Objectives: Pesticides are systematically applied in vegetable crops at Nkolo (in Kongo Central province in the western DR Congo) in order to provide crop protection and improve the yield. This study aimed at assessing the knowledges and practices of gardeners in relation to of pesticides use. Methodology and Results : Forty-six gardeners were interviewed. The questionnaire focused on the pesticides types, solution procedures, application rate and frequency, gardener protective equipment, and the pre-harvest intervals. Socio-professional traits of gardeners were also recorded. Majority of gardeners was male (93% vs 7% of women). Pesticides, especially fungicides and insecticides are systematically applied, based on preventive application and generally in 7 (dry season) and 14 (rain season) days of intervals. Depending on the gardener, 1 to 9 pesticides are used per crop cycle. All the pesticides are generally mixed and applied together on the crops using a manual sprayer. Application rate and pre-harvest intervals varied with gardeners. Most of them do not have been trained on pesticide use (83%), do not use protective equipment (72%) and abandon pesticide containers in the field (46%). Conclusion and application of results : Gardeners in Nkolo and surroundings have poor knowledges on pesticides use and do not use it properly. Systematically application of pesticides without proper protective equipment result in regular contact of gardener with pesticides and exposes them to pesticide poisoning. Furthermore, improper pesticides use should increase the risk of pest resistance in the long term use. In order to mitigate the risk of poisoning for gardeners and consumers, and environmental pollution in Nkolo and surroundings, there is an urgent need to promote proper use of pesticides.

Climate variability in DR Congo in general and in the Kongo Central Province in particular is well established. However, rains related to variables such as frequency of rainy days and duration of the rainy seasons was generally very little studied. This study aims to investigate the influence of the climate event on rainfall patterns in the south-western of the DRC. This is firstly to characterize the climate event from the analysis of the air temperature, the frequency of rainy days and duration of the rainy seasons. Furthermore compare the normal monthly rainfall over the period 1962-2012 to clear the behavior of seasonal rainfall patterns. Climate variability is manifested by temporal dynamic regressive temperatures, annual rainfall and a decrease in the number of rainy days. A temperature increase of around 1˚C was observed from 1992 and the thermal peak was recorded in 1994 (>28˚C). The highest rainfall was recorded in 2006 (>2400 mm). These variabilities cause short periods of intense rainfall leading to early droughts of the end of season.

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Les connaissances sur les modes de labour sont nécessaires en vue d’identifier la méthode de labour appropriée pour améliorer le rendement des cultures dans une zone agro écologique spécifique. Cette étude visait à évaluer l’effet des modes de labour sur le rendement et la rentabilité de la culture du manioc (Manihot esculanta Crantz, cultivar “Mayombe”) à M’vuazi. Trois traitements à savoir : labour à plat ou contrôle (T0), labour en billon (T1) et labour en butte (T2) ont été comparés sous un dispositif expérimental en blocs complets randomisés avec 4 répétitions. A la récolte, le nombre des racines tubéreuses commerçables, le rendement en racines tubéreuses, le rendement en pulpe fraîche et le rendement en matière sèche ont été mesurés. L’analyse coût-bénéfice a été appliquée pour évaluer la rentabilité des modes de labour. Le nombre de racines tubéreuses par plante était de 8,7 sous T0, 8,9 sous T1 et 9,6 sous T2. Les traitements T0 et T2 ont donné 40 t ha-1 des racines tubéreuses contre 37,5 t ha-1 sous T1. Le T2 a donné le rendement en pulpe fraîche le plus élevé suivi de T0 et T1 tandis que le rendement en matière sèche était similaire dans tous les traitements. Toutefois, pour tous les paramètres mesurés, l’analyse statistique n’a pas révélé de différences significatives entre les traitements. L’analyse coût-bénéfice a révélé un manque à gagner de 288 pour T1 et 88 $US pour T2 par rapport à T0. Dans les conditions agro écologiques de cette étude, le labour en billon et en butte semblent donc être inopportuns mais nécessitent d’être évalués sur d’autres types de sols et des terrains accidentés.Mots clés : Travail du sol, manioc, rendement, analyse coût-bénéfice, M’vuazi.   English Title: Effects of different tillage modes on yield and profitability of cassava (Manihot esculanta Crantz) at M’vuazi in DR Congo The data on tillage modes are needed in order to identify appropriate tillage methods to improve crops yield in a specific agro ecological zone. Hence, three tillage modes including flat tillage (T0 or control), mound tillage (T1), and ridge tillage (T2) were compared as to their effects on cassava (Manihot esculanta Crantz, “Mayombe” cultivar) yield and related-profitability at M’vuazi in DR Congo. Field layout design was the randomized complete block design with three above-mentioned treatments and four repetitions. Tillage in all treatments was done using a hand hoe. At harvest (11 months after planting), the number of marketable tubers per plant, cassava fresh tubers yield, cassava fresh flesh yield and cassava dry matter tubers yield were measured. Cost-benefit analysis was computed in order to evaluate the profitability of tillage modes types. Tillage modes do not significantly affect cassava yield and profitability. However, the number of marketable tubers per plant was slightly higher under T2 (9.7 roots plant-1 vs 8.7 on T0, and 8.9 on T1). T0 and T2 yielded 40 t ha-1 of cassava fresh tubers yield, and 37.5 t ha-1 on T1 treatment. Cassava fresh flesh yield decreased following this order: T2 (30.3 t ha-1) > T0 (29.1 t ha-1) > T1 (27.3 t ha-1), whereas cassava dry matter tubers yield was similar across treatments. Compared to T0 (control), cost-benefit analysis revealed a shortfall of 288 and 88 USD (US dollars) in T1 and T2 treatments, respectively. We conclude that mound (T1), and ridge (T2) tillages seem to be inappropriate to improve cassava yield in the study area, but need to be evaluated on others soil types and fields on slope.Keywords: Plowing, cassava, yield, cost-benefit analysis, M’vuazi