Productivity and nutrient extraction by Paiaguás palisadegrass, single and intercropping with pigeon pea, submitted to doses of nitrogen

The objective of this work was to evaluate the productivity and extraction of macronutrients by Urochloa brizantha cv. BRS Paiaguás ( Syn . Brachiaria brizantha cv. BRS Paiaguás) single and intercropped with pigeon pea ( Cajanus cajan cv. BRS Mandarim), subjected to four doses of nitrogen applied in topdressing (0, 80, 160 and 240 kg ha -1 ). The experiment was carried out in São Luís de Montes Belos, GO, in soil classified as dystrophic red latosol, under Cerrado conditions. Plant height and dry mass of pigeon pea, plant height, number of tillers, dry mass, and macronutrient extraction by Paiaguás palisadegrass were evaluated. Higher mass production was observed in the pasture intercropped with the legume, requiring a lower amount of N. Based on the results exposed, the cultivation of Paiaguás palisadegrass reaches higher productivity when intercropped with a legume such as pigeon pea, in addition to providing greater efficiency in the use of nutrients such as N, P and K. Nitrogen fertilization has a negative influence on the production of dry mass and height of pigeon pea plants

Palavras-chave: adubação nitrogenada, consórcio, fixação biológica de nitrogênio The degradation of areas with pastures is still a major problem found on properties in Brazil, an obstacle faced by livestock that directly and negatively affects the animal production chain (Kichel et al., 2011).According to MapBiomas (2020), the area with pasture in Brazil is Arq.Bras.Med. Vet. Zootec., v.74, n.6, p.1151-1160, 2022 soil fertility restoration are the main tools to reverse a reality that is still intrinsic in some properties (Cruz et al., 2021).Nutrient replacement via fertilization is the conventionally established technique for supplying nutrients, making up one of the main forms of availability of these elements.Moreover, nitrogen fertilization, especially of grasses, is considered essential, as nitrogen (N) is directly related to the productive capacity and nutritional characteristics of the pasture (Domingues et al., 2021).
However, nitrogen fertilization requires a significant resource demand, since conventional fertilizers used as sources of N are expensive and vary according to the international market, and this can influence their use.Nitrogen fertilization can be responsible for up to 80% of the cost with topdressing fertilization and is the main component of expenditure on pasture maintenance and the most limiting one (Cabral et al., 2021).Thus, the adoption of more efficient production techniques and the replacement of conventional fertilization are considered wellregarded practices, with the aim of reducing costs and maintaining satisfactory productivity results.
An alternative to minimize these costs is the use of legumes in intercropping with grasses, with the objective of enriching the medium with N through biological fixation, and as a highlight, pigeon pea (Cajanus cajan), which can produce expressive amounts of mass and still with high concentrations of N in the aerial part of the plant (Cavalcanti et al., 2021).
Considering the benefits of intercropping between grasses and legumes, Urochloa brizantha cv.BRS Paiaguás (Syn.Brachiaria brizantha cv.BRS Paiaguás), which is characterized by developing in soils of medium fertility, adapting well to integration systems and standing out for its productive potential during the dry period (Pereira et al., 2017;Euclides et al., 2016), has important characteristics for its wide use in the Midwest, it is an option of choice to work in a intercropping or exclusively.
The objective of this work was to evaluate the productivity and extraction of macronutrients by single Paiaguás palisadegrass and intercropped with pigeon pea, subjected to nitrogen doses.

MATERIAL AND METHODS
The experiment was carried out in Universidade Estadual de Goiás, West Campus of São Luís de Montes Belos, GO (16° 32' 30" S,50 o 25' 21" W and 569 m).The region has an Aw climate according to the Köppen classification, with an average temperature of 23.5 o C and an average annual rainfall of 1785 mm, concentrated between the months of October and March (Alvares et al., 2013).
The experimental design used was randomized blocks in a 2x4 factorial scheme, with four replications.The treatments consisted of two types of pasture (grass and grass + pigeon pea) and four doses of N applied in topdressing (0, 80, 160 and 240kg ha -1 ).Nitrogen fertilization was divided into three seasons during the rainy season, right after the evaluation and lowering of the forage.
The soil of the experimental area is a dystrophic Red Latosol (Santos et al., 2018) and is inserted in a smooth wavy relief.The soil of the tested area has the following initial characteristics: pH (CaCl 2 ) of 5.1; 30 g dm -3 of M.O.; 4 mg dm -3 of P (resin); 32; 1.3; 32 and 6 mmolc dm -3 of H+Al, K, Ca and Mg, respectively; base saturation (V%) of 55%.Soil granulometric composition was 260, 450 and 290g kg -1 of sand, clay, and silt, respectively, for the 0-0.20m layer.
The pasture was established in November 2015: The grass was sown in rows and pigeon pea between the rows, in the amount of 10 seeds per meter.The experiment comprises the second cycle of forages, where a new sowing of pigeon pea was carried out between the rows, in the respective treatments, with 10 seeds m -¹ and the N doses were reapplied.
The evaluation periods were as follows: January, February, April, and June 2017.For pigeon pea, the stand, number of plants m -2 ; plant height and shoot dry mass.The stand was determined by counting all plants in the useful area of each plot.The height of plants was obtained, measuring from the ground level to the insertion of the highest leaf, and the dry mass of the aerial part, by randomly collecting 10 plants per plot, with a cut starting at 0.30 m from the soil surface.
In Paiaguás palisadegrass, plant height, tiller density, shoot dry mass and nutrient extraction were determined.The height of the plants was determined using a tape measure with the aid of a leaf.This variable was measured from the ground level to the highest leaf, in five points of the useful area of each plot.
The measurements of tiller density were carried out with metal frames measuring 0.25 m 2 (0.5x0.5).These squares were allocated at points representative of pasture conditions (average height) at the time of sampling.With the data obtained from the count of tillers present in the area of the metal frame, the density of tillers m -2 was extrapolated.
To determine the productivity, the forage plant was collected with the aid of an iron structure measuring 1.0x0.30mand cut with steel scissors at a height of 0.15m from the soil surface.Then the material was weighed (fresh mass) and only one sample was placed in paper bags and dried in a circulation oven and forced air renewal for 72 hours at a temperature of 65°C.
After this period, the dry mass of the sample was determined.After drying, the samples were ground and sent to the laboratory for the determination of nutrients according to the methodology described by Malavolta et al. (1997).Nutrient extraction was calculated by multiplying the dry mass of the aerial part of the forage (kg ha -1 ) by the nutrient content (g kg -1 ), considering the mean corresponding to the four cuts performed.
The data obtained were subjected to an analysis of variance.The means from the intercropped treatments were compared using Tukey's test (DMS) at the 5% probability level, and the effects of N rates were evaluated by regression analysis using the magnitude of the regression coefficients (significant at 5% probability) as a criterion for the choice of the model.The software Sisvar version 5.6 (Ferreira, 2019) was used for statistical analyses.

RESULTS AND DISCUSSION
The doses of N applied in topdressing had a negative influence on the accumulated productivity of pigeon pea intercropped with Paiaguás palisadegrass.The effect was linear decreasing with the highest response when N was not applied (Figure 1).Bessa et al. (2018) in the same area with no history of legume cultivation found that pigeon pea intercropped with corn and grass responded up to the estimated dose of 166kg ha -1 of N, demonstrating that biological fixation was not sufficient to meet the plant's demand.In the second experiment, pigeon peas were replanted in the same area, with the addition of N left in the soil by the decomposition of the crop residues that remained from the previous crop cycle.
There is evidence showing the inefficiency of nitrogen fertilization in legumes (Martha Júnior et al., 2007;Dent and Cocking, 2017), since this group of plants can meet the demand of N by biological fixation (Boddey et al., 2020).
Pigeon pea dry mass production had an average stand of 71,400 plants ha -1 was 9215 and 6935kg ha -1 of DM for the doses, 0 and 240kg of N ha -1 , respectively.Spósito et al. (2018) found lower results in the productivity of pigeon pea Cajanus cajan cv.BRS Mandarim, but similar behavior, in which the treatment that did not receive fertilization expressed higher values of phytomass 5290kg ha -1 of DM while the treatments that received chemical fertilization with Simple Super Phosphate and organic fertilization with cattle manure produced 4740 and 4090kg ha -1 .Neres et al. (2012), when evaluating the cultivation of Pigeon pea cv.Super N single and intercropped with BRS Piatã and Tifton 85 grasses during three cuts, observed accumulated productions of 9380, 9907 and 9613kg DM ha -1 , respectively, these values close to those found in this experiment (Figure 1).Regarding the height of pigeon pea plants, there was an effect of N doses only on the 3rd and 4th cuts (Table 1).In the 3 rd cut, this effect was linear decreasing, in which the greatest height was expressed at the dose of 0 kg ha -1 of N with 140.6cm.In the 4 th cut, the response was quadratic, with a greater height of 82.25cm also at the dose of 0kg Nha -1 .Plant height had a similar effect on dry mass production, in which treatments that did not receive nitrogen fertilization expressed higher values, thus demonstrating positive effects of biological fixation, to supply the plant's needs.Bomfim-Silva et al. (2014, 2016) both with the culture of Cajanus cajan cv.Mandarin at 72 days of single cultivation, observed plant heights with 62.82 and 100cm, respectively, the same cultivar, in similar edaphic conditions, although in single system they exposed values close to the observed.In the first evaluation, there are low heights of pigeon pea, with an average of 35.40cm, which can be explained by the slow initial growth (Reddy et al., 2016), and by the effect of competition between plants, considering that the Guandu was introduced in the area with the pasture already installed.According to Silva et al. (2020), there is an increase in intra-specific competition, associated with the presence of larger plants in the intercropping, which reduces the availability mainly of solar radiation, in addition to water and nutrients.

Arq
The effect of N doses on grass plant height influenced the 2 nd growth for the averages between C (Paiaguás palisadegrass) and C+G (Paiaguás palisadegrass + pigeon pea)) with quadratic behavior and the estimated dose of 125kg ha -1 of N providing the greatest height and in the 3rd growth period, an effect was observed only for single grass, with an increasing linear behavior (Table 2).Expected behavior for grass, since the effect of N on grasses is proven to be beneficial and may have a positive effect of N doses on the variables of plant mass and height productivity, as highlighted by studies (Canto et al., 2013;Gbenou et al., 2018;Leite et al., 2019).To produce dry mass of Paiaguás palisadegrass, there was a significant interaction between the intercropping and N doses in the first cut and in the accumulated (Table 3).For the second and third cuts, there was an effect of N doses, and the response was linear for the means between exclusive pasture and intercropped pasture; however, in the fourth cut, which corresponds to the dry period, there was no effect of any of the treatments (Table 3).In the third cut, in addition to the doses, the averages of the combinations showed a significant difference, where the C+G intercropping was higher in dry matter production in relation to only the grass.
The intercropping of grass with legume provided higher productivity than the single crop and still requiring less N (Table 3), as verified by Pacheco et al. (2011) that the practiced intercropping has a high potential for the accumulation of nutrient-rich mass.It is verified that for the productivity of the accumulated dry mass in the doses of 80, 160 and 240kg ha -1 of N applied in the intercropping C + G provided increases of 3.8, 10.4 and 8.0%, respectively, when compared to the treatment that did not receive N. Bessa et al. (2018) in the same area found that in the off-season, at 72 and 245 days after the corn harvest, pigeon peas reduced grass dry matter by 32 and 18%, respectively, due to competition for space, since after the first harvest of the pigeon pea sprouts appeared, occupying a larger area.The contribution of N in the soil fixed by the legume does not occur immediately and is due to the decomposition of the dry matter that remains in the area.Regarding N doses, in splitting, the effect was quadratic for both C and C+G systems.The effect of N on the increase in pasture mass production is a conventionally established fact, but there is also the knowledge that there is a limit of response to this nutrient by plants (Johnson et al., 2011;Enriquez-Hidalgo et al., 2016;Valkman et al., 2016).
Corroborating the results, Domingues et al. (2021) presented the exclusive Paiaguás grass fertilized with five doses of N 0, 75, 150, 300 and 600kg ha -1 adjustment to a quadratic regression model to produce dry mass.With maximum productivity in the first cycle for the 1 st , 2 nd , 3 rd , and 4 th period of 5449, 6334, 5652 and 3832kg DM ha -1 for doses of 123, 216, 299 and 321kg of N ha -1 , respectively.
As for the tillering of Paiaguás palisadegrass, there was only an effect of nitrogen rates in the 3rd cut, in which the response was linear with the highest density of 750 tiller m -² at the rate of 240kg ha -1 .The intercropping did not influence grass tillering, so there was no limiting effect of the legume on grass propagation in the experimental period (Table 4).(2017).Therefore, in this phase, the number of tillers increases as a function of time due to the need of the plant to establish itself, since by concept the tiller is the unit that forms the pasture, so after the soil cover the tiller population is limited by the area.already occupied, a fact that justifies the non-influence of the tested factors on this variable.
As for the effect of nitrogen fertilization on tillering, Caminha et al. (2010) in a test with Marandu palisadegrass with doses of up to 450kg N ha -1 , concluded that this increases the renewal of tillers, however it does not compromise the number of these as a function of time, a phenomenon that justifies the non-effect of the doses tested in the 1 st , 2 nd and 4 th cuts.
Regarding the extraction of macronutrients, there was only interaction between the sources of variation for N, for P and K there was an effect of the association of doses of N, without interaction, for Ca and S the effect was only of the doses of N and in Mg there was no effect of no treatment (Table 5).
In the extraction of N, in the splitting of doses in the intercropped, there was a quadratic response in the single system, with maximum extraction at the estimated dose of 216kg ha -1 of N, and linear in the intercropped system.The response in P extraction to nitrogen doses was linear, therefore 24kg ha -1 of P with the dose of 240kg ha -1 of N with potential response to higher doses.In K the response to N rates was quadratic, with maximum extraction of 127kg ha - 1 of K at a rate of 232kg ha -1 of N. While in the pasture the highest nutrient extractions occurred in the intercropped with pigeon pea.
The extraction of Ca and S in response to N doses was linear, that is, with maximum extractions of 68 and 23kg ha -1 , respectively, at the dose of 240kg ha -1 , with a margin of response to doses higher than this.
Although N plays an important role in production, the other macro and micronutrients are extracted to sustain the same production, as proven by Primavesi et al. (2004).
In the extraction of N, P and K in which there was greater extraction of these in the pasture intercropped with pigeon pea than in the single one, it indicates the benefits of the intercropping in the cycling of nutrients promoted by the legume through the fixation of N and decomposition of senescent material (Snapp et al., 1998), since pigeon pea has the potential to accumulate about 360, 40 and 324kg ha -1 of N, P and K respectively (Pissinati et al., 2018), this attests to the benefit of the legume use, soil fertility and, consequently, grass development (Hauggaard-Nielsen et al., 2016).

CONCLUSION
The use of pigeon pea in intercropping allowed greater production of dry mass of Paiaguás grass in the third cut, in relation to exclusive pasture.
The Paiaguás + pigeon pea intercropping has a higher volume of P, K extraction and increased the limit of response to N in the extraction of its own.
Figure 1.Accumulated productivity of pigeon pea intercropped with Paiaguás palisadegrass as a function of the application of N doses in coverage.

Table 1 .
Pigeon pea height (cm) as a function of the application of N doses in top dressing, in the four *, ** and ns: significant at 5%, 1% and not significant respectively.F: Fisher's test.R²: coefficient of determination.

Table 2
C: Paiaguás palisadegrass.G: Pigeon pea.*, ** and significant at 5%, 1% and not significant respectively; equal letters in the column do not differ from each other by Tukey's test at 5% probability.F: Fisher's test.R²: coefficient of determination.

Table 3 .
Dry mass (kg DM ha -1 ) production of Paiaguás palisadegrass as a function of intercropping and application of N doses in topdressing, in the four evaluated seasons C: Paiaguás palisadegrass.G: Pigeon pea.*, ** and significant at 5%, 1% and not significant respectively; equal letters in the column do not differ from each other by Tukey's test at 5% probability.F: Fisher's test.R²: coefficient of determination.

Table 4 .
Santos et al. (2016m²)of Paiaguás palisadegrass as a function of intercropping and application of N doses in topdressing, in the four evaluated seasons Paiaguás palisadegrass.G: Pigeon pea.*, ** and significant at 5%, 1% and not significant respectively; equal letters in the column do not differ from each other by Tukey's test at 5% probability.F: Fisher's test.R²: coefficient of determination.It was found that during the establishment of the Paiaguás palisadegrass there was an increase in the density of tillers as a function of the time of culture, according to the work bySantos et al. (2016), Costa et al. (2016)and other cultivars of Urochloa brizantha cv.Marandu by Portes et al.

Table 5 .
Macronutrient extraction (kg ha -1 ) by Paiaguás palisadegrass as a function of intercropping and application of N doses in topdressing Paiaguás palisadegrass.G: Pigeon pea.*, ** and significant at 5%, 1% and not significant respectively; equal letters in the column do not differ from each other by Tukey's test at 5% probability.F: Fisher's test.R²: coefficient of determination.