In this study, we performed a greenhouse experiment to investigate the effect of cow manure biochar on maize yield, nutrient uptake and physico‐chemical properties of a dryland sandy soil. Biochar was derived from dry cow manure pyrolysed at 500 °C. Cow manure biochar was mixed with a sandy soil at the rate equivalent to 0, 10, 15 and 20 t biochar per hectare. Maize was used as a test crop. Results of the study indicated that cow manure biochar contains some important plant nutrients which significantly affected the maize crop growth. Maize yield and nutrient uptake were significantly improved with increasing the biochar mixing rate. Application of biochar at 15 and 20 t/ha mixing rates significantly increased maize grain yield by 150 and 98% as compared with the control, respectively. Maize net water use efficiency (WUE) increased by 6, 139 and 91% as compared with the control, with the 10, 15 and 20 t/ha mixing rate, respectively. Nutrient uptake by maize grain was significantly increased with higher biochar applications. Application of cow manure biochar improved the field‐saturated hydraulic conductivity of the sandy soil, as a result net WUE also increased. Results of the soil analysis after the harvesting indicated significant increase in the pH, total C, total N, Oslen‐P, exchangeable cations and cation exchange capacity. The results of this study indicated that application of cow manure biochar to sandy soil is not only beneficial for crop growth but it also significantly improved the physico‐chemical properties of the coarse soil.

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The number of sensor types available for measuring soil water content has increased but investigations to compare their performance in saline soils needs clarification. In this study the performance of commercially available, low‐cost soil moisture sensors [time domain reflectometry (TDR), PR1 and WET], all measuring changes in the dielectric constant of the soil water, was evaluated under laboratory conditions in a saline sandy soil. The three sensors were also tested in the same sandy soil growing drip irrigated sorghum (Sorghum bicolor L. cv. Moench) in a greenhouse. Plants were irrigated daily with either saline water (ECw: 9.4 dS/m) or fresh water (0.11 dS/m). The volume of irrigation was equivalent to 100% of the pan evaporation. The results showed that measurement accuracy was strongly dependent on the salinity of the soil. The PR1 sensor overestimated volumetric water content (θ) when the salinity level exceeded 4 dS/m [root mean square of the standard error (RMSE) = 0.009 cm3/cm3]. The WET sensor significantly overestimated θ irrespective of the salinity level (RMSE = 0.014 cm3/cm3). The TDR sensor estimated θ with more accuracy (RMSE = 0.007 cm3/cm3) and thus can be considered as more reliable than the other two sensors. The calibrations were strongly affected by the salinity level of the water, so we recommend that calibration equations are modified to take account of salinity.

This study was carried out to evaluate the effect of mycorrhizal inoculation on the growth and nutrients uptake of maize planted in crude oil-contaminated soil. About 10 kg sterilized topsoil was contaminated with Bonny light crude oil (BLCO) at different concentrations: 0, 200, 300, and 500 ml/pot. Maize was sown at three seeds per pot and later thinned to two stands per pot after two weeks. Inoculation in treatments containing AM consisted of 20 g of Glomus clarum. Data on residual TPH content of the soil, plant height, number of leaves, fresh and dry weights, and nutrients uptake were collected at 4, 8, and 12 weeks after sowing (WAS). The 2 x 4 factorial experiment was laid in a completely randomized design and replicated 3 times. The results obtained indicated that AM inoculated maize had higher and significantly (p˂0.05) nitrogen, phosphorus, potassium, calcium, plant height, number of leaves, fresh and dry weights. Significantly (p˂0.05) lower residual TPH content was recorded with treatments inoculated with AM fungi compared to non-AM fungi inoculated treatments. AM colonization resulted in enhanced nutrients uptake thus, improving the physiological parameters of the test crop.

The effects of organic mulching material on soil surface evaporation were studied in Abia State. The objective of the study was to compare impact of mulch materials on saturated hydraulic conductivity and surface evaporation. The organic mulch materials were composted and non-composted Calapogonuim, Chromolena and Panicum spp. The design was randomized complete block design (RCBD). Data generated were statistically analysed. Analysis of variance was used to compare the influence of mulch materials on the measured soil properties and significant means were separated using least significant differences at 5% level of probability. Line graph was used to represent the impact of mulch materials on the surface evaporation. Results showed that saturated hydraulic conductivity of the soils increased significantly (P ≤ 0.05) with the application of the mulch materials. Soil applied with non-composted Chromolena spp. mulch material had the highest saturated hydraulic conductivity (73.00 cm hr-1). Soil surface evaporation varied with both composted and non-composted mulch materials at 3rd and 9th day. The volume of soil moisture lost to the atmosphere was lower in non-composted Calapogonuim mulch material compared with the other mulch materials under study (3rd to 9th day, 3.9 to 11.0 cm3 respectively). Composted and non-composted Panicum mulch was observed to be a more efficient physical barrier to prevent the loss of moisture to the atmosphere as compared to other mulch materials studied. From the present study, it was evident that application of mulch reduced the actual evaporation rates in the initial days after irrigation (coinciding with early periods of plant growth). The water was thus conserved and could be used by the crop subsequently during the later period of its growth.