Agricultural Engineering
Year:2011 | Volume:33 | Issue:2|Papers Count:8

To evaluate the effect of two sugarcane harvesters (tire- and track-wheel) on soil compaction during the sugarcane harvesting at different soil water contents, soil bulk density and soil strength were measured. The field experiments, measurement and laboratory tests were carried out on Debal Khazaei agro industrial sugarcane fields in Ahvaz, Iran. The soil water contents were adjusted to low (0.09-0.14g/g), medium (0.14- 0.19g/g) and high (0.19-0.23g/g). The bulk density of soil profile at 0.10-0.15m layer increased from 1.6 g/cm³ for control plot to 1.7g/cm³ after tire-wheel harvester with 6.1% increment ratio in high soil water content. However, for chain-wheel harvester, the increment ratio in high soil water content was 3.9%. This result showed the benefit of using tire-wheel harvester in reducing soil compaction. The maximum increment ratio were 11.9% for tire-wheel harvester and 9.5% for chain-wheel harvester treatment after two trailer passes. While soil water content increased from low to medium, soil cone index raised, but this index decreased after medium soil water content to high soil water content. Almost, all trends in medium and high soil water content demonstrated significant increase in soil penetration resistance difference with harvesting operation. No significant increase in soil strength was observed at low soil water content after two harvester passes. After harvester passes, tractor transporter and trailer had two passes on soil. Finally, soil was compacted to a depth of at least 0.50 m with track-wheel harvester at medium soil water content. The maximum of soil strength increased for deep soil was 1.1 Mpa and accrued in 0.35m depth of soil when using track-wheel harvester, and so it raised cone index to 3.95 MPa. During sugarcane harvesting, track-wheel harvester had no excellence in reducing soil compaction compared with tire-wheel harvester. It is recommended, that harvesting at low soil water content with desirable drainage and control traffic has low damage on soil properties and re-growing of sugarcane for the next harvest.

This research was conducted to study the effects of tractor drive wheel tire size on slip which is an effective factor of traction efficiency. For evaluation of tires performance, slip of tractor MF 285 drive wheels was compared in two systems tillage operation including moldboard plowing on loamy soil having crop residues and disk harrowing on plowed soil. Tire dimensions were 18.4-30 and 13.6-38. Analysis of variance of the data indicated that tire size had significant effect on slippage and travel speed both in primary and secondary tillage operations. The maximum rates of slip were related to tire 13.6-38 in plowing and disk harrowing about 16.02% and 16.62%, respectively. Tire 18.4-30 in plowing operation had the minimum rate of about 9.18%. More slip of tire 13.6-38 caused tractor speed and consequently effective field capacity reduction in disk harrowing. Slip rate of tire 13.6-38 (narrow tire), was in the best range of slippage (10-20%). Thus using this size for tillage operation in loamy soils is preferable and there is no need to change tires for preserving operation of row-crop planting.

Application of proper technologies like conservation tillage systems as one of the well known methods in sustainable agriculture can cause the reduction of the soil loss process and increase sustainability. Considering the importance of the crop residue on the soil surface by employing conservation tillage, productivity is an effective means of increasing crop yield. Therefore, to study the effects of conservation tillage methods on soil physical characteristics, a factorial complete block design with three replications was applied in Dezfoul, Khouzestan province, Iran in 2007. One pass stalk shredder, two pass stalk shredder and one pass a disk for shredding crop residue was applied. Also combination tillage and a disk were the tillage machine treatments. Soil bulk density, cone index, soil moisture content and soil clod mean weight diameter were measured. Results showed that the highest soil moisture content was achieved in depths 0-5 and 5-10 cm with an average of %14.4 and %15.18 where the disk treatment was applied. The use of two pass stalk shredder followed by combination tillage reduced the soil clod mean weight diameter to 0.99 cm compared with one pass stalk shredder followed by a disk. The minimum soil cone index (0.67 MPa) was measured where the use of one pass stalk shredder followed by the combination tillage was practiced.

Potassium (K) trapped between interlayers of clay minerals is an important source of K for plants in many soils. The rhizosphere of plants, particularly the organic acids secreted from roots, can release K from micaceous minerals and also cause their transformation. The objective of this study was to investigate the intensity of micaceous minerals transformation in the rhizosphere of alfalfa. An experiment was carried out under the greenhouse conditions. Alfalfa was grown in pots that consisted of a mixture of quartz sand and biotite or muscovite or phlogopite for a period of 90 days. The plants were irrigated with distilled water and complete or K-free nutrient solutions. After 90 days, K uptake by plants was measured. Also, the clay size particles in each pot were analyzed using x-ray diffraction. Results showed that alfalfa was able to transform part of both biotite and phlogopite to vermiculite by releasing their potassium. Vermiculitization intensity, based on the comparison of 1.45 to 1.0 nm peak intensity ratio, indicated that the rate of transformation very much depends on the quantity of K uptake by plants. No X-ray detectable transformation of muscovite was recognized.

In this research, effects of moisture content and particle size on compaction force and hardness of alfalfa pellet were studied. The experiments were carried out on grinded alfalfa in two screen sizes 3.26 and 4.75 mm and three moisture levels of 10, 15 and 20%. The results showed that moisture, particle size, and their interaction have statistically significant effects (P<0.01) on compaction force and pellet hardness. The increase of moisture content and particle size led to increased compact force, and minimum force 2549.3 N was obtained in moisture content of 10% and particle size 3.26 mm. Pellet hardness decreased with increasing moisture content, and increased with increasing particle size. Maximum hardness (345.09 N) was obtained at moisture content 10% and particle size 4.75 mm. To predict pellet hardness based on moisture content and particle size, single and two variable regression equations were studied and a two variable regression model with R2=0.96 was obtained. Considering the hardness as the most important physical property of pellets, moisture content 10% and particle size 4.75 mm were recommended in which compaction force would be 2700N.

In order to investigate the effect of nickel (Ni) and cadmium (Cd) resulting from sewage sludge (SS) and municipal solid waste (MSW) contamination on the amount of microbial respiration and acid and alkaline phosphatase enzymes activity, a field experiment was conducted as randomized complete block design in split-plot arrangement with three replications in 2008. The main plot was SS and MSW at three levels (0, 20 and 40 ton/ha) and sub-plot, period of application (2006, 2006 and 2007, 2006-2008) was considered. The results showed that application of SS and MSW in the different treatments was significant on amount of heavy metals and biological factors. Application of 40 ha-1 ton sewage sludge, for three continuous years, increased the accumulation of Ni and Cd (total and available) in soil and decreased the acid and alkaline phosphates enzymes activity, but the accumulation of Ni and Cd did not have any negative impact on microbial respiration in all treatments. The total amount of Ni and Cd showed positive correlation (P<0.05) with the amount of microbial respiration and negative correlation (P<0.05) with acid and alkaline phosphates enzymes activity, respectively. Therefore, long-term application of SS and MSW, in addition to accumulation of heavy metals, can decrease enzyme activity and increase soil microbial respiration.

Salinity is an important environmental stress causing a negative impact on the soil biological activity. Application of organic and inorganic amendment in saline soil can modify the adverse salinity effects on microbial activity and biochemical characteristics of rhizosphere. The objective of this study was to investigate the effect of irrigation water salinity and organic and inorganic amendments on microbial respiration and soil acidic and alkaline phosphates activity in second node and full bloom stages of soybean. A factorial experiment consisting of five salinity levels (i.e. S1=0.8 S2=1.6 S3=3.2 S4=4.8 and S5=6.4 dS m-1 from the sea water source) and five amendment treatments including T1 (control without amendment), T2 (20 t ha-1 gypsum), T3 (20 t ha-1 manure), T4 (10 t ha-1 gypsum+10 t ha-1 manure), T5 (15 t ha-1 gypsum+15 t ha-1 manure) arranged as randomized blocks design with three replications was conducted under greenhouse conditions in 2009. Results indicated that irrigation water salinity reduced soil microbial respiration and acidic and alkaline phosphates activity in the second node (V2) and full bloom (R2) stages of soybean. But application of soil amendments (organic and inorganic) were increased biological indicators. In the second node stage (V2), application of organic amendments (T3) at all salinity levels had most microbial respiration and enzyme activity in comparison to control treatment. Microbial respiration, acid phosphates and alkaline phosphates were increased by 55, 24 and 27 percent respectively. Soil microbial respiration and enzyme activity of acid and alkaline phosphates in the full bloom stage (R2) decreased with salt accumulation by saline irrigation water application. Using mineral and organic amendments together (15 t ha-1 gypsum+15 t ha-1 manure) had the greatest effect on microbial respiration and enzyme activity in different salinity levels in the full bloom stage (R2).

Nitrogen use efficiency (NUE) enhancement is very important both for agricultural productivity and reducing environmental pollution. Thus, this research was conducted to investigate the best management of nitrogen fertilizer application from different sources on wheat yield (Chamran cultivar) at Shavour Research station in Khuzestan province - south west of Iran. A complete randomized block with five treatments was carried out in this experiment. Treatments include (T1) application of chemical fertilizer except for nitrogen based on soil test analysis as control plot, (T2) 150 kg N/ha from urea component divided in three times application at sowing time, stem elongation and beginning of flowering as farmer’s conventional treatment, (T3) 150 kg N/ha from urea, divided in two times, 50 percent at the beginning of stem elongation and 50 percent at the flowering stage, (T4) 150 kg N/ha divided in three times, at the sowing stage (one third of N with sulfur covering, SCU), stem elongation and the beginning of flowering (two third of N as supplementary fertilizer), (T5) 150 kg N/ha divided in three times, one third at the sowing stage from macro-fertilizer source and two third from urea source as supplementary fertilizer in two times. The results showed that application of different nitrogen fertilizers had significant effects (p<0.05) on biomass, grain yield, grain weight, tiller number, spike number, grain nitrogen percentage, harvest index, and NUE. However, T2 treatment resulted in highest yield of 5291 kg/ha, though in terms of NUE, T3 showed the highest rate of 10.1 kg grain/kg N compared to the other application of fertilizer treatments (p<0.05). The NUE increment rates of T3 compared to T2, T4, and T5 treatments were 6.38, 13.93, and 13.39 percent, respectively. There was no significant difference between treatments in terms of nitrogen apparent recovery fraction. Thus, it is concluded that the timing of N fertilizer application is a very important factor during wheat crop growth and the application of nitrogen fertilizers should be reduced during pre-sowing stages of wheat crops.