Six runoff plots are constructed at MARDI Agrotechnology Park, Cameron Highlands measuring 2.5 by 10.0 m to measure runoff and sediment from a 5% slope. To each plot was fixed a small 3 L tipping bucket, constructed using an acrylic sheet inserted into an acrylic box. The bucket was connected to a plastic stilling basin before attaching it to the runoff plot. The size of the tipping bucket was determined based on the desired area of the plot, maximum rainfall intensity and expected runoff and also the diameter of the runoff water conveyor pipe which in turn will depend on the head of water. The bucket constructed could accommodate a maximum flow of 19.5 L/min in the area with a tipping interval of 9.2 sec per cycle.
Keywords: Runoff plots, tipping bucket, sediment, erosion
Nitrification inhibition of soil-N and applied fertilizer N is desirable as the accumulation of nitrates in soils in excess of plant needs, leads to enhanced N losses and reduced fertilizer N-use efficiency. The effect of twenty-two different organic carboxylic acids, representing aliphatic (C1 to C18), di-, chloroacetic, hippuric, benzoic and heterocyclic (furoic, nicotinic and isonicotinic), on nitrification in a semi-arid subtropical sandy loam (Typic Ustrochrepts) soil in a laboratory incubation experiment is reported. The compounds were screened at 10% of applied-N dose and incubated for a period of 21 days at 300°C, maintaining 50% of the water holding capacity of the soil. Most of the test acids were found to be mild inhibitors of nitrification. Nitrification inhibition was the maximum (31.4%) in nicotinic acid treated soil followed by isonicotinic, furoic, palmitic, and stearic acid treated soils (26.6-27.8%). Based on four indicators of inhibitor effectiveness, namely, concentration of ammonium-N and nitrate-N, and total mineral N, nicotinic acid showed the highest relative efficiency among all the test acids. A quantitative structure activity relationship (QSAR) model based on nitrification inhibitory activity [Arc sine (% NI)] and various physico-chemical substituent parameters for hydrophobic and steric properties has been developed using multiple linear regression (MLR) analysis technique.
Keywords: Nitrification inhibitors, organic carboxylic acids, urea, nitrification, nitrogen mineralization, QSAR
The main objective of this study was to develop and test a 3-D solar radiation model for maize (Zea mays L.). the model was developed by dividing the canopy space of maize into a network of 3-D cuboids, and for each cuboid, three properties were determined: 1) leaf area, 2) leaf orientation, and 3) mean traveling distance of a solar beam. These three properties were determined using the polygon clipping and ray-tracing algorithm. Then Beer’s law was used to determine the solar irradiance for the given cuboid. A maize field experiment (18 × 18 m, planting density of 6 plants m-2) was also conducted to test the model's accuracy. The canopy architecture of 3-6 maize plants was measured weekly starting 27 days from sowing. Solar irradiance was also measured diurnally. The model was shown to be accurate (mean error of 6%) when applied to all growing stages of maize, with no overall tendency to either over or underestimate the fraction of captured solar radiation. The simulated 3-D plant radiation regime showed that the diurnal changes in the spatial plant-radiation profile for sparse canopies (leaf area index of 0.9) was more varied than that for almost closed canopies (leaf area index of 2) which was more uniform and less diverse.
Keywords: Solar radiation, maize, canopy architecture, light interception, model
A field experiment was conducted to assess the effectiveness of fruiting positions along sympodia under varying levels and sources of potassium fertilizer on field grown cotton under an arid environment. Treatments consisted of four rates of potassium (0, 62.5, 125.0, 250.0 kg K ha-1) and two sources of potassium (K2SO4 and KCl). Cotton cultivar NIAB-Karishma (Gossypium hirsutum L.) was used as test crop. Plant mapping data showed that total nmber of fruiting positions, number of intact fruit on sympodia/monopodial and percent of bolls per position on sympodia differed greatly due to different doses of potassium fertilizer. The percentage of fruit retention was markedly improved due to increasing doses of K-fertilizer compared to K-unfertilized treatment. The percentage survival of harvestable bolls for the five first positions along sympodia at the end of season was 29, 26, 18, 13 and 8, respectively. Potassium fertilization stimulated cotton crop in lengthening sympodial branches and retaining more fruit on the three first positions and also at the bottom of the plant during the early reproductive phase. The fruiting pattern was 2 to 3 and 6 to 7 days vertical and horizontal fruiting intervals, respectively.
Keywords: Plant mapping, cotton, flowering intervals, sulphate of potash, muriate of potash
The degradation of paddy soils due to both physical and chemical processes. A study was conducted in Kelantan, Malaysia where the top and subsoils of two soil series (Tok Yong and Kg. Cempaka) planted with paddy and fruit trees were statistically compared. In this study, a field experiment was established to measure nutrient and sediment inputs/outputs in the paddy plots. The Tok Yong series under paddy and orchards differs significantly in its clay, pH and P values. In both the soil series, paddy cultivation has resulted in the depletion of clay and lowering of pH in the topsoils. The net sediment loss under paddy was about 3 to 4 t/ha/season. Sediment removal by surface water was the highest during the second rotovation and lowering markedly 90 minutes thereafter. There was an increase of K and Cu, but N and Zn decreased. Soil degradation was not easily visible in this study as its effects were compounded by the various yield improvement measures undertaken. Using farmer’s practices and subsidized fertilizer, the rice yield was about 3.5 t/ha, and this was increased to 6.5 t/ha when MARDI’s technology was applied. Using FERTO technology, which incorporates organic manure, the yield was further increased to 8.1 t/ha.
Keywords: Soil degradation, paddy soil, clay removal, nutrient loss
In this study, fecal bacterial adsorption in three different soils (clay loam, silt loam, sandy loam) was investigated. A wild strain of Escherichia coli (E. coli) isolated from animal wastewater was used in the study. For adsorption kinetics study, adhesion of bacterial cells to soil particles was found to be immediate. Percent adsorption was found to be dependent on the initial concentration of E. coli. Results indicate that at low E. coli concentrations (below 103 cfu/ml), the percent adsorption was very much less in sandy loam than in silt loam and clay loam. However, as the bacterial concentration increased, all the soils tested displayed higher bacteria adsorption with maximum values of 99.9% for clay loam, 99.9% for silt loam and 99.7% for sandy loam. Soil with higher clay content (35.2% and lower pH (pH 4.5)) had significantly higher capacity for adsorbing E. coli. Furthermore, E. coli concentration of 106 cfu/ml in suspension was found to decrease by 2 orders of magnitude in all the three soils. Therefore, land treatment of wastewater from animal farm lagoons should be considered to reduce microbial contamination of rivers.
Keywords: Adsorption, fecal coliforms, E. coli, soils, animal waste