فصلنامه تحقیقات غلات
سال سوم شماره 2 (تابستان 1392)

Determination of evapotranspiration is necessary in water studies specially to estimate crop water requirement and to design irrigation systems. One of the most important stages in estimating crop water requirement is determination of crop coefficient (Kc) and reference evapotranspiration (ETo) as for factors such as growing period, crop species and cultivar. This experiment was conducted to derivate Kc for three rice varieties, Hashemi as a local cultivar, Khazar as an improved cultivar and Bahar as a Hybrid cultivar, in paddy fields of Rice Research Institute of Iran in 2009 and 2010. The values of crop evapotranspiration (ETc) were measured with installing three cylindrical mini-lysimeter for each cultivar. Derivation of Kc were done based on five ETo estimation methods including FAO Penman-Monteith, Radiation, Blaney-Criddle, Pan Evaporation and Hargreaves. As a result, water requirements for Khazar (526 mm) and Bahar (490 mm) varieties were 14.6 and 6.8 percent higher than Hashemi (459 mm) cultivar, respectively. The crop coefficients were varied between 0.76 to 1.09 for initial stage, 1.15 to 1.48 for mid-season and 0.91 to 1.21 for late-season based on ETo estimation method and rice cultivar. Difference between the gained Kc in this study with the recommended values by FAO shows that derivation of crop coefficient based on local conditions is necessary. The obtained Kc based on different ETo methods can increase estimation accuracy of water requirement in availability limitation to meteorological data. The results of this study can be used by local project managers, consultants and irrigation engineers in designing water projects and scheduling of water delivery in irrigation and drainage networks.

To study and comparison of different crop rotations based on wheat in regard to yield, economic performance, soil fertility, weed populations, pests and diseases, an experiment was conducted at Agricultural Research Station of Gonbad Kavous during five years (from 2005 to 2010 cropping seasons). The six crop rotation systems consisted of 1. wheat-wheat, 2. wheat-rapeseed, 3. wheat-chickpea, 4. wheatcotton, 5. wheat-watermelon and 6. wheat-sunflower, were evaluated in a randomized complete block design with 3 replications each in 180 m2 plots size. Performed rotation systems were based on prevailing cultivation of the region (wheat cv. Darya). Wheat plants were cultivated in all plots at the start and end of the experiment. Results from analysis of variance revealed that effect of rotation was significant on wheat characteristics including plant height, number of fertile spike per m2, number of seeds per m2, 1000 grain weight, number of fertile spikelets per spike and grain yield. Results of means comparison of treatments showed that highest (5343 kg.ha-1) and lowest (3990 kg.ha-1) wheat grain yield obtained from wheatchickpea and wheat- sunflower rotations, respectively. Based on the results of this experiment, wheatchickpea rotation can be recommended for the studied region.

To evaluate performance of multivariate statistical methods in detection of the most important effective traits on grain yield of 20 promising bread wheat lines and for determination of the role of each trait on yield changes, an experiment was conducted based on randomize complete block design with 3 replications in 2011-2012. Results of principal components analysis showed that three first principal components explained 72 % of the total variance. Accordion to the results, spike harvest index, ELWR and harvest index had highest effects on two first principal components. Cluster analysis by Ward’s method grouped the lines in 4 clusters. Discrimination function analysis confirmed the fourgroups derived from cluster analysis. Stepwise regression analysis indicated that harvest index, biomass and RWC were the most important effective traits on economic yield and explained 94% of its total variance. Results of path analysis showed that harvest index and biomass had maximum positive direct and negative indirect effect on economic yield, respectively, which can be used for selection of wheat varieties under terminal moisture stress condition.

Water in arid and semiarid regions is a limitation factor and recognition of water use efficiency is an essential parameter in yield increment of the crop plants. An experiment with 100 wheat lines and varieties was conducted in square lattice design (10×10) to identify the effects of different physiological traits on water use efficiency of wheat under rainfed conditions. Leaf relative water content, rate of water lost, photosynthesis rate, intercellular CO2 concentration, transpiration rate, stomatal conductance and chlorophyll index were measured at flowering stage. In stepwise regression analysis of PWUE as dependent variable, photosynthesis rate, transpiration rate and intercellular CO2 concentration entered to model and explained 88% of the total variance of PWUE. Path analysis showed that photosynthesis rate had positive and transpiration rate and intercellular CO2 concentration had negative effects on this trait. According to our results, selection of plants with higher photosynthesis rate and transpiration rate and lower intercellular CO2 concentration is recommended to improve PWUE.

To investigate integrated application of chemical, manure and biological fertilizers on growth characteristics of forage corn (SC.704), a field experiment was conducted at Faculty of Agricultural Sciences, University of Guilan, in 2011. The experimental design was carried out as randomized complete block design with ten treatments and three replications. Treatments were included nochemical, biological and manure fertilizers as control, chemical fertilizer (150 kg.ha-1 N and 40 kg.ha 1 P), biofertilizer (Pseudomonas fluorescens+ Azospririllum brasilenes), manure (28 ton.ha 1), 50% chemical fertilizer + biofertilizer, 75% chemical fertilizer + biofertilizer, 50% manure +50% chemical fertilizer, 25% manure + 25% chemical fertilizer+ bioferilizer, 75% manure+ biofertilizer and 50% manure + biofertilizer. Results showed that 100% chemical fertilizer and 50% manure + 50% chemical fertilizer treatments were not significantly different in forage yield, dry matter yield, leaf dry matter, ear dry matter, crop growth rate and leaf area index. Dry matter yield in 100% chemical fertilizer and 50% manure fertilizer + chemical fertilizer treatments were 19253 and 1617 kg.ha-1, respectively. The results of forage quality showed that maximum of protein yield, ash, water soluble carbohydrates, fiber and acid detergent fiber was obtained from 100% chemical fertilizer, 75% chemical fertilizer + biofertilizer, 50% manure +50% chemical fertilizers and 50% chemical fertilizer + biofertilizer. Therefore, using integrated chemical fertilizer, biofertilizer and manure application without significant decline in yield quantity and quality, could be decreased consume chemical fertilizer and its impacts on environment.

To evaluate the effect of manure and Azotobacter application on yield and yield components of maize, an experiment was carried out in Ecological Research Station of Khorramabad in 2007. Four plant densities (75, 85, 95 and 105 thousand plants per ha) and manure at 80% and 100% (24 and 30 ton.ha-1) and two levels of Azotobacter chroococcum (inoculation and uninoculation), were arranged in a split split plot design based on randomized complete block design with three replications. Results showed that plant density had significant effect on biological yield, grain yield and number of ears per unit area. Increasing of plant density from 75000 to 105000 plants.ha-1 increased 42% of biological yield, 65% of grain yield and 42% of the number of ears per unit area. Totally, results from current research showed that under climate conditions of Khorramabad, the autumn crops are harvested in early summer next year. Therefore, corn plant can be considered in rotation cycle as the second culture. Also, the plant density of 95000 plant.ha-1 and application of 24 ton.ha-1 manure for supplying plant nutrition are suitable for corn as second culture. It seems that there is not the suitable conditions to show the beneficial effects of bacteria in rich soils of nutrients (manure application).