Yield of Brachiaria in Function of Natural Phosphate Application and Liming in Pará Northeast

Forage plants of the genus Brachiária show excellent adaptation to poor soils with high acidity in the region. They present good response to phosphate fertilization and tolerant to soil with higher humidity. The soils of Amazonia are characterized mainly by high acidity, low availability of phosphorus and high saturation of aluminum. Under these conditions, aluminum tends to fix the phosphorus, making it necessary to apply higher doses to supply the need for fodder, justifying the need to apply corrective acidity material. The objective was to evaluate the pH of the behavior and productivity of Brachiaria brizantha cv. Xaraés by using Arad rock phosphate and limestone dolomite in a yellow Latosol of medium texture collected from the 0-20 cm layer. The treatments were: soil only (T1); soil with the addition of lime (T2); soil with added Arad 30 days before planting (T3); soil with the addition of Arad on planting (T4); soil with the addition of Arad and liming 30 days before planting (T5); and soil with the addition of Arad and liming on planting (T6), distributed in five replications, totaling 30 experimental units. At 45 days of germination, evaluated the plant height (HP) and number of leaves (NL), culminating with the courts to obtain the shoot fresh matter (SFM) and dry matter (FDM), the other cuts made every 30 days. pH variations responded positively to the treatments using lime to increase the pH to levels close to 6.5. For HP variables, NL, SFM and SDM the highest increases were obtained for treatments under the influence of limestone (T2) and limestone + Arad 30 days before planting (T5). The natural phosphate fertilizer in combination with liming showed significant results for all parameters.


Introduction
Grasses from Brachiaria genus comprise about 90 species of great morphological and phenological variety (Alves et al., 2015).They are mainly used in pasture formation in tropical America and own a position among most planted crops in Brazil, used in all stages of cattle raising (Ferreira & Zazine, 2007).
B. brizantha cv.Xaraés tolerates prolonged droughts, an important feature for regions that go through drought periods, has good recovery after burning and good regrowth ability, is susceptible to frost.It has a good tolerance to the grasshopper, it has more palatability than other brachiaria (Alves et al., 2015).According to Corrêa (2002), it presents excellent adaptation to poor soils with high acidity in the region.However, it presents a good response to phosphate fertilization and has a higher tolerance to humid soils compared to other B. brizantha cultivars (Valle et al., 2004).Nevertheless, Amazonian soils are mostly characterized by high acidity, low P availability and high aluminum saturation.In this situation the plants usually present symptoms of phosphorus deficiency, since aluminum fixes the phosphorus in less Available in soil and root surface, and interferes with the absorption, transport and use of phosphorus, among other essential elements, making it necessary to apply higher doses in order to nutritionally supply the need for forage crops (Costa, 2004).This justifies the need for the application of corrective acidity material, such as lime.Costa et al. (2012), obtained the maximum yield of dry mass when evaluating four different levels of liming, obtained high levels of phosphorus, calcium and magnesium due to limestone levels.
The use of natural phosphates, such as Arad, is an efficient alternative in decreasing the P fixation or deficiency in soils, since these have as main characteristic the gradual solubilization, tending to increase the P availability for the plants with the Time (Kaminski & Peruzo, 1997).
Natural phosphates are derived from ground phosphate rock, which may or may not undergo physical processes of concentration (Fontoura et al., 2010).Guedes et al. (2009) states that reactive natural phosphate is a phosphate of low solubility.However, such fertilizer has been widely used in pasture fertilization, as it is also capable of increasing Brachiaria brizantha fodder production in comparison to sources of more soluble and more reactive P 2 O 5 , such as triple superphosphate, Arad in its composition provides around 30% of P 2 O 5 and 37% of CaO in the soil.
The use of natural phosphates for the purpose of recovery or renewal of degraded pastures has been very promising, some studies have demonstrated positive effect that the use of these natural fertilizers has manifested (Guedes et al., 2009;Teixeira et al., 2014).The objective was to evaluate the behavior of pH and productivity of Brachiaria brizantha cv.Xaraés using Arad's natural phosphate and dolomitic limestone on a medium texture yellow latosol.

Research Methodology
The experiment was carried out in a greenhouse at the Institute of Agricultural Sciences of Rural Federal University of the Amazon UFRA in Belém, PA.

Soil Sampling
The experimental plots were formed with soil collected in the 0-20 cm at an arable layer of a typical dystrophic Yellow Oxisol (Embrapa, 2013), submitted to chemical analysis according to Embrapa (2011).

Soil Analysis
pH was determined every 30 days using a 1:2.5 sol-liquid glass electrode in suspension.The fertilizers used were Urea as nitrogen source, Simple Superphosphate (SFS) and Arad as sources of phosphorus and Potassium chloride as of potassium that were applied to the soil before or after sowing of the grass (Brachiaria brizantha cv.Xaraés), According to the treatments.
As a criterion for the determination of the need for soil correction, a calculation was made for aluminum saturation corresponding to 3 t ha -1 of dolomitic limestone, according to Silva (2003), considering 96% relative total neutralization power (PRNT).Each vessel was 7.5 g according to each specific treatment.
The soil was incubated for a period of 30 days maintaining the humidity near the soil field capacity, with limestone to correct the acidity.Based on the soil analyzes, the fertilization was performed following the recommendation of 100 kg N ha -1 , 80 kg P 2 O 5 ha -1 and 60 kg K 2 O ha -1 (Cravo et al., 2007), which corresponded, respectively, The following quantities; 0.6 g/vessel, 1.00 g/vessel and 0.35 g/vessel.Implantation fertilization was performed in all treatments.In the treatments that were used the Arad, there was no application of the simple superphosphate, being applied 0.6 g/Arad vessel.
Twenty seeds of Brachiaria brizantha cv.Xaraés per pot with 8 L capacity, with germination beginning six days after sowing.In the 15 days after germination, thinning was performed, leaving nine plants per pot.Soil moisture was maintained at 70% of the total soil pore volume by daily weighing of the pots, adjusting the weight with distilled water.
Three cuts were performed to determine the biometric variables plant height (HP), number of leaves (NL), shoot fresh matter (SFM) and shoot dry matter (FDM).The first cut occurred at 45 days after germination, the second 30 days after the first and the third 30 days after the second, agreeing with the recommendations of the main seed suppliers of Xaraés, which affirmed the ideal period of 25 to 30 days of rest .
The SFM was determined by weighing the fresh material at the time of plant cutting, cutting was performed at 6 cm from the soil.Then, the material was packed in paper bags and fed to the forced circulation air oven at 65º until constant weight was reached in 72 hours, obtaining FDM.
The HP wa leaf; The N presented analysis o package S

Soil Ch
The pH be classificati exception and T3) in (T5).Benett et al. (2009), evaluating the effect of different doses of phosphorus in the form of natural phosphate Arad in the production of dry mass of Brachiaria brizantha cv.Marandu observed that the increment of the phosphorus doses increased the dry mass and pasture height of Brachiaria brizantha cv.Marandu.Guedes et al. (2009) evaluating the growth of Brachiaria brizanta Stap.Cv Marandu on different doses of the natural phosphate Arad and triple superphosphate, found that the doses of natural phosphate had a significant effect under the variables of dry mass of shoot and root, besides the number of tillers.These data collaborate with Bonfim- Silva et al. (2012) that verified changes in the morphological and productive characteristics of the Marandu grass when they were submitted to increasing doses of natural reactive phosphate.
In this work, it was verified that liming was able to increase both dry and fresh mass production, besides reducing soil acidity and providing Ca and Mg to the plants.Therefore, these benefits have resulted in higher yields of Xaraés grass compared to plants under acid soil conditions in the control treatment (T1).In general, the forage production was significantly higher in the first cut with successive reductions observed in the other cuts, probably due to the absence of nutrient replacement, since the Xaraés grass production was verified only with The application of the fertilization of foundation, in a different situation the other cuts could present considered additions in prod.

Conclusions
Natural Arad phosphate increased soil pH, which was more evident when combined with lime, favoring plant development.
Correction of soil acidity and fertilization with natural phosphate should be antecedent to the planting for the greater forage production of Brachiaria brizantha cv.Xaraes.