Biomass Yield of Crotalaria Juncea After Thinning and at Varied Sowing Densities in the Coastal Plateau of Piauí State, Brazil

Abstract

-The northern region of Piauí state is an important center of irrigated organic fruit farming, wherein sandy soils with low organic matter content are predominant, besides climate with high temperatures, long periods of water deficit and constant wind. Given this situation, it becomes necessary to investigate alternative management options able to meet the challenges of agricultural productivity. In this context, green manuring becomes an important practice, mainly when using fast-growing species and with great potential for biomass production. Thus, a study was carried out at Embrapa Meio-Norte to measure Crotalaria juncea biomass yield after thinning and at various sowing densities. The evaluated parameters were plant height, stem diameter, number of branches per plant, fresh and dry weight of shoots and roots. The results showed that sowing density had no influence on plant height; however, unthinned plants reached greater heights, which might have been due to reduced competition for light. Thinning had no effect on diameters of plant stem base; on the other hand, lower planting densities promoted larger diameters also due to less competition. Likewise, the number of branches per plant was not affected by thinning, being greater at lower planting densities on account of less competition. Thinned plants achieved higher averages of fresh shoot weight. Nevertheless, shoot dry biomass was greater at higher planting densities. Furthermore, both fresh and dry weight of roots were not influenced by any of the adopted treatments.Key words: Green manuring. Cover crops. Management. PRODUTIVIDADE DA CROTALARIA JUNCEA SOB PODAS E DENSIDADES DE SEMEADURA NOS TABULEIROS COSTEIROS DO PIAUÍRESUMO -Na região norte do Estado do Piauí, concentra-se um importante polo de fruticultura orgânica irrigada, onde há predomínio de solos com textura arenosa e baixos teores de matéria orgânica, além de clima com temperaturas elevadas, com longos períodos de déficit hídrico e vento constante. Diante desse quadro, faz-se necessário investigar formas alternativas de manejo, capazes de responder aos desafios da produção agrícola. Portanto, é relevante destacar a utilização da adubação verde, principalmente com espécies de crescimento rápido e com bom potencial de produção de biomassa. Com o objetivo de avaliar a produtividade da C. juncea. sob a influência de podas e densidades de semeadura, foi instalado um ensaio na Embrapa Meio-Norte. Foram avaliadas a altura das plantas, diâmetro de caule, número de ramos por planta, massa fresca e seca da parte aérea e das raízes. A densidade de semeadura não influenciou na altura das plantas, no entanto, observou-se maior altura das plantas que não foram podadas, provavelmente, em função da menor competição por luz. O diâmetro do colo das plantas não foi influenciado pelas podas, porém, foi maior na menor densidade de plantio, em função da menor competição. O número de ramos nas plantas também não foi influenciado pelas podas, entretanto, foi maior quanto menor a densidade de plantio, possivel...

Biomass of Crotalaria juncea as a function of plant densities in the semiarid region of Northeastern Brazil

“…In the study by Pereira et al (2005), the highest SDM is obtained both by increasing the number of plants in the row (5, 10, 20 and 40) as well as by decreasing the row spacing (120, 60 and 30 cm). As plant densities tested by Eiras and Coelho (2012) result in similar dry mass per plant, the increase in plant density per area is determinant for the increase in SDM, as stated by Teodoro et al (2016). Similarly, in our study the SDM increased with higher plant density per area, but SDM per plant decreased.…”

“…This result is corroborated by other studies, like that of Eiras and Coelho (2012), who observe an increase in SDM as plant density increased from 20, 30, 40, 50 and 60 plants m -2 , keeping 50 cm between rows. With the same spacing, Teodoro et al (2016) obtain an increase in SDM with higher densities of 20, 40 and 60 plants m -2 . In the study by Pereira et al (2005), the highest SDM is obtained both by increasing the number of plants in the row (5, 10, 20 and 40) as well as by decreasing the row spacing (120, 60 and 30 cm).…”

“…Among the benefits of biomass added to the soil by green manures are weed control, maintenance of soil moisture and temperature, the promotion of biological diversity, and remediation of degraded areas. An increase in SOM improves soil aggregation, which benefits soil density, soil porosity and water infiltration, while soil cover slows rainwater runoff, reducing soil and water losses by erosion (Espíndola et al, 2005;Teodoro et al, 2016;Pereira et al, 2017).…”

“…Sunn hemp is characterized by rapid growth, tolerance to water stress, low soil fertility requirements, and it is able to fix from 78 to 183 kg ha -1 of nitrogen into nitrogen oxides that produce ammonia, nitrites and nitrates. In addition, it can control nematodes and weeds (Espíndola et al, 2005;Silva et al, 2007;Teodoro et al, 2016;Facco et al, 2018). Sunn hemp is indicated for remediating degraded areas, including compacted soils (Pacheco et al, 2015;Pereira et al, 2017).…”

“…Additionally, nitrogen accumulation in the shoots accompanies an increase in biomass (Pereira et al, 2005). Perin et al (2010) and Teodoro et al (2016) show that phosphorus and magnesium accumulation by sunn hemp is more influenced by the amount of biomass produced than by the content of these nutrients in the biomass, while calcium accumulation is influenced by both higher biomass production and its higher content in biomass.…”