New tools for understanding crops: Measuring Soil Electrical Conductivity
By Marcio Albuquerque, engineer, member of the Precision Agriculture Sector Chamber, director of Falker Automação Agrícola
17.08.2016 | 20:59 (UTC -3)
Silicon (Si) is one of the most abundant chemical elements in the Earth's crust, and some plants, such as corn and other grasses, mainly, accumulate this element. The use of silicon sources in agriculture meets the need for alternatives for efficient phytosanitary control, in addition to the search for strategies that offer reduced risk to the environment.
When silicon is absorbed by the plant and deposited in the wall of the plant cell, it no longer moves, it subsequently polymerizes and causes the formation of a double layer of cuticular silicon, causing the wall to stiffen, which brings several already proven benefits, whether in abiotic and/or biotic factors.
In abiotic factors, the regulation of evapotranspiration is among the main aspects, in addition to the reduction of toxicity caused by aluminum and iron in plants. Regarding biotic factors, insect control stands out, including Spodoptera frugiperda in corn, the main pest of the crop. Effective disease control is also observed, which can be attributed to the increased difficulty in penetration and colonization of fungi. Silicon has already proven its beneficial effect on these two factors in several crops, such as rice, cotton, coffee, sugar cane, corn, soybeans and wheat. Currently, silicon can be obtained in different ways, its application can also be varied, such as soil applications followed by incorporation and foliar applications.
In work conducted in the municipality of Campo Verde, Mato Grosso, using a randomized block design, eight treatments were tested (Table 1), repeated in four blocks, with the aim of evaluating the reduction in the incidence of helminthosporiosis, a disease that has as a causal agent the fungus Exserohilum turcicum. It is an aggressive disease, which can lead to losses of up to 50% in attacks before the flowering period. The treatments consisted of two sources of silicon: calcium and magnesium silicate, used in four doses applied as top dressing and incorporated into the soil before planting, and also potassium silicate (foliar application at the stage of six expanded true leaves) in a single dose. . Furthermore, a treatment was adopted in which an interaction between these sources was used. Two controls were also used, one from conventional corn and the other from transgenic corn, with Yieldgard technology.
TABLE 1 - Different doses and forms of application of silicon to control helminthosporiosis in corn. Campo Verde – MT, 2012
| Treatment | Hybrids | Dose (Kg.Ha-1) |
| 1 | Control - Conventional Corn – With Insecticides | - |
| 2 | Witness - Corn Bt (Yieldgard) | - |
| 3 | Conventional Corn - Ca and Mg Silicate1 | 400 (Kg.Ha-1) |
| 4 | Conventional Corn - Ca and Mg Silicate1 | 600 (Kg.Ha-1) |
| 5 | Conventional Corn - Ca and Mg Silicate1 | 800 (Kg.Ha-1) |
| 6 | Conventional Corn - Ca and Mg Silicate1 | 1000 (Kg.Ha-1) |
| 7 | Conventional Corn - Potassium Silicate2 | 1 (Lt.Ha-1) |
| 8 | Conventional Corn – Ca and Mg Silicate1and Potassium Silicate2 | 400 (Kg.Ha-1) + 1 (Lt.Ha-1) |
Treatment
Hybrids
Dose (Kg.Ha-1)
1
Control - Conventional Corn – With Insecticides
-
2
Witness - Corn Bt (Yieldgard)
-
3
Conventional Corn - Ca and Mg Silicate1
400 (Kg.Ha-1)
4
Conventional Corn - Ca and Mg Silicate1
600 (Kg.Ha-1)
5
Conventional Corn - Ca and Mg Silicate1
800 (Kg.Ha-1)
6
Conventional Corn - Ca and Mg Silicate1
1000 (Kg.Ha-1)
7
Conventional Corn - Potassium Silicate2
1 (Lt.Ha-1)
8
Conventional Corn – Ca and Mg Silicate1and Potassium Silicate2
400 (Kg.Ha-1) + 1 (Lt.Ha-1)
1Application on the ground and incorporated
2Application via foliar spray at the six expanded leaf stage (V6)
The assessment of the incidence of helminthosporiosis was carried out in R5 (teeth formation), in three specific leaves: the leaf below the upper ear, the leaf on the upper ear and the leaf above the upper ear. As shown in Table 2, it was possible to observe a significant reduction in the incidence of the disease on the leaves and below the cob when using any of the two silicon sources used, regardless of the dose. As for the leaf above the ear, there was no statistical difference due to the low incidence in the upper part of the plant, as this disease occurs progressively from the base to the apex of the plant. The number of plants with incidence of the disease was also reduced, showing an increase in resistance to infection by this pathogen. Although there was no statistical difference, the production data showed higher values for the treatments where silicon was used (Table 3).
TABLE 2 - Incidence of helminthosporiosis (%) in leaves below the cob (Below), leaves on the cob (Ear), leaves above the cob (Above) and percentage of plants showing disease (Plants). Campo Verde – MT, 2012
| Treatment | Bellow1 | Spike | Above | Plants | |||||
| 1 | 7,45 | B | 6,75 | B | 4,05 | A | 8,61 | B | |
| 2 | 8,70 | B | 7,66 | B | 5,84 | A | 9,52 | B | |
| 3 | 3,68 | A | 2,79 | A | 1,89 | A | 4,59 | A | |
| 4 | 4,49 | A | 1,00 | A | 1,89 | A | 5,38 | A | |
| 5 | 3,24 | A | 4,59 | A | 2,79 | A | 6,75 | A | |
| 6 | 4,71 | A | 4,58 | A | 1,89 | A | 6,59 | A | |
| 7 | 1,89 | A | 3,24 | A | 4,14 | A | 5,84 | A | |
| 8 | 4,59 | A | 3,68 | A | 3,68 | A | 6,29 | A | |
| CV%2 | 45,73 | 40,96 | 66,05 | 23,52 | |||||
| Overall Average2 | 4,89 | 4,29 | 3,27 | 6,70 | |||||
Treatment
Bellow1
Spike
Above
Plants
1
7,45
B
6,75
B
4,05
A
8,61
B
2
8,70
B
7,66
B
5,84
A
9,52
B
3
3,68
A
2,79
A
1,89
A
4,59
A
4
4,49
A
1,00
A
1,89
A
5,38
A
5
3,24
A
4,59
A
2,79
A
6,75
A
6
4,71
A
4,58
A
1,89
A
6,59
A
7
1,89
A
3,24
A
4,14
A
5,84
A
8
4,59
A
3,68
A
3,68
A
6,29
A
CV%2
45,73
40,96
66,05
23,52
Overall Average2
4,89
4,29
3,27
6,70
1Means followed by the same letter do not differ significantly from each other using the Scott-Knott test, at a 5% significance level.
2Data transformed by the equation: (X+1)^0,5
TABLE 3 - Corn production (weight of 100 grains and bags/ha) after application of different forms and doses of silicon. Campo Verde – MT, 2012
| Treatment | Weight of 100 Grains | grain production | |||||
| Bags.hectare-1 | Group | ||||||
| 1 | 31,80 | A | 115,59 | A | |||
| 2 | 31,35 | A | 116,65 | A | |||
| 3 | 30,98 | A | 117,14 | A | |||
| 4 | 32,32 | A | 117,58 | A | |||
| 5 | 32,23 | A | 119,2 | A | |||
| 6 | 32,04 | A | 119,27 | A | |||
| 7 | 31,65 | A | 119,48 | A | |||
| 8 | 32,44 | A | 119,98 | A | |||
| CV%2 | 6,05 | 5,45 | |||||
| Overall Average2 | 31,85 | 118,11 | |||||
Treatment
Weight of 100 Grains
grain production
Bags.hectare-1
Group
1
31,80
A
115,59
A
2
31,35
A
116,65
A
3
30,98
A
117,14
A
4
32,32
A
117,58
A
5
32,23
A
119,2
A
6
32,04
A
119,27
A
7
31,65
A
119,48
A
8
32,44
A
119,98
A
CV%2
6,05
5,45
Overall Average2
31,85
118,11
1Means followed by the same letter do not differ significantly from each other using the Scott-Knott test, at a 5% significance level.
2Data transformed by the equation: (X+1)^0,5
Based on the precepts of Integrated Pest and Disease Management, the use of silicon from sources that can be found on the market is beneficial. This element constitutes an important tool in the fight against pests and diseases, mainly due to the growing selection of individuals resistant to agrochemicals, whether due to lack of technical knowledge or population variability. Silicon may come to collaborate as a alternative control for those that persisted after the application of pesticides, making survival and subsequent multiplication difficult.
Click here to read the article in issue 178 of Cultivar Grandes Culturas.
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