Effects of boron on lettuce

One of the ways to make lettuce planting viable lies in increasing productivity. The use of boron, in soil and foliar application, is seen as an alternative to assist in this process

15.01.2018 | 21:59 (UTC -3)

The lettuce (lactuca sativa L.) belongs to the Asteraceae family, the group of vegetables most consumed in salads in Brazil (Filgueira, 2003), with a production of 525.603 tons in 2006, where the Southeast region contributed with 66,7% of this production (IBGE, 2012 ). The state of Amazonas is not self-sufficient in primary sector production, especially horticultural production, producing the equivalent of 0,14% of national production and Manaus, with a population of over 1,8 million inhabitants (IBGE, 2012), if Today, it is characterized as a large urban consumer center, and to meet this demand, the majority of vegetables come from other regions of the country.

In retail markets, we can see the predominance of hydroponic lettuce, which is the main production system in the region. The production of lettuce in a hydroponic system, in a study carried out in Lavras, Minas Gerais, demonstrated that the activity under the conditions presented does not have the capacity to cover the total costs and the producer is in a process of decapitalization, which, in the medium and long term deadline, will make him leave the activity. To equalize total revenue with total cost, either productivity increases by 2% or sales price increases by 3% (Geisenhoff et al.

Protected cultivation in the Amazon focuses on two products: peppers and coriander. Lettuce is a possible cultivation alternative to use, with a short cycle, the area from other crops. Manaus is a large consumer center and the regional production of curly and American lettuce is sold in the market. However, iceberg lettuce, due to the edaphoclimatic conditions of the Amazon region, does not have its characteristic head shape, which, according to Filgueira (2003), has consistent leaves, with the veins highlighted, forming a more compact head. There are reports of positive effects of applying boron to lettuce, with increased production, plant and head circumference (Yuri et al, 2004; Chutichudet & Chutichudet, 2009). Therefore, with the aim of promoting gains in production and head size and weight, an experiment was carried out to evaluate the effect of boron on iceberg lettuce in the edaphoclimatic conditions of Amazonas. 

 The experiment

The experiment was conducted between April and June 2011, in the municipality of Iranduba, Amazonas, in a producer area, located at coordinates 3º13'3,74”S and 60º13'24,08”W, under a chapel-type greenhouse, with wooden structure and the following dimensions: seven meters wide by 45 meters long and a ceiling height of three meters. The cover was made with transparent low-density polyethylene plastic (LDPE) and was 100μm thick.

The experimental design used was in randomized blocks with eight replications, in plots of four rows with 24 plants, with a spacing of 0,3m x 0,3m. The cultivar Lucy Brown was used in the test. 13 treatments were applied, with T0 = control (absence of boron); T1 = 0,5; T2 = 2,0; T3 = 3,5 and T4 = 5,0kg/ha of decahydrated sodium borate applied to the soil, 15 days before transplanting (DAT); T5 = 0,5kg/ha; T6 = 2,0kg/ha; T7 = 3,5kg/ha and T8 = 5,0kg/ha of sodium borate decahydrate via foliar, divided into three applications (at 7, 14 and 21 days after transplanting, with 30%, 30% and 40% of the dose , respectively); T9 = 0,5; T10 = 2,0; T11 = 3,5 and T12 = 5,0kg/ha of sodium borate decahydrate via foliar, in a single dose at 14 DAT.

The seedlings were produced in Styrofoam trays with 200 cells, using one seed/cell, in commercial substrate and in a protected environment. In the production of seedlings, commercial foliar fertilizer was applied, consisting of N, Ca and Mg, with 132g/L, 106g/L and 45g/L, respectively, at a concentration of 1ml/L.

In the base fertilizer, the equivalent of 40kg of chicken manure/60m field was applied to prepare the area.2, 150kg N/ha, 50kg K2O/ha and 25kg of P2O5/ha and, 25 days after transplanting, through fertigation, 1kg of urea was applied/720 meters of planting line.

The seedlings were transplanted 30 days after sowing, when the plants had four definitive leaves. Cultivation coincided with the period called “summer”, that is, a time with lower rainfall in the northern region and in which, under protected cultivation, the temperature tends to increase.

The harvest took place 35 days after transplanting the seedlings, where the following parameters were evaluated: total fresh biomass (with the removal of damaged leaves), fresh head biomass, head diameter, fresh stem mass. Data analyzes were carried out using statistical software (Irristat, v.5.0) developed by International Rice Research Institute (Irri)

 Preliminary results

Under the conditions of this work, the results found (Table 1) demonstrated that the treatments did not cause significant effects on the diameter of the head and on the fresh biomass of the head, despite resulting in an increase of 13% and 38%, respectively, when compared to the witness. However, the use of 5 kg of decahydrated sodium borate per hectare via foliar and split (T8) promoted greater accumulation of fresh biomass than the use of 3,5 kg of decahydrate sodium borate per hectare via foliar and split ( T7). This dose was more than twice the dose of 1,71kg/ha applied via foliar 21 days after transplanting, which provided better yield and commercial quality of iceberg lettuce in a trial conducted in winter in Minas Gerais (Yuri et al, 2004). The edaphoclimatic conditions of Amazonas encourage the precocity of plants, as temperatures and length of days exceed the optimal conditions for maintaining a longer vegetative phase (Filgueira, 2003; Resende et al, 2007). Thus, while in trials under climatic conditions with milder temperatures, with harvests with longer cycles, the fresh biomass of plants reaches weights greater than 600g (Resende et al, 2005; Yuri et al, 2004), under Amazonian conditions and in the summer period, the average total fresh biomass of the aerial part in this trial was around 122g. The number of leaves on the head, obtained with T11 (3,5kg/ha of decahydrated sodium borate, applied foliarly at 21 DAT), was higher than the T7 and T8 treatments, a characteristic that is important for yield when used in salads.

In a contrast study (Table 2), it was possible to observe that the use of boron doses did not promote gains in any of the evaluated parameters when compared with the control, despite the positive effects of the use of boron in other lettuce trials (Yuri et al, 2004; Chutichudet & Chutichudet, 2009). In contrast between the use of boron via foliar or soil, foliar use allowed a significant gain in total fresh biomass and head diameter. The use of foliar boron in a single dose surpassed, in terms of number of leaves on the head, the use of foliar boron in installments. Although the use of boron did not significantly surpass the behavior of the control treatment, the contrasts offer the prospect of maintaining an investigative path for the use of boron via leaves, in iceberg lettuce, in Amazonian conditions.

Tabela 1 - Effects of applying doses of boron via soil and foliar on iceberg lettuce, cultivar Lucy Brown, in protected cultivation, under the conditions of Amazonas Iranduba/AM, Embrapa Amazônia Oeste, 2011

Treatments1

Total fresh biomass

(g.plant-1)

Head diameter

(Mm)

Fresh head biomass (g.plant-1)

Number of leaves on the head (un.plant-1)

 T02

128,88 ab1

94,45 to

68,76 to

12,25 ABC

T1

131,00 ab

96,13 to

73,16 to

12,50 ABC

T2

96,13 ab

72,97 to

56,10 to

12,37 ABC

T3

104,13 ab

92,98 to

54,12 to

11,13 ABC

T4

106,50 ab

75,58 to

56,39 to

11,50 ABC

T5

134,38 ab

84,63 to

70,09 to

12,00 ABC

T6

92,50 ab

72,72 to

69,69 to

9,87 c

T7

90,63 b

98,20 to

44,69 to

10,25 bc

T8

162,75 to

99,66 to

87,50 to

13,63 ABC

T9

97,50 ab

74,34 to

54,02 to

11,38 ABC

T10

158,25 ab

105,70 to

95,46 to

15,00 ab

T11

144,25 ab

106,50 to

90,49 to

15,25 to

T12

135,63 ab

87,50 to

68,20 to

13,38 ABC

Treatments1

Total fresh biomass

(g.plant-1)

Head diameter

(Mm)

Fresh head biomass (g.plant-1)

Number of leaves on the head (un.plant-1)

 T02

128,88 ab1

94,45 to

68,76 to

12,25 ABC

T1

131,00 ab

96,13 to

73,16 to

12,50 ABC

T2

96,13 ab

72,97 to

56,10 to

12,37 ABC

T3

104,13 ab

92,98 to

54,12 to

11,13 ABC

T4

106,50 ab

75,58 to

56,39 to

11,50 ABC

T5

134,38 ab

84,63 to

70,09 to

12,00 ABC

T6

92,50 ab

72,72 to

69,69 to

9,87 c

T7

90,63 b

98,20 to

44,69 to

10,25 bc

T8

162,75 to

99,66 to

87,50 to

13,63 ABC

T9

97,50 ab

74,34 to

54,02 to

11,38 ABC

T10

158,25 ab

105,70 to

95,46 to

15,00 ab

T11

144,25 ab

106,50 to

90,49 to

15,25 to

T12

135,63 ab

87,50 to

68,20 to

13,38 ABC

1Means with the same letters and in the same column do not differ statistically from each other using the Tukey test (5%).

2T0 = ​​control (absence of boron), treatments with application of decahydrated sodium borate (borax) to the soil 15 days before transplanting:  T1 = 0,5; T2 = 2,0; T3 = 3,5 and T4 = 5,0kg/ha-1, treatments with borax application via foliar, divided into three applications (at 7, 14 and 21 days after transplanting): T5 = 0,5; T6 = 2,0; T7 = 3,5 and T8 = 5,0kg/ha-1 and treatments with application of borax via foliar, in a single dose at 14 days after transplanting): T9 = 0,5; T10 = 2,0; T11 = 3,5 and T12 = 5,0kg/ha-1.

 

Tabela 2 - Means of treatments and absolute difference between means of contrasts (׀ŷ׀) of treatments for lettuce production characteristics. Iranduba/AM, Embrapa Western Amazon, 2011

Details of the product

Media

 

׀ŷ׀

TS1

TA

TB

TC

TD

TE

 

TA

x

TS

TC

x

TB

TE

x

TD

Total fresh biomass

(g.plant-1)

128,9

121,1

109,4

127,0

120,1

133,9

 

7,74ns

17,55*

13,84 ns

Head diameter (cm)

94,5

88,9

84,4

91,2

88,8

93,5

 

5,54ns

6,74*

4,71 ns

Fresh head biomass (g.plant-1)

68,8

68,3

59,9

72,5

68,0

77,0

 

0,43ns

12,58 ns

9,05 ns

Number of leaves on the head (un.plant-1)

12.3

12.4

11.9

12.6

11.4

13.8

 

0.10ns

0.72 ns

2.32**

Details of the product

Media

 

׀ŷ׀

TS1

TA

TB

TC

TD

TE

 

TA

x

TS

TC

x

TB

TE

x

TD

Total fresh biomass

(g.plant-1)

128,9

121,1

109,4

127,0

120,1

133,9

 

7,74ns

17,55*

13,84 ns

Head diameter (cm)

94,5

88,9

84,4

91,2

88,8

93,5

 

5,54ns

6,74*

4,71 ns

Fresh head biomass (g.plant-1)

68,8

68,3

59,9

72,5

68,0

77,0

 

0,43ns

12,58 ns

9,05 ns

Number of leaves on the head (un.plant-1)

12.3

12.4

11.9

12.6

11.4

13.8

 

0.10ns

0.72 ns

2.32**

*, **Significant at 5% and 1% probability by the F test and  nsNot significant

1TS = Absence of boron; TA = Boron use; TB = Application of boron via soil, 15 days before transplanting; TC = Boron application via foliar; TD = Boron application via foliar splits (7, 14 and 21 days after transplanting, with 30, 30 and 40% of the dose, respectively); TE =  Boron application via foliar in a single dose.

 

Click here to read the full article in issue 78 of Cultivar Hortaliças e Frutas.


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