نشریه زراعت دیم ایران
سال یکم شماره 2 (پاییز و زمستان 1391)

Breeding medics species to drought and salinity tolerant can play an important role in herb production and pasture rehabilitation. With the aim of study of the performance of annual burr medics under drought and salinity stresses، a pot study was conducted with factorial arrangement of treatments in a randomized complete block design in Shiraz University. Sown seeds were two types (threshed and unthreshed)، salinity stress had four levels (0، 4، 8، and 12 dSm-1) and drought stress had three levels (irrigated up to 100، 75 and 50% of field capacity). All stress treatments altered morphological traits and proline content. Increasing drought and salinity severity significantly declined germination percentage، plant height، vegetative vigour، leaf number and tiller number، although، proline content was enhanced. The plants grown from threshed seeds were affected more than unthreshed one. Overall، the applied stresses decreased germination and growth; but increased proline content of medics. Results indicated that sowing of threshed seed could improve germination and growth، especially under drought and salinity conditions.

Nitrate and ammonium forms of nitrogen are being applied to improve plant growth and uptake of other nutrients. Given that the effect of application of different nitrate to ammonium ratios accompanied by other fertilizers (i. e. Fe، Mn and Zn) has not been studied on wheat growth as well as uptake of Fe، Mn and Zn، three glasshouse pot studies were conducted with factorial arrangement of treatments in a completely randomized design (CRD) with three replications in the calcareous soil. In each experiment، the interaction of different nitrate to ammonium ratios and the fertilizer (Fe، Mn and Zn) rates were studied separately. The treatments were five nitrate to ammonium ratios (00/100، 25/75، 50/50، 75/25 and 100/00)، three levels of Fe (0، 5 and 10 mg/kg soil)، three levels of Mn (0، 3 and 6 mg/kg soil)، and three levels of Zn (0، 1 and 2 mg/kg soil). The results indicated that all nitrate to ammonium ratios، except 00/100، significantly increased wheat shoot and root weights. Similarly، in the presence of nitrate، the uptake of Fe، Mn and Zn were increased significantly. The uptake of nutrients was increased by increasing of Zn، Mn and Fe fertilizer application at different ratio of nitrate to ammonium. In addition، application of both nitrate and ammonium compared to their single application could promote Zn، Mn and Fe uptake at different rates of these elements. At single application of ammonium، increasing of Zn، Mn and Fe application promoted root growth and Zn، Mn and Fe uptake. It can be concluded that the presence of nitrate could increase growth of wheat and Fe، Mn and Zn uptake; but single use of ammonium may decrease growth and uptake of other nutrients.

Abiotic Stresses is one of the most important threatening factors for the production of wheat in cold dryland regions. In order to study some agronomic traits and cold tolerance in rain fed wheat، 20 advanced bread wheat genotypes were evaluated in Azna (regarding agronomic characteristics) and Maragheh for freezing test (LT50) Experimental Stations in 2005-06 cropping seasons. The experimental design was randomized complete block design (RCBD) with three replications. Analysis of variance showed significant difference among the genotypes in most of the traits in Azna region. Freezing test (LT50) study showed that different resistant level of cold tolerant in different date of seedling stages in wheat genotypes and highest cold tolerance related to after hardiness''s with LT50 = -17oC. Based on results Lines with highest grain yield under Azna dryland condition had more cold tolerance. Grain yield showed positive and significant coefficient with spike weight، 1000 kernel weight، biological yield، harvest index and straw yield. The pathanalysisshowed that1000 kernel weight (r= 0. 52**) andharvest index (r= 0. 48**) had highest positive and direct effects on grain yield. Based on results 1000 kernel weight، seed number in spike and harvest index were positive important traits to select of high yield potential lines under drought and cold conditions. Overall suitable genotype for cold and drought area such as Azna need to have more cold tolerance and adapted traits such as TKW، HI and seed per spike for high grain yield production.

Increasing crop competitiveness against weeds through crop management has been proposed as an agro-ecological approach. In this research، the effect of plant density on weed control، and determining proper seeding rate and row spacing was investigated. This experiment was conducted in a factorial strip-block in a randomized complete block design (RCBD) with four replications. The experiment was repeated in three cropping seasons (2007- 2010) under rainfed condition. Weed conditions with two levels (weedy and weed free) was considered as horizontal factor and plant density (40، 70، 100 and 130 plant m-2) and row spacing (15، 30، 45 and 60 cm) were combined as factorial treatments and considered as vertical factor. Results of combined ANOVA showed that the seed yield was significantly influenced by year، which showing diverse environmental conditions in the experiment. The weed and row spacing treatments had significant effects on grain yield، where weed-free treatment with 334 kg/ha، 15 cm row spacing with 349، and 30 cm row spacing with 329 kg ha-1 had the best yield production among the treatments. The results indicated that oil seed percentage in weed-free condition with mean value of 30. 9% was significantly higher than weedy condition with mean value of 29. 2%. Interaction between weed condition and row spacing was significant and the highest oil percentage was achieved in 30 and 45 cm row spacing under weed-free condition. Mean comparison for oil percentage based on plant density showed that the treatments of 40 and 70 plant m-2 had significantly higher oil percentage than the treatments of 100 and 130 plant m-2. It can be concluded that less row spacing (15 cm) and medium seed rate (70 plant m-2) can be recommended for higher seed yield and oil production in safflower.

To study the effect of sowing date and supplemental irrigation on grain yield and distribution and remobilization of phosphorus in canola (Brassica napus)، this experiment was carried out in 2 years (2005-07) in research station of Gonbad. The study was carried out in two types of irrigation treatments (rainfed، supplemental). Both experiments were carried out in randomized complete block design (RCBD) arranged in split-plot. The main plot factor was five sowing dates (6 Nov.، 6 Dec.، 4 Jan.، 5 Feb.، 5 Mar.) and sub-plot factor was two cultivars (Hyola401 and RGS003). Late sowing date increased shoot P concentration. At the beginning of grain filling، P concentration of stem، leaf and pod ranged from 0. 12 - 0. 22%، 0. 26 - 0. 44%، and 0. 49 - 0. 80%، respectively. At maturity، P concentration of stem with pod-sheet، leaf and grain ranged from 0. 04 - 0. 10%، 0. 16 - 0. 24%، and 0. 56 - 0. 74%، respectively، across years and irrigation conditions. At maturity، mean grain P of Hyola401 and RGS003 cultivars were 17. 2 and 13. 8 kg/ha in irrigated; and 13. 5 and 11. 0 kg/ha at rainfed condition. The existence of positive correlation between grain yield and shoot P remobilization rate shows the importance of shoots P in higher yield. The contribution of stem and leaf P remobilization on seed yield was strong and negative، explaining 90 and 85% of the variation for Hyola401 and 93 and 91% of that for RGS003، respectively; indicating the increase of P remobilization contribution in seed yield under stress conditions. Early sowing date could accelerate plant growth and phenological stages، hence، plant can escape from terminal heat stress. This led to increase in seed yield.

In order to study the effect of folic acid on seed reserves partitioning and early vigor of seedlings of Kavir wheat cultivar، an experiment was conducted in a completely randomized design with 0، 12. 5، 25، 50، 100 and 200 mM of folic acid. Results of this study indicated that dry weight of seeds decreased in a same pattern in all treatments and about 6-8% of total seed was structural section. Variation in the seedling dry weight in control and folic acid treatments was similar but decreasing of seedling dry weight in control and folic acid treatments continued 10. 46 and 7. 93-8. 53 days after soaking، respectively. Then، dry weight of seedlings were increased because of reaching to autotrophic stage. It is worth mentioning that acid folic could shorten the time required to reach the onset of autotrophic stage (beginning of seedling dry weight increase) and the complete autotrophic stage (time of seedling dry weight to reach the initial weight of seed). Seedling، shoot and root dry weight changing trends were similar in all treatments. However، folic acid application increased the rate of dry weight accumulation in each of the aforementioned plant parts. Also، decrease of seed dry weight was similar between control and folic acid treatments، but folic acid application increased the rate of seed reserves consumption in comparison with control. Results showed that seed reserves conversion efficiency to seedling structure in studied treatments were variable in the range of 20-62. 96%. The minimum and maximum conversion efficiency belongs to 400 and 25 µM folic acid treatments. The differences between treatments could be due to partitioning manner of seed reserves to growth and/or maintenance respiration. Growth and maintenance respiration of the studied treatments were variable in the ranges of 12. 12-63. 26% and 36. 7-87. 9%. It can be concluded that folic acid application increases seedling vigor by increasing conversion efficiency and growth respiration of wheat seedling.

The Dragon''s head (Lallemantia iberica F. & C. M.) can be introduced as a new oilseed crop to cold rainfed areas because of its unique characteristics. The field trial was carried in a split-plot factorial in a randomized complete block design (RCBD) with three replications in Dryland Agricultural Research Institute (DARI) in 2010-11. The treatments included three landraces of Dragon’s head as main plots and two seeding rates and three sowing dates as sub plots. The effect of landrace، sowing date، seed density and their interactions were significant on some studied traits. Grain yield had positive correlation with seed germination (0. 72**)، harvest index (0. 39**)، dry biomass (0. 30*) and plant height (0. 30*) and number of seeds per plant (0. 56**). Based on path analysis، seed germination and plant height had the highest positive direct effect on grain yield; and accounted 75% of the yield variation. Kurdish-2 landrace at 400 seed m-2 density produced the highest grain yield of 1235 kg ha-1. It can be concluded that some Dragon’s head landraces (e. g، Kurdistan- 2) could be recommended as a new crops for autumn sowing in Maragheh and similar cold rainfed areas of the country.