Uso de calcário e gesso, seletividade a herbicidas e ação alelopática de extratos vegetais no desenvolvimento inicial do cafeeiro (Coffea arabica L.)

Abstract

The objective of this work was to evaluate the use of limestone and gypsum, selectivity to herbicides and allelopathic action of plant extracts in the early development of coffee (Coffea arabica L.). For this, three experiments were carried out, two in field simulation and one in a greenhouse. The first experiment consisted in the application of increasing doses of limestone and gypsum installed in two distinct periods in a randomized complete block design with four replications in a 4 x 4 factorial scheme, where the first factor was constituted by increasing doses of limestone equivalent to 0, 1, 2, 4 t ha-1 , the second by increasing doses of gypsum equivalent to 0, 300, 600 and 1200 kg ha-1. The experimental plot consisted of a planting of the cultivar IPR 107 in a PVC pipe (vessel) with a diameter of 100 mm and one meter high. In period I, implantation was carried out during the winter-summer period (05/08/2017 to 03/02/2018) and in period II in the spring - autumn period (02/10/2017 to 31/03/2018). The agronomic characteristics evaluated in this experiment were: plant height, stem diameter, leaf area index, leaf dry matter, root dry matter and root length. When analyzing the results of this experiment it is possible to emphasize that plant height was the most responsive variable in environmental conditions, presenting an increase of 6.18 % in period I in relation to period II and that doses of limestone and gypsum did not provide changes in the agronomic variables in both evaluated periods during the six months after transplanting. The second experiment was conducted in the field under a randomized block design with four replicates and in an 8 x 2 factorial scheme. The first factor was constituted by eight types of herbicidal control (Ethyl Chlorimurom, Methyl Metsulfur, Ethyl Carfentrazone, Cletodin, Ammonium Glufosinate and Glyphosate and witnesses with and without weeding) the second factor consisted of two coffee cultivars (IPR 107 and Obatã). In the cultivar Obatã, the application of Chlorimurom ethyl and Metsufuron metil showed the highest amount of root biomass accumulation (8.88 g) followed by the herbicide Carfentrazone ethyl (7.15 g), already with the application of ammonium Glufosinate (non-selective herbicide) and with weeding (6.45 g), a reduction of up to 27.36% in this accumulation was observed. The herbicides Metsulfuron methyl, Carfentrazone ethyl and Cletodin caused the lowest post-emergence phytotoxicity levels, classified as very light, indicating the selectivity of these herbicides, the cultivars Obatã and IPR 107. The third experiment was conducted in a greenhouse with a randomized complete block design with four replicates, in a 7 x 2 factorial scheme. The first factor was constituted by seven aqueous extracts of the vegetal species: The first factor consisted of seven aqueous extracts of the plant species: canola (Brassica napus L.), Crotalaria (Crotalaria juncea L.),Brachiaria (Brachiaria decumbes L.), sunflower (Helianthus annus L.), wheat (Triticum aestivum L. .), lupine (Lupinus albus L.) and water (control). The second factor was constituted by the different botanical parts of the plants (aerial part and root system). After 120 days of application of extracts, the plant height, stem diameter, leaf area index, leaf dry matter, root dry matter and root length were evaluated, being observed that the height of the plant behaved differently in relation to the extracts and the different botanical parts that they constituted them. The extracts produced through the root system obtained averages higher than the aerial part in the order of 103% for plant height variable. In dry leaf matter the botanical part variation factor was statically diferente the extracts constituted by the root portion presented a value of 110% superior to those originating from the aerial part representing an increase of 0.67 g. In the extracts constituted by the root system, the sunflower presented a result (5.70 g) and the crotalaria (7.63) representing a difference between extracts of 133%. The agronomic characters most sensitive to the application of aqueous extracts were plant height, stem diameter and leaf dry matter.