نشریه بوم شناسی گیاهان زراعی
سال چهاردهم شماره 3 (پیاپی 53، پاییز 1397)

The present research was carried out for determining spatial distribution type and developing sequential sampling models for precise estimating of corn leaf aphid, Rhopalosiphum maidis (Fitch) population in broomcorn, sorghum vulgare var. technicum, fields of Miyaneh region, Iran. To investigate spatial distribution pattern, population was sampled every 3 days on 50 broomcorn tillers to calculate variance and mean number of aphids at each sampling date. Taylor’s power law was more suitable and so its parameters was used to develop sequential sampling models using Green (1970) method at precision levels of D = 0.1 and D = 0.25. Results revealed high number of corn leaf aphid in broomcorn field with an aggregated dispersion pattern. Mean aphid population at different sampling dates varied from 5.22 to 109.10 aphids per stem. Estimates of spatial distribution parameters were used to develop sequential sampling models and sampling stop lines using Green (1970) method at precision levels of D = 0.1 and D = 0.25. Comparison of sampling models showed that sample size required for estimating aphid density significantly increased by decreasing precision level from 0.25 to 0.1. So, sequential sampling model at 0.10 precision level was time - consuming and it was not suitable for estimating corn leaf aphid population. However, sequential sampling model at 0.25 precision level reduced sample size required for monitoring R. maidis population in comparison to the fixed sample size method. In conclusion, sequential sampling model at 0.25 precision level could reduce sampling time and so, it recommended for estimating population in IPM programs of the pest in broomcorn fields of Miyaneh region.

To investigate the effect of different amounts of Hungarian vetch residues on growth and yield of wheat cultivars in cold regions, an experiment was conducted in a strip plot design based on randomized complete block design with three replications during the growing years of 2014-2017 at Dryland Research Institute of Iran, Maragheh Station. The amounts of vetch residues in three levels of 0, 1.5 and 3 ton/ha as horizontal factor and wheat cultivars including Homa, Azar2 and Baran as vertical factor were evaluated. The experiment was carried out on forage – wheat rotation farm, and the plant residues of the vetch were added to the experimental plots spread uniformly on the surface of the soil. Plant residues of 1.5 tons per hectare had a positive effect on early establishment of seedlings in the field, yield and yield components of wheat. Homa cultivar had the highest positive reaction to the addition of green vetch residues in the amount of 1.5 tons per hectare in terms of thousand kernel weight, grain yield, biomass yield, harvest index, productivity rate and recipitation efficiency index. Therefore, the maintenance of vetch residues of 1.5 tons per hectare can improve the yield of wheat.

To investigate the reaction of maize under drought stress to the application of manure, an experiment was conducted as split split plot based on randomized complete block design in Iranshahr, Iran. Drought stress included irrigation cut-off in two flowering and seed filling stages. Maize genotypes consisted of SC704, SC540, and SC647, and Maxima cv. and sheep and poultry were applied with the amounts of 10 and 5 t/ha. Plant height, number of seeds per row, ear diameter, 1000 grain weight, and seed yield were measured at physiological harvesting time. Tolerance indices including Stress Susceptibility Index (SSI), Tolerance Index (TOL), Stress Tolerance Index (STI) , Geometric mean productivity (GMP), , and Mean Productivity Index (MPI) were measured . Irrigation cuttings had a meaningful declining effect on all studied traits in all four cultivars especially in flowering stage. SC704 hybrid showed the highest drought tolerance to Iranshahr weather conditions.Compared to sheep manure, application of poultry manure increased yield and yield components of maize cultivar 704 in drought stress in flowering stage. SSI, STI, STI, GMP, TOL, and MPI introduced the SC704 maize hybrid as stress tolerance indices.Therefore, the use of poultry manure is recommended to achieve optimal yield in maize SC704 under drought stress conditions.

Foliar spraying of medicinal plants is one of the main techniques to improve their vegetative and reproductive growth. To evaluate the effect of foliage spraying of coneflower using chitosan and ascorbic acid on vegetative and reproductive traits, an experiment was carried out based on complete block design in three replications in filed condition located at Khalil Abad village in Ardebil province. Experimental treatments were foliage spraying of 0.1, 0.2, and 0.3 g/L of chitosan and ascorbic acid. The first spraying was on 8 July 2018 and repeated twice in one week intervals. Plants were harvested a week after the last spraying and in full flowering stage. The vegetative and physiological traits such as plant height, the longest stem length, leaf, lateral branches and flower number, leaf length and width, stem and capitol diameter, leaf, stem, flower and whole plant dry and fresh weight, and chlorophylle content were measured. No negative effect has been observed resulted from foliar spraying by these natural products. Spraying by chitosan in low concentration improved coneflower morphological traits. Ascorbic acid was only effective on leaf fresh and dry weight and root dry weight. Therefore, spraying with 0.1 g/L of chitosan would be recommendable for coneflower growth improvement in filed conditions.

To study the effect of herbicides on weeds control and yield and yield components of three corn cultivars, an experiment was conducted in split plot experiment based on randomized complete block design with four replications. The herbicides included Eradican, Eradican + 2,4-D, and Laso + 2,4-D assigned in main plots and maize cultivars included SC604, SC700, and SC647 SC were placed in in subplots. The effect of herbicide on dry weight of weed characteristics was significant. The lowest weed dry weight per square meter was obtained from the treatment of Laso + 2,4-D. In comparison to other herbicide, this herbicide also had more efficiency in weeds control. Grain yield, ear length and ear diameter were also influenced by herbicide. The effect of cultivar on 1000-grain weight was meaningful and SC647 had higher production capacity compared to other cultivars. The highest yield of corn was obtained from combination treatment of post-emergence of Laso and 2,4-D. Therefore, it is recommended to use this treatment because of the effective control of weeds, especially in the early period of corn growth, which has little competitive ability.

Environmental factors including temperature and anticipation have critical impact on vegetative and reproductive growth as well as secondary metabolites and quantity and quality of essential oils in medicinal plants. In this study, phytochemical characteristics of German chamomilelandraces collected fromthree watershed areas of Kaleibarchai, Hajilarchai, and Mardanagim of Arasbaran, Iran was surveyed using plotting method. Foliar essential oils were extracted by hydro-distillation using Clevenger apparatus and their yield and compositions were determined using gas chromatography and gas chromatography mass spectrometer methods. On the whole, 22 components were identified in German chamomile essential oils with α-bisabolol, Camazulene, α-phellandrene, E- β-Franesol, Z-E- Feranesol, and α-bisabolol oxide as the most important identified components. High temperature and anticipation caused increasing of α-phellandrene, α-bisabolol oxide Z-E- Feranesol in Kaleibarchai region. Also, low anticipation in Hajilarchai increased Camazulene and E- β-Franesol. On the other hand, low temperature in Mardanagim increased Camazulene and α-bisabolol oxide in collected samples. Therefore, collection of German chamomile from Mardanagim for high amounts active medicinal ingredients is recommended.