Non-uniform blossoming due to deficit irrigation is common in perennial crops such as coffee. It usually leads to uneven ripening of fruits and impairs harvesting efficiency and quality of coffee. The effect of different water deficit periods was evaluated on development stage of flower bud at blossoming stages in coffee plantations. We also evaluated the effect of water deficit on growth, productivity, maturation, and physical quality of the bean. Two identical trials were performed on 19-month-old Coffea arabica cultivars (‘Catuaí Vermelho IAC 144’ and ‘Bourbon Amarelo J9’), from June 2008 to July 2009. Irrigation was suspended and resumed at different times (seven treatments) at the pre-flowering stage using a randomized block design with four replicates. The cultivars reached different levels of deficit for the same period of suspended irrigation. In ‘Catuaí’, 60% of the flower buds opened after the coffee plants were exposed to water deficit from early or late June to early September. In ‘Bourbon’, even the longer water deficit period (06/09 to 09/07) did not induce blossoming greater than 20%. Growth was slightly affected during the water withholding period, but not in the subsequent evaluations in October or January. In both cultivars, drought promoted a higher percentage of ripe cherries at harvest than continuous irrigation, regardless of treatment. In conclusion, although blossoming was not a single concentrated event, especially in ‘Bourbon’, withholding irrigation in the pre-flowering stage contributed to uniform fruit ripening in both Arabica coffee cultivars.

Nonuniform flowering leads to uneven ripening of fruits, which impairs harvesting efficiency and the quality of the coffee. The aim of this study was to determine the water deficit level required to break flower bud dormancy of Coffea arabica and to evaluate its effects on gas exchange, photosynthetic pigment levels, coffee yield, and fruit maturation. After a growth period of 18 months in 200 L pots maintained under greenhouse conditions, water deficit treatments were imposed by withholding watering from plants exhibiting at least a 60% rate of "E4 stage" flower buds. When five groups of six coffee plants reached the pre-dawn leaf water potential (Ψwpd) of -0.04, -0.65, -1.43, -1.96, and -2.82 MPa, the leaf gas exchange was measured and leaf disks were collected to quantify the photosynthetic pigment levels, after which, watering was resumed. The rate of opened flowers increased with the reduction of Ypd based on the mathematical model, Y = 67.064 + 20.660 x ln(-Ψwpd). The leaf gas exchange was strongly affected by water deficit levels, without any alterations in the photosynthetic pigment levels. Coffee yield was not affected by the treatments but the ripe stages of cherries increased slightly with the reduction in Ψwpd. The water deficit level applied at the pre-flowering stage determined the percentage of flowering in C. arabica.

The goal of this study was to analyze the response of Arabica coffee cultivars grown under three levels of Bidens pilosa (beggarticks) interference. At 30 days after transplanting (DAT) of 14 Arabica coffee cultivars into 11 L pots, beggarticks was seeded in the pots and soon after emergence, three levels of weed infestation were established: none, low (two plants per pot), and high (five plants per pot). Treatments were arranged in a 14 × 3 factorial scheme under a completely randomized design, with four replicates. Coffee plant growth was evaluated at both weed emergence and blossoming (90 DAT) when the experiment was completed. Regardless beggarticks infestation levels, significant effects of cultivars occurred on almost all the coffee growth variables. Specifically, the Arabica coffee cultivars Arara, Asa Branca, and Bourbon Amarelo exhibited greater values for root, leaf, shoot, and whole plant dry matter when compared with the other cultivars. The Arabica coffee cultivars presented lower leaf area increments, and also lower leaf, shoot, and whole plant dry matter accumulation when grown under either low or high infestation levels (between which there were no statistical differences, p>0.05) in comparison with that under the weed-free treatment. However, there were no significant interactions between Arabica coffee cultivars and weed infestation levels for those crop growth variables. We conclude that all Arabica coffee cultivars tested were equally susceptible to B. pilosa competition in this phase of crop implantation.