows the monetary advantage of LER, indicating that the agronomic superiority in the studied systems resulted in economic advantages.

 

CONCLUSIONS

There was a significant interaction between rocket crops and carrot cultivars on the productive performance of the rocket. This variable was largest in the second crop and in the Esplanada carrot cultivar. Regardless of the rocket crops, the Cultivada and Folha Larga cv. showed similar productive performances in sole crop and intercropping system. The best performance of the rocket was observed in the second crop. The highest yield of rocket green mass was recorded in the intercropping system and the rocket dry matter mass in sole crop. The Brasília carrot showed the best productive performance in sole crop and intercropping system. Carrot commercial roots were similar in the both systems. The intercropped systems of carrot Brasília + rocket Cultivada and carrot Brasília + rocket Folha Larga showed the best association, based on agronomic and economic efficiency.

 

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