ABSTRACT

Plant densities that decrease interplant competition can improve Moringa oleifera growth and yield by better use of resources and information about its cultivation in the autumn/winter season is necessary. An experiment was conducted to investigate the viability for the cultivation under the edafoclimatic conditions of the southern Brazil, region of subtropical climate. In addition, it was determined effect of planting densities on the initial growth of moringa (M. oleifera Lam.) plants. The experiment was carried out from April to July 2012, autumn/winter season, on a clayey Rhodic Hapludox in Marechal Cândido Rondon, Paraná State, Brazil. Treatments were arranged in a randomized block design in a 2 × 3 factorial: two evaluation periods (30 and 60 days after plant emergence) and three plant densities (14,815; 22,222 and 44,444 plant ha^–1), with four replications. When grown at lower population densities, the initial growth of moringa plants is not affected. The initial growth of moringa plants in the southern region of Brazil, on autumn/winter season was unsatisfactory due the occurrence of low temperatures. The moringa showed a high mortality rate under low temperature and does not seem to be recommended, in principle, to compose an agroforest system with edafoclimatic conditions similar to those of the studied region.

Key words: Plant population, vegetative growth, adaptation.

Study site description

 

The experiment  was  carried  out  at  the  Agronomic  Experimental Station, Universidade Estadual do Oeste do Paraná (State University of West Paraná), in Marechal Cândido Rondon Municipality, Paraná State, Brazil (24°31' S, 54°01' W and 390 m asl), during the months of April and July of 2012. The soil was a clayey Rhodic Hapludox (Eutroferric Red Latosol in the Brazilian classification) with 620, 270 and 110 g kg^–1 of clay, silt and sand, respectively. Before starting the experiment, soil samples were collected at depths of 0.0–0.10; 0.10–0.20 and 0.20–0.40 m. The results of chemical analysis are shown in Table 1.

 

 

The southern region of Brazil is characterized by a humid subtropical climate. The average annual temperature is 20.9°C. The month of January is the hottest of the year (average 23.8°C) and the coldest month is June (average 16.6°C). The average annual rainfall is about 1600 mm, with rainfall during the summer (December = 230 mm) is about two times higher than in winter (August = 51 mm), featuring two stations well defined (Bianchini et al., 2001). The State of Paraná is located in a climatic transition zone, from the subtropical to temperate conditions prevail in which, in general, three types of climate. These are defined by the location, temperature and rainfall cycles. In western Paraná, predominates mesothermal humid subtropical climate with hot summers, no dry season with occasional periods of frost (Carvalho and Queiroz, 2002). In the state, there are few locations without risk of severe frost or under frost every 10 years (Wrege et al., 2004). The regional climate is relatively warm and wet with low temperatures in the winter. Rainfall and temperature data gathered during the experiment are shown in Figure 1.

 

 

Experimental design and treatments

 

The experimental design was a 2 × 3 factorial in randomized complete blocks with four replications. Treatments consisted of two evaluation periods (30 and 60 days after plant emergence) and three plant densities (14,815; 22,222 and 44,444 plants ha^–1). Uniform spacing between rows (0.90 m) was used in all plots. With the aim of obtaining three different planting densities (14,815; 22,222 and 44,444 plants ha^–1), 0.75; 0.50 and 0.25 m spacing’s between plants were used within rows. The individual plot size was 18 m² (3.6 m wide × 5.0 m long) and the net area used for harvest was 7.2 m² to eliminate edge effects.

 

Field management and measurements

 

Moringa (M. oleifera Lam., Syn. Moringa pterygosperma Gaertner) seeds were sown on 03 April 2012, in 0.90 m spaced rows at densities studied. Untreated seeds of moringa were used for propagation. Seeds were sown in 2.0 cm deep holes at the study site (two seeds per hole). After two weeks of growth, the stand was thinned and only one healthy plant was kept. Mineral fertilization was carried out by applying 200 kg ha^–1 of a commercial formulated 08-20-20 (N, P₂O₅ e K₂O, respectively), at sowing, and 90 kg ha^–1 N top dressing in the form of urea at the beginning of plant’s tillering. Irrigation was not applied. Weeds were controlled manually three weeks after germination and  every  second  month  throughout  the experiment. The following parameters were used for data collection: plant height measurements and stem diameter at 15 cm base height were taken at 30 and 60 days after plant emergence (DAPE).

 

Statistical analysis

 

Original data were analyzed by ANOVA, and means of plant density were compared by the Tukey test at the 0.05 level of confidence. All analysis was performed using Sisvar 5.1 software for Windows (Statistical Analysis Software, UFLA, Lavras, MG, BRA).

 

A summary of the analysis of variance for plant height and stem diameter is shown in Table 2. Period effect on plant height and stem diameter of moringa was significant (P < 0.05). Planting density had no significant effect on plant height and stem diameter of moringa plants. There was no significant interaction between the effects of evaluation periods and planting density on the plant height and stem diameter (Table 2).

 

 

The effect of evaluation periods on plant height and stem diameter of moringa is shown in Table 3. The plants evaluated at 60 days showed greater plant height and stem diameter compared plants evaluated at 30 days (Table 3). Indicating that there was plant growth although there has been only a small growth rate (1.4 cm in height and 0.3 mm in diameter). The small plant growth occurred in the second evaluation (60 days after emergence) compared to the first evaluation (30 days after emergence) was due to the low temperatures recorded in the period of plant development (Figure 1). There were no reports of moringa cultivation under low temperature conditions. The younger the plant, the greater the damage to the leaves, stems and branches by frosts, due to the higher sensitivity of the vegetative material due to the proximity to the ground, where the temperature inversion is more pronounced (Caramori et al., 2000).

 

 

The effect of the three planting densities on plant height and stem diameter of moringa is shown in Table 4. The plant height and stem diameter of moringa were not significantly different between plant densities (Table 4). Similar finding was reported by Reyes-Sánchez et al. (2006b) when they evaluated the planting densities of 250,000; 500,000; and 750,000 plants ha^–1 and the DM yield of moringa was not affected. Manh et al. (2005) also reported no effect of density on DM yield when densities of 125,000 plants ha^–1 or lower were used. Goss (2012) found that population density reduced the stem diameter of moringa plants at high populations while increasing them at low densities. Studies done on other multipurpose trees indicate that increases in plant population density results in an increase in the plant growth with resources being utilized when roots and stems entangle and when each plant competes with its neighbor (Squire, 1990). In production systems suitable plant densities are used, the plants efficiently utilize soil and environmental conditions, and the inter-or-intra-specific competition is reduced (Sadeghi et al., 2009). A positive relationship between planting density and DM yield  in  tropical  tree  legumes  such  as  M. oleifera  has been reported (Mendieta-Araica et al., 2013; Sadeghi et al., 2009; Foidl et al., 2001).

 

 

Foidl et al. (2001) reported increasing DM production from 3.3 to 44 Mg ha^–1 at 95,000 and 16,000,000 plants ha^–1, respectively. However, due to the high mortality at very high planting densities, those authors recommended 0.10 × 0.10 m or 1,000,000 plants ha^–1 as the optimum. In another study, Mendieta-Araica et al. (2013) found that the planting densities of 167,000 plants ha^–1 was best compared to density 100,000 plants ha^–1, due to the possibility of achieving very high dry matter yield (19 Mg ha^–1) with a high proportion of ?ne fraction yield. Although, high densities are positively correlated with high DM yields, the spatial arrangement in the ?eld, the high amount of labour needed and dif?culties during harvesting make high densities impractical for small and medium-scale farmers (Mendieta-Araica et al., 2013).

 

The initial growth of moringa plants was impaired by the occurrence of low temperatures, which triggered an increase plant mortality rate. The average mortality rate of moringa plants was 60% (data not shown). At occurrence of low temperatures around 1.5°C (Figure 1) in the period in which the plants found 45 days affected the survival of moringa plants, compromising the crop development. Based on results presented here, we infer that the moringa genotype used in this study is sensitive to low temperature conditions. Therefore, the moringa cultivation in the Paraná State, Brazil, on autumn/winter season, should not be recommended because at low temperatures negatively affects the crop establishment.

 

The susceptibility of the crop to low temperatures varies greatly according to the species and phenological stage of the plants (Camargo et al., 1993). With the aim of verify, the adaptability of native tree species submitted to extreme frost stress under an agroforestry system in southern Brazil, Vieira et al. (2003) found that species such as Brazilian coral tree (Erythrina falcata Benth), guanandi (Calophyllum brasiliense Cambess.) and licurana (Hieronyma alchorneoides Allemão) showed a high mortality rate under frost, and did not show a good potential to compose an agroforest system in a region of low temperatures like in southern Brazil.

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