y. raei

To evaluate the effects of wheat (Triticum aestivum) and oilseed rape (Brassica napus) strip intercropping on yield components, seed and biological yields of oilseed rape, field experiments were carried out as factorial based on randomized complete block design with three replications at Research Farm of Tabriz University, Tabriz, Iran during 2010-2012 cropping seasons. The first factor consisted of four types of wheat and oilseed rape cropping system, sole crop of oilseed rape (A1),: strip intercropping with 8:3 (A2), 12:4 (A3) and 16:5 (A4) of wheat and oilseed rape rows, respectively and the other factor consisted of two fertilizer levels, B1: 100% chemical fertilizers (urea and triple superphosphate) and B2: 50% chemical fertilizers biofertilizers (Nitrazhin and Barvar2). The results showed that strip intercropping of wheat- oilseed rape resulted in significant increase in yield components, seed yield per occupied unit area and biological yield per occupied unit area of oilseed rape as compared with mono-cropping. The number of silique per plant in intercropping systems was significantly higher than that of mono-cropping. The highest seed yield was obtained in the 16:5 rows of wheat-oilseed rape with 343.76 g.m-2 and the lowest mean was observed in mono-cropping of oilseed rape with 260.21 g.m-2. Biological yield per occupied unit area and seed yield per intercropped unit area in B1 were significantly greater than that of B2, but this treatment had no significant effect on the other traits. Because, B1 and B2 had no significant difference in seed yield per occupied unit area and due to the importance of reduction in chemical fertilizers consumption and food and environmental health care, strip intercropping of wheat-oilseed rape under 50% chemical fertilizers biofertilizers can be recommended as a suitable cultural method.

Management of soil fertility via biological fertilizers inoculation is one of the most important components based on sustainable agriculture. In order to investigate the effects of biological and chemical fertilizers on yield and some morphological traits of forage yield sorghum, a field experiment was conducted as factorial based on randomized complete block design with three replications at Agricultural Research Farm, Agricultural Faculty, Tabriz University during growing season of 2010-2011. The first factor consisted of chemical fertilizer levels of 210 kg.ha-1 urea (100%), 150 kg.ha-1 super phosphate triple (100%), urea (100%)+ super phosphate triple (S.P.T, 100%), urea 50%+ S.P.T. 50%, and control and the second factor comprised biofertilizer levels of biosuper, phosphate Barvar Π, biosuper+ phosphate Barvar Π and control. The result showed that the sorghum could be produced three harvests during a growth season under Tabriz climatic conditions. Dry forage yield, leaf dry weight and stem dry weight of sorghum in the second harvest were more than other harvests, but the leaf stem ratio at the third harvest was higher than others. At the first harvest, combination of super phosphate triple (100%)+ biosuper+ phosphate Barvar Π, at the second harvest, the urea (100%)+ super phosphate triple (100%)+ phosphate Barvar Π, and at the third harvest 50% urea+ 50% super phosphate triple+ biosuper+ phosphate Barvar Π, increased forage yield, up to 244.6 %, 344.3 % and 121.5 % compared to the control, respectively. Therefore, it was concluded that the sorghum forage yield was increased significantly with integrated application of chemical and bio fertilizers at three harvests compared to chemical and bio fertilizers usage, separately.

In order to study yield component and determinate the contribution of stem reserves to corn yield under effect of different densities and interference periods of sorghum, a factorial experiment based on randomized complete block design with three replications was conducted in 2002 on the Research Farm of the Faculty of Agriculture Tabriz University. Experimental factors were sorghum interference at different periods (0,14,28,42 days after corn emergence and also during plant life corn) with three densities (4,8,12 plants m-2). Characteristics of study were yield, yield component and the contribution of stem reserves to corn grain yield. The results showed that with increasing sorghum density and interference, corn yield components (except the number of grain rows) were decreased, due to shading and competition between plants for using available resources. Maximum grain yield and grain number per ear was obtained at pure corn plantation. With increasing sorghum density and interference periods grain yield decreased, and maximum corn yield loss was 38%, which occurred at the highest sorghum density and interference. Dry matter remobilization and contribution of stem reserves were significantly influenced by sorghum densities and interferences in corn grain yield. The highest contribution of dry matter remobilization and stem reserves to corn yield was obtained at maximum density and complete interference of sorghum. The least contribution of reserves was shown in pure corn plantation. This might be related to shading and competition between plants for light and other resources.

Concerning the effects of increasing the species number on the maintenance of ecological stability and agricultural ecosystems sustainability, two field studies were conducted in 2002 and 2003 to evaluate the effects of plant population densities on soybean and sorghum intercropping at the Research Center, the Faculty of Agriculture, Tabriz University, Tabriz, Iran. Cultural pattern was an additive series. The factorial set of treatments was arranged within a randomized complete block design with three replications. The first factor comprised soybean densities of 20, 30, 40, and 50 plants/m2, and the second factor consisted of sorghum densities of 0, 4, 8, and 12 plants/m2. The results indicated that both soybean and sorghum yields were significantly affected by soybean and sorghum densities. Soybean yield increased as density increased up to 40 plants/m2, and then decreased with increasing soybean density from 40 to 50 plants/m2. With increasing soybean density, sorghum yield was decreased. Sorghum and soybean yields, respectively, increased and decreased as sorghum density increased. On the other hand, Soybean and sorghum densities of 20:4 (1.6) and 50:12 (0.8) had the highest and the lowest LER (Land Equivalent Ratio), respectively. It was, therefore, concluded that intercropping of Soybean and sorghum, is more advantageous, compared to their pure cultivation in the same conditions.

A factorial experiment, based on RCB design, with three replications was conducted to evaluate the effects of rhizobial inoculation, urea, and weeds on soybean performance in the field. The factors under study consisted of inoculation and non-inoculation, three levels of 0, 150, and 300 kg/ha urea, and weed-control and weed-infestation. Results showed that weed-control, inoculation and urea application increased biological and seed yield. The highest effect on yield was due to weed control, followed by inoculation and urea application. Inoculation, weed-control and urea application of 300 kg/ha enhanced protein percentage in soybean grains. In this case, inoculation had the highest effect on protein percentage, followed by urea application and weed control. In contrast, only weed-control significantly increased seed oil percentage. Seed filling rate increased as a result of inoculation, but, seed filling duration was not affected by inoculation. Weed-control improved seed filling rate and duration. Urea application induced seed filling duration, but had not any effect on seed filling rate.