Effects of Coffee Bean Grounds on Urochloa brizantha Growth

The management of invasive plants is strategic for agricultural areas, since these plants lead to a reduction in productivity. Among potential forms of management is the application of coffee grounds, given that the caffeine present in this residue has allelopathic effects. As such, this study’s objective was to evaluate Urochloa brizantha growth and phytotoxicity when administering different doses of coffee grounds before and after emergence. The experiment was conducted in a greenhouse of the Federal University of Lavras. Planting of the invasive species employed 8-liter vases with 50 seeds each. Assays were performed using a randomized block design, with three replicates, in a 4 × 2 factorial scheme. The first factor was coffee ground dosage: 55, 73 and 100 g doses were diluted in 100 mL of water, and each pot received 100 mL of coffee grounds slurry. The second factor was period of application: pre or post-emergence. Evaluated parameters were: plant height; dry shoot mass; phytotoxicity, speed of emergence (SE), and number of emerged plants. We found that pre-emergence treatments significantly reduced the growth of Urochloa brizantha. In respect to the ‘SE’ and ‘number of emerged plants’ parameters, slurry with coffee grounds doses up to 50 g were found to compromise plant emergence. In respect to phytotoxicity percentage, a linear increase was observed according to the increase in sludge dosage. This study concludes that, when applied during pre-emergence and in low concentrations, coffee grounds compromise the growth of Urochloa brizantha.


Introduction
As one of the largest contributors to gross domestic product, Brazilian agriculture has shown satisfactory performance over the years.It is a diversified agriculture, given the continental dimensions of the country and its cultural differences.,However, irrespective of region, one of the prevalent factors of damaged crops is the occurrence of weeds, which competes with agricultural crops for water, light, space, and nutrients (Vasconcelos et al., 2012), besides making it difficult to harvest grains.
Weed is conceptualized in several ways, being the one that presents more practical context, when its occurrence is in undesired place.Among the weeds that occur along with the agricultural crops we highlight Urochloa spp.These plants, when not properly managed, present a great capacity of competition with the agricultural crop, mainly with the crops of group C3.
For the sustainable management of Urochloa spp. it is necessary to associate several control practices that aim to diminish its competitive effect with cultivated plants.This entails the reduction of costs and the use of strategies to minimize the impact of pesticides on the environment through an approach that aims to reduce the resistance of weeds to the application of herbicides of the same chemical group, adding an opportunity to manage these for farmers who do not use agricultural pesticides on crops.
Coffee grounds us the residue of coffee preparation that remains after water is boiled and infused with coffee powder.In its composition it has caffeine, chemically known as 1,3,7-trimethylxanthine, with a C/N ratio of 22/1 and a nitrogen concentration of 2.3% (Nogal et al., 2005;Mussato et al., 2011), which according to these authors can have an allelopathic effect on cultivated species, either by inhibiting seed germination or seedling growth (Chou & Waller, 1980).
Coffee grounds has 0.02 to 0.08% caffeine (Fan & Soccol, 2005), and its composition variates according to the different blends and the quantity of each species of coffee contained in the powder mixture (Torres et al., 2012).
A suggested hypothesis for the allelopathic effect of the sludge refers to the fact that this in nature material needs to be decomposed, otherwise damaging the plants, given the high microbiological activity involved in the decomposition process (Kiehl, 2010).
According to Friedman, Waller (1983), this substance causes a reduction of invasive plants around the coffee plant, possibly associated with caffeine washing of the canopy.However, its use must be controlled, considering the material has organic and inorganic compounds that can be environmental pollutants (Mussato et al., 2011).Cruz (2015), while experimenting with the application of coffee grounds, observed a decrease in lettuce, carrot and spinach growth, revealing that the inhibition of N and P mineralization reduced plant growth, which also may be associated with the presence of caffeine.
Therefore, the objective of this study was to evaluate the growth and phytotoxicity of Urochloa brizantha after application of coffee grounds, pre and post-emergence.

Experiment Location
The experiment was conducted in greenhouse at the Federal University of Lavras (UFLA), in the Department of Agriculture, located at the following geographical coordinates: Latitude 21º14′ S, Longitude 45º00′ W, and average altitude of 920 meters.The climatic classification for Lavras is Cwa, temperate and rainy with a temperature of 22 °C (22.1 °C in February) (Dantas et al., 2007).
Sowing of the weed was carried out in October 2017, using 8 liter pots, which were filled with soil Dystroferric Red Latosol.Fifty seeds of Urochloa brizantha cultivar BRS Piatã were sown in each pot, with a 75% pure live seed (PLS) rate, in five rows with 10 seeds each, at a depth of 2 cm.This species is an erect growth plant that forms clumps, with leaves up to 45 cm in length.Although they have no pilosity, the leaves' upper part is rough and sharp-edged.The plant is perennial, with an, average size and height between 0.85 and 1.10 m.

Experiment Installation
Sowing of the Urochloa occurred 21 days after the pots were filled with soil.The pots were kept in a greenhouse under irrigation, so that the seed bank in the soil could emerge and then be withdrawn.Irrigation was performed using micro-nebulizers.The experiment was carried out using randomized block design (RBD), with three replicates and a 4 × 2 factorial.The first factor was coffee sludge concentration: 55, 73 or 100 g of coffee grounds and a control treatment with no coffee grounds, i.e., pure water application.The different dosages of coffee grounds were diluted in 100 mL of water and a volume of 100 mL of coffee grounds slurry was applied per pot, using a wash bottle.The second factor was the period of application: pre-or post-emergence.The experiment was comprised of 8 distinct treatments and 24 experimental plots.
The coffee grounds were collected from the UFLA cafeteria and, kept at room temperature.Pre-emergence applications, took place one day after sowing, while post-emergence applications occurred 45 days after sowing.The coffee grounds were collected one day before application.The solute and solvent were mixed for one minute, using a blender.As previously noted, 100 mL of the solution was applied to each plot.

Parameters Assessment
Evaluated parameters were: plant height 60 days after sowing (five plants per plot assessed, using a millimeter ruler); dry mass of the aerial part, carried out in a forced circulation air oven at 60 °C until reaching constant weight (weighing done on a precision scale); visual analysis of phytotoxicity using a grade scale from 0 (no damage) to 100 (total destruction) (Rolim, 1989) (carried out by three people, from the average of the evaluators' scores); speed of germination index (SGI) according to Maguire's (1962) methodology (measuring carried out until the seedlings reached germination stability); index of germinated plants, calculated after the seed bank stabilized.
Where, SGI = speed of germination index; N = number of seedlings count; D = numbers of days after sowing when the counting was performed.

Statistical Analysis
For each parameter evaluated in respect to each treatment, analysis of variance and comparison of means (Tukey test at 5% of probability) were performed (qualitative analyzes).Polynomial models were used to assess the effect of in at 5% prob performed

Results
No interac resulted in during pre the first ten The perce probably h index (SG slurryappli It is noteworthy that, regardless of the coffee grounds dosage, this residue interfered with the initial growth of the plants.Therefore, the in natura disposal of this material to aquatic bodies or otherecosystems can compromise plant emergence, aggravating environmental problems.Alarmingly, a 2257 ng/l -1 water a concentration of this compoundwas found in Porto Alegre city (Potrich, 2014).

Conclusions
The growth of Urochloa brizantha in terms of height and dry weight was compromised in preemergence applications of coffee grounds, with a possible residual effect after initial emergence.Lower doses of coffee grounds compromise the emergence of Urochloa brizantha seedlings.Plant phytotoxicity increases along withslurry dosages, possibly influenced by the residual effect of the slurry on the soil; phytotoxicity is therefore influenced by bothpre and post-emergence applications.The coffee grounds present potential for the control of Urochloa brizantha.

Table 1
grounds contained caffeine almost exclusively, which couldhave contributed to the non-germination of the grass colonies.