Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Primarily, spatial information allows a potential reduction in herbicide use, when post-emergent herbicides are only applied to field sections with high weed infestation levels. This paper presents a system for sitespecific weed control in sugar beet, maize, winter wheat, winter barley, winter rape and spring barley. The system includes on-line weed detection using digital image analysis, computer-based decision making and GlobalPositioning System-controlled patch spraying. In a 2year study, herbicide use with this map-based approach was reduced in winter cereals by 6-81% for herbicides against broad leaved weeds and 20-79% for grass weed herbicides. Highest savings were achieved in cereals followed by sugar beet, maize and winter rape. The efficacy of weed control varied from 85% to 98%, indicating that site-specific weed management will not result in higher infestation levels in the following crops. Keywords: weed distribution, site-specific weed control, patch spraying, on-line weed detection, decision support systems, crop rotation. GERHARDS R & OEBEL H (2006) Practical experiences with a system for site-specific weed control in arable crops using real-time image analysis and GPS-controlled patch spraying. Weed Research 46, 185-193.

Grain yield often varies within agricultural fields as a result of the variation in soil characteristics, competition from weeds, management practices and their causal interactions. To implement appropriate management decisions, yield variability needs to be explained and quantified. A new experimental design was established and tested in a field experiment to detect yield variation in relation to the variation in soil quality, the heterogeneity of weed distribution and weed control within a field. Weed seedling distribution and density, apparent soil electrical conductivity (EC a ) and grain yield were recorded and mapped in a 3.5 ha winter wheat field during 2005 and 2006. A linear mixed model with an anisotropic spatial correlation structure was used to estimate the effect of soil characteristics, weed competition and herbicide treatment on crop yield. The results showed that all properties had a strong effect on grain yield. By adding herbicide costs and current grain price into the model, thresholds of weed density were derived for site-specific weed control. This experimental approach enables the variation of yield within agricultural fields to be explained, and an understanding of the effects on yield of the factors that affect it and their causal interactions to be gained. The approach can be applied to improve decision algorithms for the patch spraying of weeds.

The assessment of habitat selection and temporal patterns of activity rhythms is paramount for wildlife conservation. Studies on behavioural ecology of wild mammals are particularly challenging in tropical areas, mostly when involving rare or elusive species. Despite being a common species in Italy, the crested porcupine Hystrix cristata is threatened of extinction throughout most of its sub-Saharan range. All available information on the ecology of this species has been collected in Italy, whereas no data is present in the scientific literature on spatiotemporal behaviour of this large rodent in Africa. In this work, we attempted to determine habitat selection and temporal patterns of activity rhythms of the crested porcupine in northern Benin and neighbouring countries, through intensive camera-trapping. We collected a total of 146 records of crested porcupine, 91 in the dry season (October-March) and 55 in the rainy season (April-September). Porcupines used most habitats in proportion to their local availability, while selecting rock outcrop formations (possibly used as shelter sites) and avoiding open areas, wetlands and gallery forests. A mostly nocturnal behaviour was confirmed throughout the year, with some diurnal activity at the start and at the end of the rainy season. The importance of rains in determining birth peak has been also showed, with juvenile individuals always observed at the start and at the end of the rainy season. Full moon always inhibited activity of this large rodent, most likely evolved as an antipredatory behaviour to limit encounters with potential predators (common leopard Panthera pardus, spotted hyaena Crocuta crocuta and honey badger Mellivora capensis) and humans. Poaching pressure towards porcupines in West Africa is strong. Porcupines are killed for the traditional medicine, for their meat and because they are widely considered as a crop pest. This assessment should therefore be used as a basic tool to design conservation plans to preserve this rodent species in its native range.

To improve data availability and exchange in the area of the WAP complex, West Africa’s largest continuous area of reserves, we set up a citizen science project on the iNaturalist platform, allowing contribution of observations, ideally documented by photographs and/or sounds. Along with the project we created a number of online field guides for the local flora. Within only two months, 852 observations of 312 species have been assembled. We expect this dataset to further grow in the future and complement existing data sets from scientific collections and surveys.

Although clear evidence for benefits in crop production is partly missing, several natural compounds and microorganisms have been introduced to the market as biostimulants. They are supposed to enhance nutrient efficiency and availability in the rhizosphere, reduce abiotic stress, and improve crop quality parameters. Biostimulants often derive from natural compounds, such as microorganisms, algae, and plant extracts. In this study, the commercial plant extract-based biostimulant ComCat® was tested in two field experiments with maize in the communities of Banikoara and Matéri in Northern Benin and six pot experiments (four with maize and two with winter barley) at the University of Hohenheim in Germany. Maize was grown under nutrient deficiency, drought, and weed competition, and winter barley was stressed by the herbicide Luximo (cinmethylin). ComCat® was applied at half, full, and double the recommended field rate (50, 100, and 200 g ha−1) on the stressed and unstressed control plants as leaf or seed treatment. The experiments were conducted in randomized complete block designs with four replications. The above-ground biomass and yield data of one experiment in Benin were collected. The biostimulant did not promote maize and winter barley biomass production of the unstressed plants. When exposed to stress, ComCat@ resulted only in one out of eight experiments in higher barley biomass compared to the stressed treatment without ComCat® application. There was a reduced phytotoxic effect of cinmethylin after seed treatment with ComCat®. Crop response to ComCat® was independent of the application rate. Basic and applied studies are needed to investigate the response of crops to biostimulants and their mechanisms of action in the plants before they should be used in practical farming.

Right timing of weed control is one of the most important challenges farmers in North Benin are facing. Weed infestation rates in maize production in the dry savanna zone in Northwestern Benin are often very high causing significant yield losses. The aim of the study was to determine reasons for late weed control in maize, which is the dominating crop in this area. A survey was conducted among 100 representative farmers in Northwestern Benin. Descriptive statistical methods were used to calculate proportion, frequency or mean of socioeconomic data assessed. The descriptive analysis aimed to select relevant variables for regression analysis. Regression models were applied to identify reasons for low weed control efficacy in maize. The results revealed that poor weed control in maize often occurred in small family farms with diverse cropping systems. These famers are often in conflict to control weeds in several crops simultaneously. Weeds are mostly removed by hand-hoeing. Due to their economic situation, they have usually no access to hired labor. Maize yields in the surveyed area could be increased if farmers had access to credit services (1), if farmers would get better recommendations of critical periods of weed control (2) and if more efficient weed control methods would be available to suppress weed populations (3).