Influence of phosphorus on initial growth and production of fresh biomass of

. ABSTRACT

Aims: To evaluate whether the initial growth and production of green biomass of the species juncea L. and ensiformis (L.) DC. are influenced by phosphate fertilizer. Study design: A completely randomized design was used in a scheme 05 treatments x 02 cultures, with 3 replications, totaling 30 vessels in the experiment. Place and Duration of Study: Forest nursery the Federal University of Campina Grande, campus of Patos-PB, between April 2018 and May 2018. Methodology: The treatments consisted of two legumes (C. juncea and C. ensiformis) and -1 five doses of phosphorus (00-50-100-150-200 mg kg of P2O5) through Simple Superphosphate. Fortnightly measurements of height and diameter were performed for 60 days. Fresh biomass of the shot and root was obtained at the end of the evaluations. Results: There is a higher growth in height for individuals of C. ensiformis when cultivated in doses of 150 mg kg-1, with an average of 30.68 cm. For C. juncea, the treatments were similar. For the stem diameter, there was significant interaction (p <0.05) only for C. juncea, in which, unlike the results obtained for height, this variable grew linearly with increased phosphorus doses. Regardeless of the P doses fresh biomass production of C. ensiformis was higher than to C. juncea. When analysing the unfolding unfolding of P at each legume level, there is an influence of nutrient levels only for C. ensiformis, with higher total biomass -1 production and when cultivated with 100 mg kg of P2O5. Conclusion: Regardless of the cultivated species phosphorus influences the initial growth and production of fresh biomass. In general, it is recommended to cultivate the legumes -1 studied with doses of 100 mg kg of P2O5 through simple super phosphate for a higher production of total fresh biomass. Keywords: Irrigated Perimeters; Recovery of Degraded Areas; Sustainability; Green Manure; Crotalaria juncea; Canavalia ensiformis.

1. INTRODUCTION

The implementation and development of irrigated agriculture in the country is a common and growing practice, but when performed inadequately it promotes several environmental impacts, especially those related to the salinity and sodicity soil [1, 2]. Most of these problems occur in arid and semi-arid regions, because in addition to most agricultural activities being irrigated, annual rainfall does not ensure the washing of mineral salts accumulated in the soil [3, 4].

According to Lima Jr and Silva [5] in the semi-arid region of northeastern Brazil, the highest incidences of areas with salinization are concentrated in the most intensively cultivated lands with the use of irrigation, in the so-called Irrigated Perimeters. Over the years, these areas tend to be abandoned due to reduced soil fertility and agricultural productivity.

It is important to study techniques that improve the chemical, physical and biological properties of the soil, and consequently raise the productivity of the species cultivated there.

Siqueira et al [6] also comment on the need for intervention through conservation practices and Nogueira et al [7] mention green manure as one of the most prominent practices.

Green manure is a vegetative practice that consists of incorporating of non-decomposed material into the soil. It is considered a sustainable option for the reestablishment of soil conditions, because in addition to improving the properties of the soil, it provides nutrients to , assists in water retention and also reduces the use of chemical fertilizers [8, 9, 10].

Legumes are the most used groups of plants used when working with green manure. According to Massadah et al [11] these species provide several benefits to the soil, such as for the cultivated species, in general they are able to perform the biological fixation of N2 through nitrogen-fixing bacteria associated with its root system. Among the numerous species that can be used as green fertilizer, Crotalaria juncea L. and Canavalia ensiformis (L.) DC. has been standing out.

According to Araújo [12] C. juncea is an exotic species of Asian origin, of annual cycle, shrubby legume and belonging to the family , Faboideae (Papilionoideae). Garcia et al [13] comment that the species stands out for its rapid growth and easy adaptation to adverse conditions, besides its great nitrogen-fixing potential.

C. ensiformis is a legume used under various edaphoclimatic conditions, being adapted to regions of arid and semi-arid, or even tropical. With great potential for biomass and nitrogen supply, this species is still widely used in consortia with other crops. Gebauer [14] also comments that the species also has properties used in the control of phytopathogens present in the soil.

Raij [15] explains that phosphorus (P) is one of the macronutrients with low natural availability in most soils from throughout the Brazilian territory, being the nutrient, most used in the fertilization process. In addition to participating in several compounds in the vegetables fundamental to various metabolic processes, in its absence, the plant becomes unable to complete its life cycle. [15].

Considering these characteristics, it is important to analyze these species, as well as their relationship with nutritional sources, in order to provide information about their potential use to reintegrate degraded soils from Irrigated Perimeters to the farm. Based on the above, the study aims to evaluate whether the initial growth and production of green biomass of the legume species C. ensiformis and C. juncea are influenced by phosphate fertilizer.

2. MATERIAL AND METHODS

The experiment was conducted in the forest nursery of the Center for Health and Rural Technology (CSTR) of the Federal University of Campina Grande (UFCG), Patos-PB campus, in an environment with solar reduction factor and protection against rain. According to the classification of Köppen [16] the climate is of type BSh, considered semi-arid hot and dry.

The soil was collected in the irrigated perimeter known as Engenho Arco verde, located in the municipality of Condado-PB. To characterize the physicalchemical attributes of the soil (presented in Tables 1 and 2) samples were collected at a depth of 0-20 cm, sent to the Soil and Water Laboratory (LASAG) of CSTR/UFCG and analyzed according to the methodologies proposed by Raij et al [17] and Amaro Filho, Assis Jr and Mota [18].

Table 1. Chemical attributes of the soil collected in the irrigated perimeter Engenho Arco Verde located in Condado-PB.

pH P Ca Mg K Na H+Al CTC V mg kg-1 ------cmolc dm-3 ------% 6.50 25.40 6.00 3.60 0.38 0.26 1.20 11.44 89.51 *Hydrogenionic Potential (pH), Phosphorus (P), Calcium (Ca), Magnesium (Mg), Potassium (K), Sodium (Na), Total Acidity (H + Al), Cation Exchange Capacity (CTC pH 7.0) and Base Saturation (V%)

Table 2. Physical attributes of the soil collected in the irrigated perimeter Engenho Arco Verde located in Condado-PB.

Granulometry Textural class ------g kg-1------SBCS SAND SILT CLAY 765 137 98 Light sandy *SBCS - Brazilian Society of Soil Science

The of C. juncea (Crotalária) and C. ensiformis (Feijão-de-porco) were provided by the Agroecology course of the Semiarid Development Center (CDSA) of UFCG, Sumé-PB campus, followed by their selection, removing the damaged ones and with injuries. No-tillage was performed, placing five seeds per pot, and after eight days thinning was done, leaving the two plants with greater vigor. The soil was maintained at 70% of the field capacity.

The treatments were composed of two legumes (C. juncea and C. ensiformis) and five doses -1 of phosphorus (00-50-100-150-200 mg kg of P2O5) via Simple Superphosphate (SS). The SS was previously ground and homogenized with the soil. Thus, the IHD (completely randomized design) was used in a scheme 05 treatments x 02 cultures, with 3 replications, totaling 30 vessels in the experiment.

Fortnightly measurements of height and diameter were performed using a ruler graduated in centimeters (cm) and a digital caliper in millimeters (mm) respectively for 60 days. At the end of the evaluations, fresh biomass was obtained from both shoots and root. For this procedure, steel stiletto was used to separate the shoot from the root and trays to separate the soil from the roots. Subsequently, the material was weighed with the aid of the precision electronic scale.

After tabulating the data, statistical analysis was performed using the SISVAR 5.7 software [19]. For the comparative effect of green manure, the Tukey test was applied at 5% and for the dose effect, grade 2 polynomial regression was applied.

3. RESULTS AND DISCUSSION

There is a higher growth in height for individuals of C. ensiformis cultivated at doses of 150 mg kg-1, with an average of 30.68 cm. When comparing this result with the treatment without the addition of P2O5 (control), a difference of 6.53 cm is observed, indicating that phosphorous is fundamental for the initial growth of this species. There is also a reduction in plant height at doses higher than 150 mg kg-1 (Figure 1), demonstrating the importance of applying correct amounts of nutrients in the soil, because excessive levels in besides

causing problems in plant development, can harm the environment and bring unnecessary economic damage. Coutinho et al [20] also verified a negative effect of the excess availability of P to the Vigna unguiculata (L.) Walp crop.

For C. juncea, the treatments were similar, in which there was a difference of smaller than 3 cm from the dose with the highest mean in relation to the lower. It is also possible to observe a decreasing linear behavior, indicating that the height of the plants decreased with the addition of phosphorus (Figure 1). This result is not expected, since fertilizers are added to the soil in order to improve the development of plants such as providing greater growth in height. In Araujo´s work [21] the importance of fertilization in the initial growth of plants of the species C. juncea was verified, in which, when fertilizing them with sources of organic matter, height and average diameter were greater than those cultivated without fertilization.

CRO FP 35 30 25 y = -0.8674X2* + 5.5442X + 18.883 20 R² = 0.37

15 y = -0.4664XNS + 18.896 Height (cm) R² = 0.40 10 5 0 50 100 150 200 -1 Phosphorus levels (mg kg )

Fig. 01. Average heights of Crotalaria juncea (CRO) and Canavalia ensiformis (FP) as a function of different doses of P2O5 during the 60 days.

For the stem diameter, there was significant interaction (p<0.05) only for C. juncea, in which differently from the results obtained for height, this variable grew linearly with increased phosphorus doses, demonstrating that the increasing fertilization of P2O5 provided lower plants, but of larger diameter. For C. ensiformis the diameter increased to the dose of 100 mg kg-1 decreasing after it, confirming the result visualized for the height variable. It is important to note that the variations between treatments (comparison between the best and worst) did not exceed 1 mm for both species (Figure 2).

For the stem diameter there was significant interaction (p<0.05) only for C. juncea, in which differently from the results obtained for height, this variable grew linearly with increased phosphorus doses, demonstrating that the increasing fertilization of P2O5 provided lower plants, but of larger diameter. For C. ensiformis, the diameter increased to the dose of 100 mg kg-1 decreasing after it, confirming the result visualized for the height variable. It is important to note that the variations between treatments (comparison between best and worst) did not exceed 1 mm for both species (Figure 2).

CRO FP 6

5

4 y = -0.078X2NS + 0.4984X + 3.7014 R² = 0.99 3

Diameter (mm) y = 0.2037X* + 2.2223 R² = 0.87 2 0 50 100 150 200 Phosphorus levels (mg kg-1)

Fig. 2. Average stem diameters of Crotalaria juncea (CRO) and Canavalia ensiformis (FP) as a function of P2O5 doses during the 60 days.

Freitas et al [22] when analyzing the initial growth and biomass of two leguminous species as a source of green manure, among which include the species Crotalaria juncea in addition to Inga heteraphylla, they also found a significant difference for the mean diameter among the respective evaluated species, and at the time C. juncea stood out with higher values (1.15 mm month-1) in relation to I. heteraphylla (0.48 mm month-1), while in the present study C. ensiformis presented mean values higher than C. juncea regardless of treatment. These growth variables are important to be studied, since they directly reflect on the quality of plants. Souto et al [23] comment that height provides a good indicator of crop evolution.

Regardless of the P doses, the total fresh biomass production (MFPA + MFPR) of C. ensiformis (96.82 g vase-1) was higher than C. juncea (76.08 g vase-1), even with its fresh root mass being less than 10 g vase-1 (Figure 3). Heinrichs et al [24] also verified higher green biomass production for C. ensiformis compared to other tested green manure.

100 MFPA b MFR 80 ) -1 a 60

a 40 b Biomass (g vase (g Biomass 20

0 C. juncea Species C. ensiformis

Fig. 3. Fresh biomass from the shoot (MFPA) and root (MFR) of legumes (Crotalaria -1 juncea and Canavalia ensiformis) in g vaso independent of the doses of P2O5 at the end of 60 days. *Means followed by the same letters, do not differ by the Tukey test at 5%.

The addition of biomass in the soil, in addition to improving its properties, leads to the reduction of the use of chemical fertilizers, thus making the system more sustainable. Saturnino [25] rightly comments that the sustainable system increases productivity with input savings. In the work of Collier et al [26] for example, there was a reduction in the use of nitrogen fertilizer when cultivating maize with C. juncea.

When working with green manure, it is also important to study the rate of decomposition of waste, as this directly reflects in the availability of nutrients to crops that will be planted a posteriori. Therefore, Collier et al. [26] found that the residues of C. juncea decompose faster when compared to those of C. ensiformis, leading to a higher productivity of Zea mays.

Even with a lower degree of decomposition, in numerous studies there are the benefits provided by C. ensiformis to the soil. Collier et al [27], when studying Z. mays intercropping with C. ensiformis, verified higher maize production when grown without the legume, but soil fertility was impaired, leading to greater acidification and an increase in the H + Al content, thus confirming the ability of this legume to reduce soil acidity. Heinrichs et al [24] also observed accumulation of some nutrients (N, P, K, Ca, Mg and S) in the soil when using C. ensiformis, even with the influence of green manure on maize grain yield only in the second year of cultivation.

The production of total fresh biomass (MFPA + MFPR) increased up to the dose of 100 mg kg-1 decreasing after it. The same behavior was verified for the aerial part. On the other hand, the biomass of the root part grew linearly as a function of the doses of P2O5 (Figure 4), corroborating the fact cited by Miltran et al [28] of the P stimulate root development in legumes.

100 MFPA MFR a a

) 80 b

-1 b a

60

40 a ab ab ab b

Biomassvase (g 20

0 0 50 100 150 200 Phosphorus levels (mg kg-1)

Fig. 4. Fresh biomass from the shoot (MFPA) and root (MFR) of legumes (independent of species) as a function of P2O5 doses at the end of 60 days. *Means followed by the same letters, do not differ by the Tukey test at 5%.

Nuruzzaman et al [29] evaluating the effect of phosphorus on legumes verified that the presence of the nutrient in the soil provides good results for the dry biomass variable. Fact already mentioned by Sultenfuss and Doyle [30]. Hussain [31], when conducting a review

about effect of phosphorus on legumes, also concluded that these plants are dependent on P content in the soil.

In addition to this macronutrient being important in growth and production, it is still essential in several specific functions in legumes. Such as: help in early maturity, increases the strength of the stem in the vegetative stage [28], assists in fixing nitrogen biology [32, 33], helps in resistance to diseases of the root system [34, 35] and promotes production [36].

Krolow et al [37] when evaluating the effects of phosphate and potassium fertilization on three cold season legumes, concluded that only P influenced the variables studied, including nodulation and the type of nodules, confirming the importance of this nutrient in the process of biological fixation of N. Due of this relationship between P and N in legumes, it is believed that this is one of the reasons they require more P than grasses that depend on fertilizers [30].

When analyzing the unfolding of P within each legume level, there is an influence of nutrient levels only for C. ensiformis, with higher production of total biomass (MFPA + MFPR) and -1 shoot when cultivated with 100 mg kg of P2O5. For Crotalaria juncea even without significant difference between treatments, it is observed that the control provided better -1 values for shoot, while the for the root, stood out when cultivated with 200 mg kg of P2O5 -1 and finally species obtained the highest total production at 100 mg kg of P2O5 (Figure 5).

C. juncea 120 C. ensiformis MFPA a MFR 100 a a a 80 a a a a a a 60 a b ab 40 c bc a a a a a 20

0 0 50 100 150 200 0 50 100 150 200 Phosphorus levels (mg kg-1) Phosphorus levels (mg kg-1)

Fig. 5. Fresh biomass from the shoot (MFPA) and root (MFR) of legumes (Crotalaria -1 juncea and Canavalia ensiformis) in g vaso as a function of P2O5 doses at the end of 60 days. *Means followed by the same letters, do not differ by the Tukey test at 5%.

4. CONCLUSION

Regardless of the cultivated species (C. juncea and C. ensiformis) phosphorus influences the initial growth and production of fresh biomass. For C. ensiformis doses higher than 150 -1 mg kg of P2O5 causes negative effect on the variables studied. In general, it is -1 recommended to cultivate the legumes studied with doses of 100 mg kg of P2O5 via simple super phosphate for a higher production of total fresh biomass.

COMPETING INTERESTS DISCLAIMER:

Authors have declared that no competing interests exist. The products used for this research are commonly and predominantly use products in our area of research and country. There is absolutely no conflict of interest between the authors and producers of the products because we do not intend to use these products as an avenue for any litigation but for the advancement of knowledge. Also, the research was not funded by the producing company rather it was funded by personal efforts of the authors.

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