Cowpea, string Bean, or Macassar bean [ Vigna unguiculata (L.) Walp] presents a short life cycle, low water requirement, develops in soils of low fertility, and has the ability to fix nitrogen from the air. In the Cerrado, the oxisols occupy practically all the flat to soft-wavy areas with little reserve of nutrients for the plants, in general, they are soils with great limitations of fertility. A source of alternative phosphate fertilization is the use of reactive natural phosphates. The reactive natural phosphate of Bayóvar presents intermediate solubility between the sources of soluble phosphates and the natural phosphates. In this context, the objective was to evaluate the initial development of Cowpea beans fertilized with the natural Bayóvar phosphate used for cultivation of the Brazilian Cerrado Oxisol. The experimental design was completely randomized, with six doses of phosphorus (0, 100, 200, 300, 400, 500 mg · dm - 3 ) using natural Bayovar phosphate as a source in four replications. The species used in this study was the legume cowpea bean [ Vigna unguiculata (L.) Walp] cultivar Tumucumaque. The treatments were applied using the natural phosphate Bayóvar as a source of phosphorus (29% of P2O5). At 33 DAS (days after sowing), the variable number of leaves of the Cowpea bean was analyzed and at 40 DAS, the variables plant height, SPAD chlorophyll index (Soil Plant Analysis Development) and stem diameter were analyzed. For all variables analyzed there was a significant effect. The initial development of the cowpea bean cultivated in the Brazilian Cerrado Oxisol was significantly influenced by the Bayóvar natural phosphate fertilization with the best phosphorus (P2O5) doses in the range of 200 to 350 mg ·
Cowpea, string Bean, or Macassar bean [Vigna unguiculata (L.) Walp] is an excellent source of protein (23% to 25% on average) and contains all essential amino acids, carbohydrates (62% on average), vitamins and minerals, as well as a large amount of dietary fiber and low amount of fat (oil content of 2% on average). It serves as basic food for the low-income populations of the Brazilian Northeast. It presents a short life cycle, low water requirement, develops in soils of low fertility, and has the ability to fix nitrogen from the air, through symbiosis with bacteria of the genus Rhizobium [
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Cowpea beans are grown mainly in the semi-arid interior of the Northeast and in small areas in the Amazon. In these regions, traditional practices of cultivation still predominate, with low use of technologies and low grain yields. However, with the advent of technologies that allow its fully mechanized cultivation, there has been an increase in the area of cultivation, production and productivity in the Midwest region, notably in the State of Mato Grosso. In this state, the reality is different, cowpea is cultivated on a large scale, with the participation of medium and large producers, presenting the highest yields of grains [
In the Cerrado, the oxisols occupy practically all the flat to soft-wavy areas with little reserve of nutrients for the plants, usually represented by their low to average cation exchange capacity. More than 95% of the dystrophic and acidic Oxisol, have pH between 4.0 and 5.5 and extremely low available phosphorus levels, almost always inferior to 1 mg・dm−3. In general, they are soils with great limitations of fertility [
As a result of its participation in the so-called energy-rich compounds, such as adenosine triphosphate (ATP), phosphorus plays a fundamental role in plant life, being essential in cell division, reproduction and plant metabolism such as photosynthesis, respiration and the synthesis of organic substances [
In order to guarantee a good agricultural production in the Cerrado, due to the low availability of phosphorus and its dynamics in the soil, fertilization with high doses of phosphorus is required, and this results to a great increase in production costs [
A source of alternative phosphate fertilization is the use of reactive natural phosphates, which, although undergo solubilization more slowly in the soil compared to industrial fertilizers, are a lower cost alternative for phosphorus fertilization because they are ores with less industrial processes [
The reactive natural phosphate of Bayóvar presents intermediate solubility between the sources of soluble phosphates and the natural phosphates. It is a phosphate of sedimentary origin and is characterized to present a high degree of isomorphic substitution of the phosphate ion by carbonate, which gives it a higher rate of reaction in the soil when compared to other natural phosphates [
In this context, the objective was to evaluate the initial development of Cowpea beans fertilized with the natural Bayóvar phosphate used for cultivation of the Brazilian Cerrado Oxisol.
The experiment was conducted in a greenhouse at the Federal University of Mato Grosso (16˚27' South latitude, 54˚34' West longitude and 284 meters altitude), Campus Universitário de Rondonópolis. The climate of the region is Aw, according to the classification of Köppen, with rainy summer and long periods of drought during the year. The average annual temperature was 24.8˚C. The soil used was the Red Oxisol [
The experimental design was completely randomized, with six doses of phosphorus (0, 100, 200, 300, 400, 500 mg・dm−3) using natural Bayovar phosphate as a source in four replications.
The species used in this study was the legume cowpea bean [Vigna unguiculata (L.) Walp] cultivar Tumucumaque. The soil was corrected by increasing the base saturation to 60% using calcareous dolomite (28% CaO and 20% MgO) and Total Neutralizing Power of 80.3%. After the incorporation of limestone, the soil was incubated for 20 days with the humidity maintained at 60% of its maximum soil retention capacity, using the gravimetric method [
After the incubation period of the calcareous soil, the treatments were applied
pH | P | K | Ca | Mg | H | Al | SB | CEC | V | O.M. | Sand | Silt | Clay |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
CaCl2 | mg・dm−3 | -------------------cmolc・dm−3--------------- | % | gd・m−3 | --------g・kg−1-------- | ||||||||
4.0 | 1.4 | 23 | 0.4 | 0.2 | 5.4 | 0.8 | 0.7 | 6.8 | 9.7 | 27.1 | 423 | 133 | 444 |
using the natural phosphate Bayóvar as a source of phosphorus (29% of P2O5). Potassium fertilization (K2O) of 80 mg・dm−3 was used as the source of potassium chloride and micronutrients with 15 mg・dm−3 of FTE (Fritted Trace Elements), in all treatments. Thereafter, sowing was done, and 5 seeds were arranged per pot, and after seven days thinning was done, leaving only two plants per pot.
At 33 DAS (days after sowing), the variable number of leaves of the Cowpea bean was analyzed and at 40 DAS, the variables plant height, SPAD chlorophyll index (Soil Plant Analysis Development) and stem diameter were analyzed.
The number of leaves was obtained by counting in each vase. The height of plants was measured with a graduated ruler, from the soil to the apex of each plant present in the vase, with an average to compose the height of the plot. The chlorophyll index was determined using the Minolta SPAD-502 chlorophyll meter. For the determination of the diameter of the stem an analog pachymeter was used at a height 2 cm from the soil surface.
The results were submitted to regression analysis and significance was determined at 5% error of probability, using the statistical program Sisvar [
For the variable plant height in the Cowpea beans, there was a significant effect as a function of the phosphorus doses, adjusting to the quadratic regression model. The dose of phosphorus (P2O5) that provided higher plant height (42.62 cm) was 276.7 mg・dm−3, with an increase of 22.95% when compared to the absence of phosphate fertilization (
Based on the results, it is possible to observe the importance of phosphorus to the crop, which has limited growth due to the low amount of phosphorus available
in the soil. The plants present several ways of alleviating the problems caused by phosphorus deficiency, such as reducing growth, which reduces the need for phosphorus for the processes that require energy and carbon skeletons, thus, the requirement of phosphorus also reduces [
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The results observed in the present study corroborate those of [
The authors [
The number of Cowpea leaves significantly increased with the phosphorus doses, adjusting to the quadratic regression model, the maximum value (18.32 leaves) was provided by the phosphorus (P2O5) dose of 286.9 mg・dm−3, presenting an increment of 47.16% of production in relation to the absence of phosphate fertilization (
In plants with phosphorus deficiency, there is an accumulation of this nutrient in organic compounds in the roots, which reduces transport to the aerial part and reduces its growth in relation to the root [
leaves causes an increase in the leaf area, which provides greater uptake of solar radiation and, consequently, greater photoassimilates production, allowing good plant development [
The authors [
In other legumes such as java (Macrotyloma axillare), crotalaria (Crotalaria juncea) and pigeon pea (Cajanus cajan), an increase in phosphorus application was also observed compared to the treatment without phosphate fertilization [
The extraction of agronomic species influences the efficiency of phosphorus fertilization [
The chlorophyll content in the Cowpea bean plants, as a function of the phosphate fertilization (P2O5), was adjusted to a quadratic model of regression as the maximum chlorophyll index of 54.33 was observed in the phosphorus dose of 266.12 mg・dm−3, with an increase of 12.9%, when compared to the dose that provided the maximum chlorophyll index in relation to the absence of phosphate fertilization (
The reading of the SPAD chlorophyll index is a method capable of evaluating the nutritional state of the plant, correlating the reading of the chlorophyll meter with the concentration of nitrogen in the plant [
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phosphorus on the nodulation and biological fixation of N2 in cowpea beans, and found a quadratic response for the chlorophyll index with maximum values estimated for the reading of 41 and 56 units at phosphorus doses (P2O5) of 66 and 86 kg・ha−1 for Single Super Phosphate and Triple Super Phosphate, respectively.
Phosphorus coordinates respiration, cell division, formation of proteins and starch. It is a component of nucleotides, such as ATP (adenosine triphosphate) that serve as the plant’s main energy source. This energy is used in the transport of assimilates, energy storage and transfer, cell division, cell growth, and the transfer of genetic information [
The authors [
The diameter of the cowpea bean stem as a function of the phosphate fertilization was adjusted to a quadratic regression model with the largest diameter of 4.75 mm observed in the phosphorus dose (P2O5) of 307.6 mg・dm−3, with an increase of 20% when compared to the dose that provided the largest stem diameter in relation to the absence of phosphate fertilization (
The authors [
The results of the present study corroborate with the findings of other authors [
The diameter of the stem is a very important variable, since the reduced growth in young plants and the production of thin (non-woody) stems are characteristic of phosphorus deficiencies in the plant [
The initial development of the cowpea bean cultivated in the Brazilian Cerrado Oxisol was significantly influenced by the Bayóvar natural phosphate fertilization with the best phosphorus (P2O5) doses in the range of 200 to 350 mg・dm−3.
The study proves that the use of a natural source of phosphorus as an alternative for phosphate fertilization, promoted significant influence on variables important for the good development of the studied crop.
Bonfim-Silva, E.M., Soares, D.C., Silva, P.C.L., Damasceno, A.P.A.B., da Silva, T.J.A. and Sousa, H.H.F. (2018) Initial Development of Cowpea Bean Fertilized with Natural Phosphate in the Brazilian Cerrado Soil. American Journal of Plant Sciences, 9, 1381-1390. https://doi.org/10.4236/ajps.2018.97100