THE SCIENTIFIC JOURNAL OF AGRICULTURE (SJA)
Year:2003 | Volume:25 | Issue:2|Papers Count:15

Irrigated land in area such Iran, usually requires subsurface drainage for the removal of excess water and dissolved salts from the root zone. Calculation of drain spacing is based on theoretical relationships. In practice these theoretical equations fail at field conditions. This is due to some in herent assumptions which made during derivatign of the equations. Therefore theoretical relationships have to be tested and evaluated under field conditions. Results obtained from such evaluations and experiments lead to more reliable design of drainage system under similar soil and climatic condition. The purpose of this investigation was the selection of most suitable drainage spacing design formulas in the northeastern region of Ahvaz representing a relatively large agricultural development region. Necessary data like depth of irrigation water, water table fluctuation, soil hydraulic conductivity etc. were regularly collected for a 130 day period starting Jan 1, 2000, on a 50 ha experimental site belonging to Ramin Experimental site of Shahid Chamran University. The collected data were used to calculate drain spaces by solving unsteady state drainage equations. The resulted data were then campaired with actual data. The results showed that the Dumm Equation gives the best predication for 60m and 80m drain spacing in comparison to actual data.

In order to study the effects of soil compaction and phosphorus (P) fertilizer on yield and yield components of corn (Zea mays L.) an experiment which had a randomized complete block design with four replications was carried out. In this study, four levels of soil compaction including 0, 250,500 and 750 kPa and three levels of P fertilizer including 0, 250 and 500 kg ha-l super phosphate triple were used. P fertilizer was applied in a banding method with 10 cm deep from soil surface and 10 cm distance from sowing line. Soil compaction treatment was carried out with a John Dear tractor, model 3140 with pace of going and coming back among cultivated rows. The results of this study indicated that compacting the soil to a penetration resistance of 250, 500,750 and 900 kPa had a significant effect (p ? 0.01) on economical and biological yield and yield components of corn plant. However, P application and interaction between P and soil compaction had no significant effects on yield and yield components of corn. The highest economical and biological yields of corn observed in control treatment (no compaction) were 819 and 1496 g m-2, respectively. Economical and biological yields of corn decreased 28% and 23% respectively as the soil was compacted to a penetration resistance of 900 kPa. The greatest effect of soil compaction on yield components was on the number of seed per row (23% reduction) and the smallest effect of soil compaction was on seed weight (5% redqction). Increasing soil compaction decreased the rate of grain filling (37 % ), but increased the duration of grain filling (13% ), which the final weight of corn seeds was significantly affected by the rate of grain filling.

The Common lambsquarters(Chenopodium album) as well as most of the herbaceous weed species have allopathic effects on crops. A laboratory study was carried out to determine the effect of aqueous extract of biomass residues of Chnopodium album on early vigor of two wheat varieties. Weed was harvested at maturity and dried in shade. Seed lot of two wheat varieties (Flat and Atila ~ 4) was used in this study. These wheat varieties are commonly cultivated In Iran. Twenty five seeds of each cultivar were placed in a 9 cm plastic Petri dish on Watman paper where 5 ml of aqueous extract was applied on the top of it. The treatments were arranged in Factorial system and a Completely Randomized Design with four replications were used to compare them. Treatments included of two wheat varieties {flat and Atila - 4), three extract concentrations of Chenopodium album residues and control (10,20 and 30 percent) plus control with no extract and two seed depreciations (0 and 8% Calcium hypo chloride). The result- of bioassays indicated that aqueous extract of weed along with seed depreciation significantly reduced percentage of germination, length of radicle as well as the length of hypoctyls, shoot and root weignt.

Among crop plants, sugarcane needs a great amount of nitrogen during its growth period. An increase in the efficiency of nitrogen application not only decreases environmental pollutions, but it is also economical. A field experiment was conducted in Experimental Fields of Karoun Agricultural and Industrial Co. in order to study the effects of nitrogen and micronutrients application on nitrogen efficiency in sugarcane. The treatments were arranged in split plots and were compared in Completely Randomized Block Design with three replications in 1996-1997 . The amount of micronutrients (in 6 levels) and nitrogen (in 3 levels) was used as main and sub plots respectively. The results of this study showed that the application of micronutrients had no significant effect on plant growth. Increasing in the amount of nitrogen application led to the significant increase in relative nitrogen content and nitrogen uptake, although the efficiency of nitrogen use, nitrogen uptake and nitrogen utilization significantly decreased as the amount of nitrogen application was increased.

Soil quality assessment is necessary for identifying the effects of different management systems on agricultural and natural ecosystems. Despite the importance of such studies and the extensive research that has been carried out in the world, there are limited information available on the influence of different land uses on soil quality in Iran. A soil quality assessment was performed in the hummocky terrain of Semirum area which is mainly used as apple gardens, range and dryland farming. The objective of this study was to identify appropriate indices for reflecting the effects of different land uses on soil quality. Two parallel transects, each of them 200 meters long, and 20 meters away from each other, were selected. Soil samples were taken from the top 15 cm and a total of 90 samples were takan. Organic carbon, pH, saturated hydraulic conductivity, microbial respiration, carbonates and phosphatase activity of the soil samples were measured. Results revealed that the amount of organic carbon, saturated hydraulic conductivity, microbial respiration and phosphatase activity were highest in soils under apple trees and lowest in dryland results further and the values in rangeland between the other two land uses. The indicated that land management in apple gardens, has improved the soil quality, whereas the management practices in range and dryland areas have resulted in soil degradation. Also, this investigation showed the efficiency of soil quality studies for the evaluation of peresent conditions of soil in agricultural and natural ecosystems.

Histopathology of Karnal bunt infected wheat was investigated using light microscopy. Susceptible wheat plants were inoculated by Goates" and Injection methods. During the early stages of infection, in the plants inoculated by Goates" method, hyphae were present intercellularly in the distal to midportions, but not basal portions of the glume and lemma, and were absent in the ovary, funiculus and rachis. In the plants which were inoculated by injection method, during the early stages of infection, intercellular hyphae were present in all portions of glume, lemma, and rachis, but not observed in the ovay and funiculus. Hyphae were seen In funiculus at a later stage. In all observations, it appeared that hyphae from different parts of spike grew toward the basal parts of florets ana entered to ovary through funiculus. Ten days after inoculation, developing teliospores were observed in the pericarp of the caryopsis, and 13 days after inoculation, mature teliospores with thick exosporium wall were developed.

The effect of different levels of forward speed (4, 6 and 9 km/hr ) and shield position on the performance of rotary tiller was evaluated. The performance parameters were pulverization, inversion, travel reduction, evenness of soil surface and plowing evenness efficiency. The soil texture was clay with 14 - 16% moisture content. A randomized complete block design (RCBD) was used for statistical data analysis. Experimental means were compared by Dunncan"s multiple range test. Nine treatments representing different levels of speed and shield position were replicated three times. The results showed that the effect of forward speed on the total pulverization, inversion and plowing evenness efficiency was highly significant and its effects on travel reduction and evenness of soil surface were significant and non - signifcant, respectively. The effect of shield position on pulverization and inversion was highly significant and its effect on travel reduction and plowing evenness efficiency was significant. The results indicated that the interactive effect of the two factors on pulverization and inversion was significant and their effect on travel reduction and plowing evenness of soil surface was not significant.

Sediment accumulation is a major problem which sometimes leads to a complete failure of a drainage system. This problem is often encountered in noncohessive soils like silty and sandy soils. Soil particles stop flowing into the drain tube when a bridge is formed above" the perforations. Therefore a relation between drain perforation and grain size distribution of the surrounding soil can be established to predict the amount of sediment entering through a perforation before a bridge is formed. Experiments were carried out using glass beads and different soil materials in. a permeameter like apparatus. Results indicated that a circular perforation will allow a smaller amount of sediment accumulation before the bridge is formed. It was also found that corrected hydraulic radius of the perforation multiplied by a constant coefficient of perforation and D10 of the surrounding soil, was the best soil factor in this regard. Finally a relationship was derived for the prediction of drain line sedimentation using hydraulic radius of the perforation and D10 of the soil.

In order to study the effects of intercropping on Behbahan local onion ,Primavera and Texas Early Grano cultivars and also to determine the best plant density for Behbahan local onion and Primavera cultivar an experiment was conducted for one year (1999-2000) at Behbahan Agricultural Research Station. A randomizedcomplete block design with twenty five treatments and four replications was used. The replacement series technique through strip intercropping method was carried out to form the intercrops. The treatments of experiment were pure stands cultivation of Behbahan local onion, Primavera and Texas Early Grano cultivars, intercropping cultivation of Behbahan local onion with Primavera and Texas Early Grano cultivars.All treatments (except for pure stand cultivation of Texas Early Grano cultivar which was planted in one plant density: 200000 plants / ha) were planted in six plant densities from 200000 to 500000 plants/ha . Analysis of variance showed that in regard to yield differences among different plant densities of pure stand cultivation in Behbahan local onion and Primavera cultivar were significant at 1 % level. Computation of LER (Land Equivalent Ratio) and RVT (Relative Value Total) showed that intercropping of Behbahan local onion and Primavera cultivar with 500000 plants/ha (BD6)was greater than unity. Ther- efore the adventageousness of this treatment was confirmed. According to obtained results the optimum plant density for Behbahan local onion and Primavera cultivar were 333333 (407,5 x cm spacing) and 400000 (505 x cm spacing) plants/ha respectively. Among all treatments of intercropping system, BPD I with mea n yield of 66.8 tons/ha,yield adventageousness of 5% and economical adventageousness of 6% is recommended. The effect of intercropping on bulb dry matter percent was not significant