Does a Specific Location of Composted Poultry Litter in Soil Influence Nutrient Use Efficiency and Vegetable Production? A Mesocosm Experiment

Animal wastes may be promoted as an alternative to mineral fertilizers that remain unaffordable to the overwhelming part of smallholder farmers in Sub-saharan Africa. However for an efficient use, mechanisms that underly their impact on crops should be well understood. This study was conducted in mesocosm to evaluate impacts of two ways of composted poultry litter (CPL) addition on growth and nutrient use efficiency by cucumber. It included three treatments with five-bucket replicates each- Control, CPL applied on soil surface (CS) or buried to 10 cm-depth (CB). Dry CPL was added at the rate of 0.5 kg bucket-1. At harvest, root distribution was examined in the 0-5, 5-10 and 10-20 cm depths. Dry biomasses of roots, shoot and fruits were also determined and allowed for calculation of diverse indexes of biomass allocation (root-shoot ratio, root weight ratio, stem weight ratio, leaf weight ratio) and nutrient use efficiency (factor productivity of the compost, partial factor productivity of nutrients, agronomic efficiency of compost, and apparent agronomic efficiency of nutrients). The results showed that application of CPL led to a significant improvement of all considered parameters except for the leaf weight ratio which was higher in the control (44.1±3.3) than in CS (28.1±1.9) and CB 31.2±3.5). Total lateral root length was significantly higher in CS than in CB (113.5±10.7 cm vs. 75.5±9.0 cm). The number of lateral roots per plant in the 0-5 cm soil layer was higher in CS than in CB (5.4 vs. 1 root plant-1); the reverse was observed in 5-10 cm (1.2 vs. 4.4 root plant-1). Both fresh fruit yield and total dry mass were positively correlated to root attributes. These were themselves negatively impacted by soil acidity. All nutrient use efficiency indexes were higher in CS than CB. The CPL improved the agronomic performance of cucumber particularly when applied at soil surface.