Nitrogen Management, Nitrogen Use Efficiency, and Seed Yield and Quality of Creeping Signalgrass

Abstract

Nitrogen (N) fertilization management can affect the seed yield and quality of tropical forage grasses. Studies have shown the effect of N rates on tropical grass seed production, but no study has evaluated the effect of application timing of N on the N use efficiency (NUE) and seed yield and quality of creeping signalgrass [Urochloa humidicola (Rendle) Morrone & Zuloaga, syn. Brachiaria humidicola (Rendle) Schweick.]. Field experiments were conducted over two growing seasons in Santo Anastácio, São Paulo, Brazil, to evaluate the influence of N fertilization timing on plant nutrition, herbage mass, N uptake, NUE, and seed yield and quality of creeping signalgrass ‘Llanero’. The treatments included a control (no N application) and four treatments with N applied at different times (150 kg N ha−1 during the vegetative phase, 150 kg N ha−1 at panicle initiation [prebooting], 100 kg N ha−1 during the vegetative phase plus 50 kg N ha−1 at panicle initiation, and 50 kg N ha−1 during the vegetative phase plus 100 kg N ha−1 at panicle initiation). Topdressed N fertilization increased the concentration of N in the flag leaf by 35.9% (from 12.2 to 16.6 g kg−1) and increased the herbage N uptake by 99.7% (from 72 and 144 kg ha−1). Herbage mass was not affected by topdressed N fertilization. The greatest seed yield (64.2% or 136 kg ha−1 greater than the control, and an average of 22.5% or 64 kg ha−1 greater than the other N treatments) was observed in response to 100 kg N ha−1 applied during the vegetative phase plus 50 kg N ha−1 applied at panicle initiation, which resulted in improved NUE. Seed viability was greater in the treatments where all or most of the N was applied at panicle initiation. In addition, the seed germination percentage was positively affected by N fertilization, regardless of the N application timing.

Effects of nitrogen fertilisation and irrigation on seed yield and yield components of signal grass (Urochloa decumbens)

“…Hopkinson et al (1996) considered that seed weights <450 mg 100 seeds -1 indicate low percentage of mature seeds in signal grass. Other studies have shown that application of N can influence mean seed weight in signal grass (Carmo et al 1988) and creeping signal grass (Urochloa humidicola (Rendle) Morrone & Zuloaga) (Catuchi et al 2017). However, little is known about the physiological basis for these observations.…”

Herbage accumulation, canopy characteristics, and nutritive value of tropical grasses in the Amazon biome

“…Tupi accumulated less leaf mass than other grasses and this did not vary with season, while Marandu and Guará increased leaf accumulation when environmental conditions were more favorable (Figure 1). Tupi also had the greatest stem proportion because of its growth habit, with many tillers resulting in greater herbage bulk density (Catuchi et al., 2017; Kalmbacher, Adjei, Ezenwa, & Martin, 2005).…”

Nitrogen management of forage grasses for nutrition, seed production, and nutrients in residual straw

“…Nitrogen is one of the nutrients that accumulates in high amounts in the aboveground tropical perennial forage grasses (Primavesi et al, 2006;Moreira et al, 2013;Costa et al, 2015). Nitrogen supply to tropical forage grasses increases herbage yield, as well as the yield components (number of reproductive tillers, inflorescence, length, numbers of seed per inflorescence, and seed filling), seed yield (Manarim & Monteiro, 2002;Barth Neto et al, 2010;Canto et al, 2012;Catuchi et al, 2017), and seed quality (weight and germination) (Canto et al, 2012;Catuchi et al, 2017). However, excess N supply or its application at inappropriate development phases can reduce the yield and quality of tropical forage grass seeds (Condé & Garcia, 1988;Barth Neto et al, 2010;Catuchi et al, 2017).…”

“…This occurs because plants allocate nutrients for vegetative biomass production (Condé & Garcia, 1988;Viana et al, 2011;Cecato et al, 2014). Therefore, to increase the production of tropical forage grass seeds, the application of part of N at the beginning of the reproductive phase (after panicle initiation) may be advantageous, since in this phase, the source-sink ratio of the plant occurs, and photoassimilates, which would previously be translocated to the growth of tillers and leaves, are redistributed to the reproductive structures (Condé & Garcia, 1988;Basto, 2014;Catuchi et al, 2017).…”

“…Factors such as species, cultivar, and nutrient availability may influence the aboveground dry matter (DM) production and nutrient accumulation in the DM of tropical forage grasses Moreira et al, 2013;Catuchi et al, 2017). The aboveground residual straw of tropical forage grass seed production, which can reach 15-20 Mg ha -1 (Souza et al, 2006;Catuchi et al, 2017), can be harvested to produce hay for animal feed, avian beds, the production of organic compounds, and burning for energy cogeneration, or it can be left on soil surface, primarily in areas managed in the no-till system for grain crop cultivation (Souza et al, 2006). Therefore, information on the amount of nutrients contained in the aboveground residual straw is essential to adequately manage fertilizer for forage grasses present in the area, as well as for subsequent crops, to maintain the soil organic matter, adequate nutrient supply, and to avoid soil exhaustion in the areas from which residual straw is removed.…”