University of Khartoum

Impact of Layers of Organic Amendments on Cumulative Evaporation, Soil Moisture Redistribution and Conservation in Sandy Soil Columns

Impact of Layers of Organic Amendments on Cumulative Evaporation, Soil Moisture Redistribution and Conservation in Sandy Soil Columns

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Title: Impact of Layers of Organic Amendments on Cumulative Evaporation, Soil Moisture Redistribution and Conservation in Sandy Soil Columns
Author: Saeed, Mohamed Fathelrahman Mohamed
Abstract: A green house column experiment was undertaken to investigate the impact of layering soil mixed with organic amendments at two depths in a sandy soil on cumulative evaporation, soil moisture redistribution and conservation. The treatments consisted of a control and three organic amendments: chicken manure (CHM), dry sewage sludge (DS) and farm yard manure (FYM), each was layered at two depths: 0-5 cm and 25-30 cm and replicated three times. The statistical design was a randomized complete block design with three blocks and seven treatments randomly arranged in each block. A bulk surface (0-10 cm) non-saline non-sodic sand sample was collected from El-Rawakeeb soil, which was classified as mixed, koalinite, isohyperthermic, gypsicTypicCamborthid. The soil particle-size distribution was determined using the hydrometer method, pH was measured using a pH meter, EC was measured by a conductivity meter, Na+ by flame photometer and (Ca+Mg)++ by titration against EDTA. SAR was calculated by the following equation: SAR = [Na+]/ [(Ca+++Mg++)/2] Where, the ionic concentrations were expressed in me/l (mmol+/l). Twenty one 70-cm long columns were constructed from eight sections differing in length (20, 10, and 5 cm) of polyvinyl chloride tubes of diameter 10.5 cm and joined together with adhesive tape. The column was then closed at the bottom end by a piece of cloth firmly held with thin iron strings. The soil was uniformly packed in the bottom 60 cm and a top 10-cm section was left for adding irrigation water. The mean soil bulk was 1.55 g/cm3. The amendments were air dried, crushed, passed through 4-mm sieve and retained in a 3 mm-sieve. The latter fraction was used in the study. The rate of application of each amendment was equivalent to 20 ton/ha. Each amendment was mixed with enough soil to fill a 5-cm section, either as a surface layer (0 - 5 cm) or a sub-surface layer (25-30 cm) of the soil column. After placement according to the statistical design in the green house, each was then irrigated every week by adding 400 ml. The weight of each column was measured and the cumulative evaporation (Ec) was calculated daily weight difference from knowledge of the weight of empty column, column plus moist soil and column plus oven-dry soil. This process was continued for three months. By the end of the 12th week, each column was sectioned using a razor and the soil moisture content in each section was determined gravimetrically. The data provided the soil moisture distribution by the end of the experiment. From these data the soil moisture conserved in each column was also determined. For all treatments, Ec data during a week, a month or three months consistently showed highly significant (P  0.01) linear increase with increase of time with very high coefficients of determinations. Consistently, the control treatment gave the highest Ec. This is due to the high matric suction gradient between the evaporating bare soil surface and the moist subsurface and its relatively high hydraulic conductivity making the water more available for evaporation. Statistical analysis of the 3-month pooled data showed that the control treatment significantly (P  0.05) gave the highest mean Ec value which was 4.3 mm/day. The three organic amendments reduced Ec regardless of it layering depth. For the 3-months pooled data Ec was 3.1 mm/day for CHM25-30 and 2.7 mm/day for CHM0-5; 3.1 mm/day for DS25-30 and 2.7 mm/day for DS0-5; 2.8 mm/day for FYM25-30 and 2.6 mm/day forFYM0-5. The 3-month pooled data showed that CHM0-5, DS0-5 and FYM0-5 significantly (P  0.05) reduced Ec by 38.5%, 37.9% and 36.6%, respectively. CHM25-30, DS25-30 and FYM25-30 reduced Ec by 31.9%, 29.1% and 33.5%, respectively. The organic amendments significantly modified the soil moisture distribution in the soil columns. In general, the weighted-mean soil moisture content (WMC) in the top 30% of the soil column, was in the following significant order: CHM0-5> control = CHM25-30. Whereas in the top 50%, WMC was in the following significant (P  0.05) order: CHM25-30> CHM0-5> control. For both DS and FYM treatments, the trends of the weighted mean soil moisture content (WMC) in the top 30% or 50% of the column were similar to those of CHM treatments. The incorporation of organic amendments enhanced the amount of water conserved (AWC) in the soil columns. The AWC by CHM25-30, DS25-30 and FYM25-30 were 199%, 220% and 324% that of the control, respectively. The AWC by CHM0-5, DS0-5 and FYM0-5 were 164%, 171% and 154%, respectively. Restriction of upward movement of water by the sub-surface application of organic amendments was evidently more significant than inhibition of evaporation by surface incorporation of organic amendments
URI: http://khartoumspace.uofk.edu/123456789/24492


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