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to study the impact of Integrated Nutrient Management on some soil properties and nutrients uptake by red onion (Allium cepa L.) in Moda, Michika, Adamawa state, Nigeria. Soil samples were randomly collected and analysed for pH, EC, organic carbon, organic matter, total nitrogen, available phosphorus before and at the completion of the experiment. Total nitrogen, phosphorus and potassium contents of the onion bulbs were determined. There was an improvement in the fertility status of the soil as a consequence of integrated nutrient management. Combined organic and inorganic fertilizer application influenced the uptake of nitrogen, phosphorus and potassium by red onion. The highest nitrogen, phosphorous and potassium uptake by onions of 0.76, 43.82 and 2.42kgha -1 occurred when all treatments were combined. Uptake of N and K increased as treatment level increased. The P uptake was highest at lower treatment levels and could be linked to sufficiency of indigenous soil P for plant growth resulting in high P uptake with minimal addition of nutrient inputs. Integrated Nutrient Management could be adopted to improve soil fertility status and N, P and K uptake by red onions.

This study was carried out with the aim of assessing the effectiveness of four biochar materials; in reducing nitrate leaching from soils of three different textural classes in the Nigerian Savanna region. Soil samples (0-20 cm depth) were collected from three different soil types and three different locations each in the Nigerian Savanna using stratified random sampling. Two hundred and fifty (250) g of soil samples were amended with 0, 2.5, 5, 7.5 and 10 tonha-1 of Maize cob biochar (MCB), rice husk biochar (RHB), cow dung biochar (CDB) and poultry litter biochar (PLB) and were subjected to laboratory leaching experiment. Sixty (60) ml of nutrient solutions containing 300 mgl-1 nitrate using ammonium nitrate (NH4NO3) was applied to each of the laboratory biochar-incubated soil columns to study biochar effect on nutrients retention and transport. The experiment was laid in a Randomize Complete Block Design (RCBD) replicated three times. Leachates were collected and nitrate concentration was determined using a dual beam UV/VIS spectrophotometer. The data collected were analysed using the Generalized Linear Model (GLM) procedure and the means were separated using Tukey’s honest significant difference (SAS version 9.4). Results obtained revealed that there were no significant differences among the biochar treatments on nitrate leaching from Clay loam. However, highest nitrate leaching from Loamy soil of 30.53% was recorded by the application of 2.5 tonha-1 PLB and was significantly different from the application of 2.5 and 5-ton ha-1 RHB and 5-ton ha-1 MCB. Similarly, highest nitrate leaching from Sandy loam of 32.18 % was recorded by the application of 5-ton ha-1 MCB and was significantly higher than 5.94, 2.40 and 7.12 % recorded by the application of 2.5 and 5-ton ha-1 RHB and 7.5 tonha-1 CDB respectively. Therefore, application of 2.5, 5-ton ha-1 RHB and 7.5 tonha-1 CDB can effectively reduce nitrate leaching from Sandy loam. While 2.5, 5, 7.5 tonha-1 CDB and 2. 5 and 5 tonha-1 RHB reduced nitrate leaching from Loamy soils.

to study the effects of organic materials on phosphorus forms under submerged condition in the soils of Geriyo Irrigation project. Soils were incubated with cowdung and poultry droppings at 5, 10 and 15 tons/ha for a period of 90 days. Soil samples were collected at 30, 60 and 90 after submergence and processed for analyses. Results showed that the soils were slightly acidic, low in total nitrogen, available phosphorus, effective cation exchange capacity (ECEC), and percent base saturation (PBS). Characterized organic materials showed higher N, P, and K contents in poultry droppings while cowdung had higher moisture and organic carbon contents. Irrespective of the type of organic materials, total P, organic P, available P and other forms of P increased significantly (p<0.05) with increasing levels of organic materials in both trials. In the first trial, total P and organic P increased at 60 days of submergence and declined afterwards while available P progressively increased up to 90 days of submergence, saloid P and aluminum bound P progressively decreased up to 90 days of submergence while iron and calcium bound P were highest at 60 days of submergence. In the second trial, total P and organic P progressively decreased with time while available P decreased at 60 days of submergence, saloid, aluminum and iron bound P were highest at 60 days of submergence. This implies that the use of poultry droppings in the soils of Geriyo irrigation project may ensure the supply of phosphorus to sustain rice production despite the seasonal flooding in the area with high risk of iron toxicity/ antagonism.