ISSN 1807-1929 Revista Brasileira de Engenharia Agrícola e Ambiental Brazilian Journal of Agricultural and Environmental Engineering v.25, n.2, p.124-131, 2021 Campina Grande, PB – http://www.agriambi.com.br – http://www.scielo.br/rbeaa DOI: http://dx.doi.org/10.1590/1807-1929/agriambi.v25n2p124-131 The amazonian capim-açú is less nitrogen dependent than antelope grass to produce leaf dry matter1 O capim-açú amazônico é menos dependente de nitrogênio que o capim canarana para produzir matéria seca de folhas Ivo G. R. de Araújo2 , Jairo O. Cazetta3* , Rosane C. Rodrigues2 , Sâmara S. C. Sanchês2 , Clésio dos S. Costa4 & Francisco B. F. de Sousa5 1 Research developed at Universidade Federal do Maranhão, Chapadinha, MA, Brasil 2 Universidade Federal do Maranhão/Centro de Ciências Agrárias e Ambientais, Chapadinha, MA, Brasil 3 Universidade Estadual Paulista/Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal, SP, Brasil 4 Universidade Federal do Ceará/Departamento de Zootecnia, Fortaleza, CE, Brasil 5 Universidade Estadual Paulista/Programa de Pós-Graduação em Agronomia, Jaboticabal, SP, Brasil HIGHLIGHTS: Potential of native species for forage production in Baixada Maranhense. Comparison between the performance of capim-açú (Paspalum plicatulum) and antelope grass (Echinochloa pyramidalis). Capim-açú has a high nitrogen use efficiency under lower N doses compared to antelope grass. ABSTRACT: The Maranhão floodplain is dominated by native grasses like capim-açú (Paspalum plicatulum, Mich.). Due to scarce information on nutrient demands of native species, farmers are replacing native pastures by exotic and potentially invasive species such as antelope grass (Echinochloa pyramidalis, Lam). The aim of this study was to compare the growth of capim-açú and antelope grass, under varying N and K doses, to better understand the potential of capim-açú to be used as forage. The experiment was carried out in pots, consisting of a 2 × 5 × 2 factorial scheme (2 species × 5 N doses × 2 K doses) with four repetitions, in a completely randomized design. The N doses -3 -3 of 0, 50, 100, 150 and 200 mg dm were combined with 10 and 30 mg dm K2O. The capim-açú produces higher leaf to stem ratio aboveground by using lower nitrogen and potassium doses than antelope grass. Leaf, stalk, and total dry matter production of both studied species do not respond to potassium doses. Key words: Paspalum plicatulum, Echinochloa pyramidalis, fertilization, plant growth, potassium RESUMO: Devido à escassez de informações das espécies nativas, as pastagens naturais têm sido substituídas por espécies exóticas e potencialmente invasoras como o capim canarana (Echinochloa pyramidalis). Assim, O objetivo deste estudo foi comparar o crescimento do capim-açú e do capim-antílope, em diferentes doses de N e K, para melhor compreender o potencial do capim-açú para ser utilizado como forragem. O experimento foi conduzido em vasos, em um esquema fatorial 2 × 5 × 2 (2 espécies × 5 doses de N × 2 doses de K) com quatro repetições, em delineamento inteiramente casualizado. As doses de N de 0, 50, 100, 150 e 200 mg dm-3 foram combinadas com 10 -3 e 30 mg dm K2O. O capim-açú produz mais matéria seca de folhas e menos matéria seca do caule acima do solo, utilizando menor dose de nitrogênio, quando comparado ao exótico capim canarana. A produção de folhas, caules e matéria seca total de ambas as espécies estudadas não responde às doses de potássio. Palavras-chave: Paspalum plicatulum, Echinochloa pyramidalis, adubação, crescimento, potássio • Ref. 232114 – Received 12 Dec, 2019 This is an open-access article * Corresponding author - E-mail: [email protected] distributed under the Creative • Accepted 11 Nov, 2020 • Published 07 Dec, 2020 Commons Attribution 4.0 Edited by: Hans Raj Gheyi International License. The amazonian capim-açú is less nitrogen dependent than antelope grass to produce leaf dry matter 125 Introduction Material and Methods In order to withstand growing food demands, food The experiment was carried out under greenhouse conditions production must be increased in a sustainable way; by at the Universidade Federal do Maranhão, in Chapadinha, MA, increasing productivity or by using marginal lands (Pittelkow Brazil (03° 44’ 06” S, 43° 19’ 00” W, at 100 m of altitude), Brazil, et al., 2015; Chaldhary et al., 2018). The Maranhão floodplain in 2015. The soil, and plant seedlings used in this assay were all (“Baixada Maranhense”), Brazil, is a typical boundary area, collected at Ingaí Farm, in Vitória do Mearim, MA (03° 27’ 51” S, located between the Amazonian rain forest and dry savanna, 44° 51’ 47” W), located in the legal Amazon area (Figure 1). characterized by alternating periods of intense rainfall and The soil was classified as a Plinthosol (Plinthaquox), and it flooding with severe dry seasons (Silva et al., 2015; 2019). was collected from the layer of 0-0.20 m, during rainy season, Capim-açú grass (Paspalum plicatulum Mich) naturally where grasses are normally growing. This soil was dried under occurs in the Maranhão floodplain; however, due to scarce room conditions, mechanically homogenized, sieved (mesh of information on nutritional requirements of capim-açú, farmers 5 mm), and characterized following methods described by Raij often replace native pastures with exotic species (Tamele et al., et al. (2001). The chemical characteristics of the soil were: pH 2017) such as antelope grass (Echinochloa pyramidalis Lam). = 4.6, P = 7 mg dm-3, organic matter = 19 g kg-1, S = 5 mg dm-3, -3 -3 -3 Antelope grass is considered an invasive species (López Rosas K = 1.1 mmolc dm , Ca = 21 mmolc dm , Mg = 9 mmolc dm , -3 -3 et al., 2015), that may lead to future environmental problems. H + Al = 22 mmolc dm , Al = 7 mmolc dm , cation exchange -3 -3 Pasture grasses usually are very responsive to N availability capacity = 53 mmolc dm , and sum of bases = 31 mmolc dm , in the soil (Paiva et al., 2012; Costa et al., 2013; Gazola et al., corresponding to a base saturation (V%) of 58%. 2019), and this response can be more evident under suitable A series of 80 identical plastic pots (0.20 m height, 0.20 m K supply (Prajapati & Modi, 2012; Sanchês et al., 2013; Morais average diameter, 0.031 m2 of soil surface area) were filled et al., 2016). In addition, antelope grass plant characteristics with 6 dm3 of the mentioned soil (density = 1.4 kg dm-3). (Clayton et al., 2006) are very different from those of capim- According to the soil analysis, and following recommendations açú (Machado et al., 2013), which may lead to differences in of Cantarutti et al. (1999), liming was not needed because the plant growth responses to N and K fertilization. Moreover, soil V% (58%) was above that indicated for growing grasses -3 some studies suggest that native plants have a series of (50%), and P fertilization was done by applying 15 mg dm -1 characteristics that provide resilience and fast recovery after P (equivalent to 70 kg ha P2O5) as simple superphosphate the drought period (Maranhão et al., 2019), and may have (18% P2O5) which was completely incorporated manually, a higher nitrogen use efficiency compared to exotic species mixing into the soil of each pot separately. Then the soil was (Reed et al., 2011; Shivega & Aldrich-Wolfe, 2017). Thus, the moistened and seedlings were planted. Six individual tillers of hypothesis that capim-açú and antelope grass may respond antelope grass were planted in each pot, while for capim-açú differently to N and K supply was evaluated by comparing the three clumps (containing 10 tillers each) were planted per pot growth of capim-açú to antelope grass, under varying N and/ to compensate for morphological differences among species, or K doses of fertilization. and to culture equivalent seedlings. Figure 1. Location of the Maranhão Floodplain (“Baixada Maranhense”) in the area of Legal Amazon, and in the Maranhão State, Brazil Rev. Bras. Eng. Agríc. Ambiental, v.25, n.2, p.124-131, 2021. 126 Ivo G. R. de Araújo et al. Plants of all experimental units were irrigated daily (to blades were separated into sections of 10 cm length with maintain approximately 70% of maximum soil capacity) and uniform width. Using the measured width and length the area grown under the same conditions until 30 DAP (days after (A) of those leaf sections were calculated, and dry matter (W) planting). At this time, all plants were cut at 10 cm above determined. Total plant leaf area (LA) of each experimental the soil surface to standardize growth and begin treatment unit was estimated by using the formula: LA = LDM ∙ (A/W), applications. in which LA = total leaf area (cm2) of the experimental unit; The experiment consisted of a 2 × 5 × 2 factorial scheme LDM = total leaf dry matter (g) of the experimental unit; A = (2 species × 5 N doses × 2 K doses, respectively). The native area (cm2) of the leaf sections; W = dry weight (g) of the leaf forage species studied was capim-açú (Paspalum plicatulum sections (Sanchês et al., 2013). Mich) in comparison to an exotic species: antelope grass Nitrogen utilization efficiency (NUE) was determined by (Echinochloa pyramidalis Lam). The N doses applied to the soil using the formula: NUE = (DMN - DM0)/N; where: DMN = Dry -3 were: 0, 50, 100, 150 and 200 mg dm (respectively equivalent matter (g per pot) of treatment with N; DM0 = Dry matter (g to doses of 0, 100, 200, 300 and 400 kg ha-1 N, incorporated per pot) of treatment without N; N = nitrogen (g per pot) of in a 0.20 m soil layer) applied in the form of granular urea. that treatment (Cabral et al., 2013). -3 The K doses tested were 10 and 30 mg dm K2O (respectively For leaf area (LA), leaf dry matter (LDM), stalk+sheath -1 equivalent to 20 and 60 kg ha K2O) as KCl.