Asian Soil Research Journal

Aims: Direct methods of measuring saturated hydraulic conductivity (K_s), either in situ or in the laboratory, are time consuming and very expensive. Several Pedotransfer functions (PTFs) are available for estimating K_s, with each having its own limitations. In this study, the performances of four popular PTFs were evaluated on different soil classes in the semi deciduous zone of Ghana. The PTFs considered herein were Puckett et al. (1985), Campbell and Shiozawa (1994), Dane and Puckett (1994), and Ferrer-Julià et al. (2004). In addition, five local data derived PTFs were used to study the possibility of using local datasets to validate PTF accuracy.

Materials and Methods: A total of 450 undisturbed soil cores were collected from the 0 – 15 cm depth from three benchmark soils, namely, Stagni-Dystric Gleysol (SDG), Plinthi Ferric Acrisol (PFA) and Plinthic Acrisol (PA). The K_s of samples were measured by the falling-head permeameter method in the laboratory. Sand, silt and clay fractions, bulk density, organic matter content, and exchangeable calcium and sodium were measured and used as input parameters for the newly derived PTFs. Accuracy and reliability of the predictions were evaluated by the root mean square error (RMSE), coefficient of correlation (r), index of agreement (d), and the Nash-Sutcliffe efficiency (NSE) between the measured and predicted values from both tested and newly derived PTFs. The relative improvement (RI) of the newly derived PTFs from this study over the existing ones were also evaluated.

Results: The newly derived PTFs in this study had higher prediction accuracy with r, d, RMSE and NSE ranging from 0.80 – 0.99, 0.79 – 0.94, 0.14 – 1.74 and 0.84 – 0.98, respectively, compared with 0.32 – 0.45, 0.27 – 0.50, 4.00 – 4.90 and 0.41 – 0.47 for the tested PTFs. The relative improvement of the newly derived over the tested PTFs ranged from 56.50 – 95.71% in the SDG, 70.73 – 96.89% in the PFA, and 65.37 – 95.81% in the PA. Generally, RI was observed to be highest for Model 1 in the SDG, and Model 4 in both PFA and PA, and lowest for Model 5 in all three soils. It was observed that the inclusion of exchangeable calcium and sodium as predictors increased the predictability of the newly derived PTFs.

The combine use of dry cocoa bean testa ash and poultry droppings for the improvement of soil fertility, maize growth and yield was studied on an Alfisol south western Nigeria, located at Joseph Ayo Babalola University Ikeji-Arakeji, Ilesa Osun State, Nigeria. Research farm from April to July 2018 and from August to November 2018. Four treatments of poultry droppings (PD) at 5 tones  ha^-1, cocoa bean testa ash (CBTA) ash at 5 tones ha^-1, mixture of poultry droppings and cocoa bean testa ash (PD + CBTA) at 2.5 tones ha^-1 each and control (C) were used in a Randomized Complete Block Design (RCBD) with three replications. The study showed that organic manure is a valuable fertilizer and can serve as a suitable alternative to inorganic fertilizer in the south western Nigeria especially, CBTA that has higher concentration of potassium (K) and organic carbon (OC). Poultry droppings (PD 2.5 tones ha^-1) treatments plus cocoa bean testa ash (CBTA 2.5 tones ha^-1) produced higher values for plant height, leaf area, chlorophyll, leaf area index, plant diameter, cob length, cob diameter and grain yield against the control that recorded the lowest value. Also, CBTA improves soil pH (94%) and OC (87%) over the control as well as increases minerals such as N, P, K Ca, Mg, and Na at 19%, 37%, 19%, 53%, 43% and 36% respectively.  Organic fertilizer applications increase maize growth towards the later stage and were significantly different from the control according to DMRT at p<0.05. Cocoa bean testa ash (CBTA) and poultry dropping (PD) application registered over 47% increases of N levels in the soil, from 0.15% to 0.77% to 0.84%. Organic carbon increased as poultry droppings plus cocoa bean testa ash were added to the soil. Maize grain yield increased from control plot to 1.95 t ha^-1 in CBTA + PD plot. The study recommends an application rate of cocoa testa ash and poultry droppings for maize growth on this type of soil in this agro-ecology.

A research was conducted on the soils of teaching and research fadama farm of Kebbi State University of Science and Technology Aliero located at Jega, with the aim of assessing the soil quality irrigated with tube well water of the study area. The entire University Fadama land was divided into three sections namely T1, T2 and T3 and from each section, three (3) composite soil samples were collected. Each soil sample was collected 2meters away from a tubewell where water sample was also collected. Three (3) samples of the tube well water were collected from the three demarcated areas T1, T2 and T3, making a total of nine (9) samples. These samples were collected in a clean 75cl water bottle provided with a cap. Each water sample was analysed for pH, total dissolved solid (TDS), electrical conductivity (EC), sodium adsorption ratio (SAR), magnesium (Mg) and potassium (K). Soil sample was analyzed for pH, organic carbon, total nitrogen, available phosphorus. Result obtained showed that pH was 7.2, TDS 2.55 mg/l, EC 0.25 µs/cm, SAR 1.35, Mg 90.25, K 1.43 and RSC -3.8. Soil analysis showed that organic carbon content was 0.75 g/kg, total nitrogen 0.06 g/kg, Phosphorus 0.65 g/kg and CEC ranged 6.96-7.32 cmol(+)/kg. The study showed that soil in the area were low in fertility, therefore fertilizer of both organic and inorganic should be supplemented to make the soils more fertile. The soils were found to be free from salinity/sodicity problems at least for now.

Mitigation of climate change is one of the major environmental challenges facing the globe. In this context, homegarden agroforestry systems (HGAFs) have large potential for climate change mitigation. Therefore, this study was initiated to estimate the biomass and soil carbon stocks of HGAFs in relation to adjacent Natural Forest (NF). It also analyzed the relationship between woody species diversity, evenness and richness with biomass and soil carbon stocks. Three sites were purposely selected on the basis of the presence of HGAFs and NF adjacent to each other. Random sampling was used to select representative homegardens from the study population. In NF, a systematic sampling technique was employed. A total of 60 plots with a size of 10 m x 20 m were used to collect vegetation and soil data in both land uses. Soil samples were collected from each plot of the samples laid for vegetation sampling. Accordingly, 120 composite and 120 undisturbed soil samples from 0-30 cm and 30-60 cm soil depths were collected for soil organic carbon (SOC) and bulk density analysis respectively. Biomass estimation for each woody species was analyzed by using appropriate allometric equations. The result showed that the total amount of carbon stocks was 148.32±35.76 tons ha^-1 and 157.27±51.61 tons ha^-1 in HGAFs and adjacent NF respectively which did not vary significantly between the two studied land uses (P > 0.05). The finding also shows a positive but non-significant (P>0.05) relationship between carbon stocks and woody species diversity, richness, and evenness. Specifically, in NF lands, woody species diversity with SOC (r=0.36) and in HGAFs species richness with biomass carbon (r=0.39) was correlated positively and significantly (P=0.05). We concluded that HGAFs have the same potential as the NF for carbon stock accumulation and to counteract the loss of biomass.

The study was conducted from January to April 2018 to estimate ecosystem carbon stock and tree species diversity at National Botanical Garden, Bangladesh. Transects line method square plots with a size of 20 m × 20 m were used. So altogether there were total eighty-three sample plots in National Botanical Garden. Above ground carbon (AGC) and below ground carbon (BGC) biomass stock was 192.67 and 31.34, respectively and soil organic carbon mean value of 27.52 Mg ha^-1, 21.45 Mg ha^-1 and 16.23 Mg ha^-1, respectively for 0-10 cm depth, 10-20 cm and 20-30 cm depth. The average number of tree species per hectare was 128 with a mean value of each plot 3.00 to 9.00 species. The average number of trees in National Botanical Garden (233 tree ha^-1), basal area (21.45 m² ha^-1) and mean DBH (39.86 cm). Tree diversity range from 0.25 to 1.86 and the mean value of (0.93 ± 0.14) in National Botanical Garden. A relationship such as biomass carbon with the basal area, mean DBH, stem density and tree diversity were estimated. Among these, the relationship between basal area and biomass carbon showed positive significant correlation. Therefore, the results of the study confirmed that the selected botanical garden can serve as a valuable ecological tool in terms of carbon sequestration, diverse tree species and storage of soil organic carbon.