 หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Green Structure for Soil and Water Conservation on Cultivated Steep Land) ผู้เขียน: Effiom Oku, Ambrose Aiyelari, Paul Truong สื่อสิ่งพิมพ์:pdf AbstractA study was conducted on a farmer’s field on a 35 % slope in the humid forest zone, Nigeria on the use of a green structure that performed some engineering functions on cultivated steep lands to help curtail soil and water losses. Treatments consisted of a vetiver grass strip as a green buffer structure at different surface spacings of 5, 15, 25 m with no vetiver as the control and were laid out in a randomized complete block design with three blocks. Twelve erosion plots each measuring 50 m long and 3 m wide were used for the study. The plots were planted with cassava and maize in a simple crop mixture. The runoff, soil loss and crop yield were assessed under the four treatments. The rainfall lost as runoff with no vetiver (control plot) was 24.8 % compared to 7.7, 11.5 and 11.6% lost on the green structure plots at spacings of 5, 15 and 25 m, respectively. Soil loss on the no vetiver plot was 40 times higher than the acceptable soil loss limit of 12 t.ha-1 yr-1 for the tropics, whereas the soil loss on plots under vetiver at spacings of 5, 15 and 25 m was 1.4, 6.8 and 6.5 times higher than the acceptable limit. The maize grain yield and the fresh cassava tuber yield were significantly lower in the control plots and highest with the 5 m spacing. A vetiver strip as a green structure was more effective at a spacing of 5 m as it reduced soil and water losses and increased crop yield. This spacing was also adequate for traditional pre- and post-farming activities. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Predictability of Philip and Kostiakov Infiltration Models under Inceptisols in the Humid Forest Zone, Nigeria) ผู้เขียน:Effiom Oku, Ambrose Aiyelari สื่อสิ่งพิมพ์:pdf AbstractKnowledge of the infiltration of water into a soil is very important for efficient soil and water management and conservation, especially when the water supply is through rainfall. For efficient irrigation water management, once field infiltration values are constant and the curve established for a particular soil, it is possible to determine during irrigation how long it will take to infiltrate a certain amount of water. Ring infiltrometer measurements were carried out at 10 m intervals down a 5% Inceptisol toposequence of 100 m length in a humid forest in southern Nigeria. The aim was to determine the infiltration capacity of the soil with slope positions and to fit the infiltration data into the Philip and Kostiakov infiltration models in order to quantify the hydrological behavior of the soil and the ability of these models to predict infiltration into the Inceptisols of a humid forest. The nonlinear least square procedure was employed to determine the parameters of the models—namely, the transmissivity and sorptivity of Philip’s model and the initial infiltration and the index of soil sorptivity reflecting the rate of declining infiltration capacity of Kostiakov’s model. The results indicated that the initial infiltration and cumulative infiltration ranged from 2.0 to 7.50 cm min-1 and from 84.90 to 555.20 cm after 6 h of elapsed time, respectively. The coefficient of determination was near unity indicating the models were a good fit for data and could be used to predict infiltration for the studied soil. Transmissivity values ranged from 0.14 to 1.29, putting the soil conductivity class between ‘very slow’ and ‘slow’. Sorptivity was very high with values in the range 1.20 to 8.08. The index of sorptivity of soil ranged from 0.65 to 0.88 indicating fairly high soil sorptivity and the initial infiltration of Kostiakov’s model ranged from 0.03 to 1.09. Goodness of fit was used to compare the measured and predicted infiltration values and showed that 10% and 50% disparities existed for initial infiltration and 30% and 70% disparities for cumulative infiltration under Philip’s and Kostiakov’s models, respectively. It can be deduced that Philip’ s model was more suitable than Kostiakov’s model for predicting water infiltration in Inceptisols of the humid forest zone of Nigeria. |
หัวเรื่อง:ไม่มีชื่อไทย (ชื่ออังกฤษ : Vetiver Seedlings Multiplication in Rice Husk Amended Soil and Crops Performance on Erosion-Prone Hillside under Vetiver Buffer Strips) ผู้เขียน:Effi om Oku, Ambrose Aiyelari, Olajire Fagbola, Ayuk Essoka สื่อสิ่งพิมพ์:pdf AbstractVetiver buffer strips hold back soil on cultivated hillsides. A major constraint in their adoption is the low availability of seedlings for the establishment of buffer strips. Two experiments were conducted. In the fi rst, vetiver grass strip spacing (VGSS) at 5, 15, 25 m and farmers’ practice (FP) (no soil conservation measures used) were established as treatments on erosion plots sited on a cultivated hillside with a view to identifying the VGSS that would best increase crop yields. In the second experiment, 0, 25, 33.33, 41.67 and 50 t.ha-1 of rice husk were applied as soil organic nutrient enhancer to identify the rice husk rate that would maximize vetiver seedling multiplication on degraded soil. A traditional crop mixture of maize and cassava was introduced on mounds. Maize grain yield was signifi cantly infl uenced by VGSS and FP. Maize yields were 18.7, 8.7 and 11.6% higher on VGSS at 5, 15 and 25 m, respectively than on the FP plot. Maize dry matter accumulation between the VGSS and FP plots were signifi cantly different. Fresh cassava tuber yields were signifi cantly infl uenced by VGSS. Fresh cassava tuber yields were; 36.6, 12.2 and 13.2% higher on the VGSS at 5, 15, and 25 m, respectively, than on FP. The signifi cant benefi cial effect of VGSS in increasing crop yields on the cultivated hillside was evident. The farmer’s fi eld soil used for the vetiver multiplication was degraded having a sand fraction of 886 g.kg-1 of soil and a clay fraction of 40 g.kg-1. The soil was naturally very low in calcium and effective cation exchange capacity, low in organic carbon, nitrogen, magnesium and sodium and medium in potassium. Plant nutrient analysis of the rice husk used in amending the soil showed that it was high in available phosphorus and potassium, and medium in organic carbon and nitrogen. Vetiver tillers increased with the application rate of rice husk. A rice husk rate at 33.33 t.ha-1 could be the optimum rate of application as there was no signifi cant tiller increase beyond this rate. |