Period of Weed Interference in Bean With Nitrogen Fertilizer

The competition between weeds and bean plants, mainly by nutrients of the environment, is one of the main causes of low crop yield. Therefore, the objective of this study is to evaluate the effects of nitrogen fertilization on the extension of the period prior to interference (PPI) in common beans, cultivar TAA GOL. Sowing was performed in conventional system. The treatments were divided into two groups: cover nitrogen fertilization (200 kg urea ha) and no cover fertilization. Within each area, we established periods of cohabitation of the crop with weeds from the emergence up to seven times of its life cycle (0-10, 0-20, 0-30, 0-40, 0-50, 0-60, 0-70 days) and a control. The experiment design was randomized blocks with three replicates. Digitaria spp. presented a greater relative importance in both areas, followed by Eleusine indica. The period prior to weed interference (PPI) in the area with nitrogen fertilization occurred up to 46 days after emergence (DAE), and only up to 3 DAE for the area without cover fertilization. There was a 30% decrease in bean productivity by comparing the area with nitrogen fertilization (2,004.79 kg ha) and the area without nitrogen fertilization (1,412.43 kg ha). Therefore, nitrogen fertilization increased crop yield and favored it competitively in relation to weeds by increasing the weed PPI.


Introduction
Brazil is among the world's top three bean producers 3,389 million tons are expected in the 2018 harvest (IBGE, 2018).The mean yield is approximately 1,069 kg ha -1 , relatively low considering the possibility of obtaining an average of 3,483 kg ha -1 .Among the causes of such a low crop yield, weed interference stands out as it may affect bean growth, development and productivity (Patil et al., 2014).Bean yield losses caused by weeds may range from 25% to 77% depending on the crop and the environment (Osipitan et al., 2016).
Competition is the best-known form of direct interference of weeds in agricultural crops, the resources most often leading to competition are nutrients, light, water and space (Pitelli, 1987).There are three important periods of coexistence analyzed by interference studies, as Pitelli and Durigan (1984) have proposed: total interference prevention period (PTPI), pre-interference period (PPI) and critical prevention interference period (CPIP).
The duration of the coexistence period between plants and the season in which competition is established, as well as edaphoclimatic conditions, management techniques, the abundance and distribution of weeds, influence the response of plants to weed interference (Xiao-Yan et al., 2015).The extension of coexistence periods can be affected by several factors, among which there is mineral fertilization, especially nitrogen fertilization, which favors both crop and weed growth (Pitelli, 1987).Among nutrients, nitrogen is required in a greater quantity by common beans.Depending on the cultivar, it has a greater or less capacity of atmospheric nitrogen fixation by the action of N 2 -fixating bacteria existent in the nodules formed in the root system (Bordin et al., 2003).In addition to providing adequate plant nutrition and increasing bean productivity, nitrogen provides the crop with better conditions to compete with weeds.Coelho et al. (2001) reported that nitrogen application resulted in a 50% decrease in weeds, a higher number of pods per plant and a 64% increase in bean productivity.Bressanin et al. (2013), for example, observed that Rubi beans could coexist with the weed community up to 38 days after emergence in an area with nitrogen fertilization.In an area without nitrogen fertilization, this culture could coexist with the weed community only up to 18 days after emergence.This period is called period prior to interference (PPI).

Results
The weed (eudicotyle Asteraceae Convolvul species eac Cyperacea In the area developme were 37.9 The initial (2015).By between 3 crop.Osip DAE.Barroso et al. (2012) obtained a 19% decrease in yield of common beans grown in the spring.

In another
However, many factors may interfere with the period prior to weed interference, such as environmental conditions, weed infestation, weed composition, management practices, soil moisture, soil fertility and plant density (Adigun et al., 2014;Osipitan et al., 2016).Figure 6.Productivity of the common bean TAA GOL in areas without (s/N) and with nitrogen fertilization (c/N) in function of control periods and coexistence with weeds considering a loss of 5%, and determination of period prior to interference (PPI)

Conclusion
The weeds with a great relative importance to the common bean crop 'TAA GOL' were Digitaria spp.and E. indica.
Cover nitrogen fertilization increased bean productivity even in the presence of weeds.It benefited the crop and, consequently, increased the period prior to weed interference (PPI).
Common bean 'TAA GOL' bean can coexist with the weed community for up to 3 DAE (PPI) without decreasing its productivity in areas without nitrogen fertilization and up to 46 DAE in areas with nitrogen fertilization. Figure