Field experiments were carried out during the dry seasons in (2012-2013 and 2013-2014) 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.

Phosphorus (P) fertilizers contain cadmium (Cd) as a contaminant at levels varying from trace amounts to high levels and therefore, can be a major source of Cd to agricultural systems. This study was designed to assess the impact on application of Eppawala rock phosphate (ERP) and triple super phosphate (TSP) as P fertilizers and different soil amendments on P and Cd uptake in maize (Zea mays L.). The field trial was carried out at Field Crop Research and Development Institute at Mahailluppallama, Sri Lanka. A randomized complete block design was employed with three replicates as ERP and TSP separately applied with arbuscular mycorrhizal fungi (AMF) and three types of amendments (biochar, compost and dolomite) and the control without adding P fertilizers. Phosphorus content and Cd content of soil, maize roots and seeds were quantified. Results revealed that available soil Cd and total accumulated root and seed Cd amounts were significantly higher in TSP added treatments with and without amendments compared with ERP added soil. Considering soil available P, root and seed P, there was no significant difference observed in different treatments of TSP and ERP added treatments. A similar phenomenon was also observed in growth and yield parameters with both fertilizers added and with the added amendments. There was no colonization of AMF in maize roots in TSP applied soil while 25-60% of colonization was recorded with ERP. Synthetic fertilizer (TSP) must have inhibited the AMF colonization and thereby increasing the Cd content in maize seeds. AMF colonization increased with comparatively low soil available P in ERP added treatments. The results revealed that TSP could be effectively substituted by ERP as a source of P for maize soils. The addition of AMF, compost and biochar further increased the effect.

This study compared the accuracy of various soil phosphorus assessment methods to measure the soil's ability to supply plants with phosphorus over a brief period in the field. Twenty individual soil samples were collected from a standing wheat (Triticum aestivum L) crop at depths ranging from zero to twenty centimeters. An equivalent plant spike sample was also procured from the soil sampling fields. In comparison to the wet acid digestion method used to detect phosphorus in plants, several methods were utilized to assess phosphorus in the soil, including resin extractable phosphorus, AB-DTPA extractable phosphorus, NaHCO3 extractable phosphorus, water-soluble phosphorus in suspension, and paste. The levels of variation and deficiency of phosphorus, which were found by different methods followed different patterns as shown by the fact that, AB-DTPA method finds phosphorus deficiency in 20% of samples while on the other hand, Olsen method finds phosphorus deficiency in 80% of samples. Even with such a small sampling area, none of the procedures showed a significant correlation with any other method that might account for uneven variation among the samples when determined by distinct procedures. However, corrections were observed to a certain degree between ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) extractable and resin, as well as between other procedures and the plant P scale. Both resin and ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA) had a strong relationship with plant phosphorus, with the former showing a significant correlation of 0.48 and 0.21, respectively. Hence Resin and AB-DTPA methods are recommended for the determination of phosphorus under certain soil and plant conditions.