مجله تولید گیاهان زراعی
سال سوم شماره 4 (زمستان 1389)

The seedbed preparation and cereal residue present due to limit of maize (Zea mays L.) growing period are a major challenge in double cropping after winter cereals in Iran as: Shahrekord. In this research, effects of various seedbed preparation methods and crop residuea managements on vegetative growth and yield of forage maize (KSC 704) were studied in a barley-maize double cropping during 2008 in the Agricultural Research Field, Shahrekord University. Three residue management treatments including standing, partly removed and burning along with five tillage systems (moldboard+disk; chisel+disk; moldboard; chisel and furrower as the reduced tillage) were laid out in a split-block design with three replications. The results showed that although burning treatment had maximum of leaf number, plant height, leaves weight, ear weight and forage yield, but there was no significant difference with partly removed residue treatment. Residue treatments had no significant effect on number of ear per plant, stem diameter, stem weight and forage yield. Although, moldboard+disk treatment had the highest leaf area index, leaves weight, ear weight and forage yield, but there was no significant difference with moldboard treatment for all measured characteristics except leaf area index. There was no significant interaction between residue management and tillage treatments for all the measured characteristics. The results of this research indicated that using of moldboard in the case of partly removed residue would be appropriate seedbed preparation method in a barley-maize double cropping.

In order to study the effect of uniconazole and cycocle growth regulators on growth, yield and nutrients content of pearl millet in drought stress condition, a field experiment was conducted in 2007-2008 in Agriculture Research Center of Zabol University. The experiment was conducted in split plot base on randomized completely block design with tree replications. Main plots were different levels of drought stress included: full irrigation, withholding irrigation in vegetative growth stage (beginning of rapid stem development), and withholding irrigation in flowering stage. Sub plots were of four levels micronutrients foliar application treatments (foliar application, foliar application of uniconazole, foliar application of cycocle, and foliar application of uniconazole + cycocle). In this experiment plant height, dry matter and grain yield, 1000-seeds weight, harvest index and absorption nutrients (N, P and K) content in forage were measured. The Results indicated that the highest plant height, dry matter and grain yield, 1000-seeds weight and harvest index obtained from S1 treatment. Furthermore the highest nitrogen and phosphorus content achieved from 0S1 treatment. But it hadn’t significant effect on potassium content in forage. Foliar treatments the highest plant height obtained from no foliar treatment and the lowest it achieved from foliar treatments and the most 1000-seeds weight obtained from foliar application with cycocle. In addition to the uppermost dry matter yield, grain yield and nutrients content obtained from foliar application of uniconazole + cycocle. But foliar treatments hadnt significant influence on harvest index of millet.

Geostatistical techniques were used to describe the spatial distribution of weeds, under conventional management conditions and theirs effect on wheat biomass production over the course of one growing season (2008-2009), in a wheat (Triticum aestivum L.) field at Research Station of Shahrood University, Iran. Weeds Seedling were identified and counted at 121 points of field based on two intervals including prior to and after post-emergence control. Wheat biomass dry weight was determined at the same places of weeds. In the field, 12 weed species were identified. The semi-variogram analysis indicated that 67.4% to 99.8% of the variation of sample density was due to spatial dependence, which suggests that most of the weed species were patchy. Wheat biomass dry weight showed spatial patterns on the field. Cross-semivariograms analysis showed strong (89 and 87.4% in the first and second stages of sampling respectively) spatial continuity between wheat biomass dry weight and weed density patterns on the field. The maps of total weed species corresponded visually to map of wheat biomass. As a result, patchy distribution of weeds can cause spatial heterogeneity in crop biomass production.

In order to compare different weed management methods in sugar beet, an experiment was conducted at the Agricultural Research Station, Ferdowsi University of Mashhad, Iran, during 2006-2007 and 2007-2008. The experiment designed as a Complete Randomized Block with three replications. The treatments including: Metamitron + Fenmedifam, Metamitron + Fenmedifam + rotation, Metamitron + Cultivation, Metamitron + Cultivation + rotation, Disk + fenmedifam, Disk + fenmedifam + rotation, Disk + cultivation, Disk + cultivation + rotation, Covercrop + Fenmedifam, Covercrop + Cultivation, Hand-Weeding and Hand- Weeding + Fenmedifam. In the first year, apart from rotation treatments, the highest and Lowest weed density were obtained in Disk + Cultivation (33 plant.m-2) and Hand-Weeding + Fenmedifam (20.1 plant.m-2). In this year maximum amount of weed dry matter was seen in Disk + Fenmedifam with 89.2 g.m-2 and minimum dry matter of weed was showed in Hand-Weeding + Fenmedifam with 22.2 g.m-2. In second year maximum and minimum weed density were showed in Metamitron + Fenmedifam with 142.6 plant.m-2 and Hand-Weeding with 21.5 plant.m-2, respectively. In this year highest and Lowest dry matter of weed were obtained in Metamitron + Fenmedifam and Hand-Weeding + Fenmedifam with 204 and 30.3 g.m-2, respectively. In first year maximum and minimum sugar beet yield were obtained with Hand-Weeding and cover crop + Fenmedifam with 114 and 43.6 ton per hectare, respectively. In second year highest and lowest sugar beet yield were obtaned with Hand-Weeding and Metamitron + Fenmedifam with 94.4 and 28.3 ton per hectare, respectively. Maximum sugar contains in first and second year were obtained in Disk + cultivation (19.7) and Disk + Fenmedifam (18.3).

In order to evaluate the effects of nitrogen fertilizer on yield, yield components and dry matter remobilization of different rice genotypes, a field experiment was carried out at the farm of Ramin Agricultural and Natural Resources University (Ahwaz/Iran) during 2007. Experiment was arranged in a split plot based on randomized complete block design with three replications. Four nitrogen fertilizer rates (0, 100, 135 and 170 kg.ha-1 from urea source) as the main plots and three rice genotypes (Champa, Anburi and LD183) as the sub plot were the treatments. Results showed that interaction between genotype and nitrogen fertilizer rates had significant effects on paddy yield and dry matter remobilization. LD183 had the highest paddy yield in 170 kgN.ha-1 (6955.81 kg.ha-1). The highest and the lowest amounts of total shoot dry matter remobilization obtained from LD183 in 0 kgN.ha-1 (844.95 kg.ha-1) and Anburi in 100 kgN.ha-1 (230.15 kg.ha-1), respectively. Results also showed that contribution of stem part in dry matter remobilization was 0.03-12.99% while it was lower than 0.5% and 2% in flag leaf and other leaves, respectively. Dry matter remobilization of stem, total shoot and other leaves had a significant and positive correlation with grain yield (r=0.84**, r=0.78** and r=0.5** respectively). It seems that dry matter remobilization have an important role in rice grain filling.

In order to study the effects of supplemental irrigation and planting arrangement on yield, yield components and water use efficiency (WUE) of Kabbuli chickpea (cv. Arman), an experiment was carried out at the Agricultural Research Station of Gonbad for two years, Iran. The experiment was a split-plot factorial arranged in a Randomized Complete Block Design with three replications. The main plots consisted of four irrigation applications: once at the flowering (I1), once at grain filling (I2), twice, one at the flowering and one at grain filling (I3), and rainfed condition (RF). Combination of planting densities (20, 32 and 44 plants per square meters) and rows spacing (25 and 50 cm) were as sub plots. The combined analysis results revealed that all traits were significantly affected by year. None of the traits studied were significantly influenced by simple effects of irrigation or row spacings. All the traits, but 100 grain weight and number of grains per pods were significantly affected by irrigation and row spacings interaction. The effect of irrigation on seed yield did not follow the same trend in two years. In the first year that sum of rainfall was low, RF and then I2 with 3.2 and 2.5 (t/ha), 8.3 and 5.1 (Kg seed/mmwater.ha) and 46.0 and 38.4 (%) and in the second year with I2 with 2.1 (t/ha), 4.0 (Kgseed/mmwater.ha) and 28.7 (%) had the highest seed yield per hectare, WUE and harvest index, respectively. It shows the importance of the time when the rainfall occurs. Therefore based on the increase in yield, irrigation at grain filling might be suitable. Twenty five-centimeter-wide rows out yielded the 50-cm-wide rows in both years. In the fist year, decrease in row spacing significantly inceased grain yield around 400 kg /ha. In the second year, 20 plants m-2 produced higher yield than those of other plant densities.

Drought stress is one of the most important dangers for increasing the yield and good production of crops in Iran and the world. To evaluate the genetic diversity of rapeseed genotypes, identifying the drought resistance indices and drought tolerant genotypes, 16 genotypes were tested in a randomized complete block design (RCBD) with three replications and two different water regimes (Irrigated and rainfed) in experimental field of college of Agriculture, Razi university in 2007-2008. In this research, most of drought tolerance indices such as stress susceptibility index (SSI), tolerance index (TOL), stress tolerance index (STI), yield index (YI), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (HAM) and yield stability index (YSI) based on grain yield were calculated in two different irrigiation regimes. Analysis of variance for grain yield indicated that there was highly significant differenceswere highly significant differences between the genotypes for Yp, Ys, and index GMP, STI, YI and MP. Bi-plot diagram based on two principal componentcomponents indicated that genotypes number 8, 7, 4, and4, and 1 are next to vectors of MP, GMP, STI and HAM and distribution of genotypes in biplot represented the genetic diversity among genotypes for selecting them based on drought tolerance. According to results of drought tolerance indices, Dante, SLM-O46 and Sahara cultivars have higher grain yield and STI index than other genotypes in two regimes and identified as suitable cultivars for production in drought stress condition.

According to the contradictory reports of researchers, tillers may have positive or negative effect on wheat yield. Thus, this study was conducted to investigate the role of tillers on wheat yield under two row spacing of 12.5 and 25 cm and four plant densities of 125, 250, 375 and 500 plants per m2, at Gorgan University of Agricultural Sciences and Natural Resources farm in Anbare-Ololum reign in rainfed and saline conditions during 2008-09. The results showed that increasing of row spacing had no effect on fertilized tillers number per m2, but increased total dry mater, total grain yield and main stems grain yield (about 200 kg) per ha-1. The plant density increasing, increased number of fertilized spikes per m2, total dry mater and grain yield per ha-1. Also main stems grain yield in 375 plant density per m2 was about 120% higher than 125 plants per m2 and more plant density increasing had no significant effect on it. On the contrary, plant density increasing reduced tillers grain yield and main stems harvest index. The interaction between row spacing and plant density on tillers number per m2, fertilized tillers percentage, tillers and main stems dry mater contribution showed that there was highest difference between two row spacing on 250 plant density per m2 and the deference between two row spacing reduced with more plant density per m2. But the difference of tillers harvest index between to row spacing was higher in 125 plant density per m2. In generally, the results showed, in this study, tillers had negative effect on wheat grain yield, Therefore, in this condition, relying on tillers production that results to not optimum using form valuable resources, specially moisture, is wrong. Consequently, for preventing of these wastes of resources, increasing plant density up to 375 plants m-2 and using of row spacing of 25 cm, will reduced tillers dry mater contribution and will result to less moisture wastes form tillers, on other hand, more moisture will remain for main stems and will result in maximum Resource use efficiency and grain yield.

In order to investigating the effects of planting date and harvest time on the quality performance of pear millet, an experiment was conducted in agriculture research station of Gorgan in a randomized complete block design with four replications and factorial arrangement. This experiment included five planting dates (may 5th, may 25th, june 14th, july 4th, july 24th) and three harvest times (90, 110 and 150 cm). The results showed that planting date and harvesting time (in terms of plant height) had significant effect on protein, NDF, ADF and ash content of forage (P<0.05). Planting date also had significant effect on phosphor, calcium, fat and fiber content (P<0.05). The interaction effect of study factors on crud protein, fat and ash content, also, was significant. In the first and second planting dates, just fiber content affected significantly (P<0.05), but with delay in planting time, all measured characteristics decreased (P<0.05). Effects of harvest time were different, and harvesting time (in terms of plant height) had no significant effect on fat, phosphor and calcium content. Total protein content (protein yield) of forage in plant height-based harvest time (90, 110, 150 cm) were 2585.3, 2635.2 and 2876 kg ha-1, respectively. In this case the last one had significant difference with other ones (P<0.05). Mean ADF, NDF and ash content of forage were higher in 150 cm harvest time than other harvest times (P<0.05). Final results elucidate that delayed sowing can decrease forage quality. Harvesting when plant height is reached to 110 cm is advised as the best harvesting time to achieve more quality yield (quality trait (%)×biological yield). Undoubtedly, if we aimed to achieve more quality in expense of less biological forage yield, the harvesting is advices to done when plant height is shorter (90 cm).

For evaluation the effect of morpho-physiological parameters on yield and yield components of barley genotypes, an experiment was conducted in a randomized complete block design in 4 replication in Gorgan Agriculture Science and Nature Resource field experimental during 2006-2007. The trait was 10 barley genotypes: Bomi, Torkaman, Eize, Siah, Sahra, 1-yeknavakht, 14G, 11G, 5G and 15G. The Results showed that there is no significant difference in grain yield in these genotypes. Growth indices with grain yield and yield components had positive correlation. Evaluation genotypes considering total dry matter and growth parameter showed that modern and modified genotypes, had higher leaf area index, and for that they have higher crop growth rate, net assimilation rate and total dry matter in period of growth season.

To study the effects of below leaves excision and nitrogen application on stomatal characteristics of wheat flag leaf, grain protein, dry matter remobilization, grain yield and yield component, leaf area of winter wheat (T. aestivum cv. Ghods) was artificially reduced under filed condition. The experimental design was a factorial on a RCB with 3 replications, a combination of three levels of defoliation (D0= control or intact plants, D1= excision of all leaf blades except flag leaf at booting stage, D2= as D1 but at anthesis stage) and two levels of nitrogen treatment (none and 250 kg ha-1 urea fertilizer at jointing stage) were randomly assigned to plot units. Deficient irrigation was induced from late booting stage until plant maturity. Results showed that defoliation increased the photosynthesis rate (Pn), photosynthetic water use efficiency (WUEp) and dry matter remobilization from stem. The highest photosynthesis rate was observed in defoliated plants at anthesis stage with application of nitrogen. Defoliation significantly decreased the grain protein. Nitrogen application in all defoliation levels significantly could improve Pn, chlorophyll content, grain protein percentage and dry matter remobilization. Leaf area manipulation could not affect grain yield significantly. However nitrogen application could increase fertile spike number per square meter as a yield component.

Terminal heat stress in Mediterranean climates like Ahwaz is reduced Wheat yield. In order to study effect of terminal heat stress on yield and yield components of 20 spring bread wheat cultivars, an experiment was conducted in Ramin University of agricultural and natural resources, Ahwaz in 2007-2008. The experimental design was stripe block design in randomized complete block design with three replications. The experimental factors were four sowing dates (6 Nov., 6 Dec., 5 Jan. and 4 Feb.) in horizontal plots and 20 spring wheat cultivars in vertical plots. The results showed that sowing date, cultivars and its interaction had significant effect on all experiment traits. Means comparisons of interaction effects showed that maximum grain yield (7.039 t/ha) produced by Chamran cultivar in sowing date of 6 Dec. and minimum grain yield (1.219 t/ha) produced by Falat cultivar in sowing date of 4 Feb.

In order to investigate effects of plant density and fertilizer rates on agronomic characteristic and yield Tobacco (Nicotiana tabacum) (cv K326) an experiment was conducted in the experimental field of Tirtash Research and Education Center. Design of experiment was randomized complete block with factorial arrangement with three replications and 36 treatments conducted in 2007 year. Treatments were the combination of the levels of Plant density in three levels (16600, 20000 and 25000 plants/ha) (A), Ammonium nitrate in two levels (100 and 150 kg/ha) (B) Triple super phosphate in two levels (50 and 100 kg/ha) (C) Potassium sulfate in three levels (200, 300 and 400 kg/ha) (D). The results showed that the effect of plant density (A) on the leaf height, leaf width, plant height, stem diameter and Dry matter of leaf was significant in %1 level. Interaction of B×C×D factors was significant on leaf width in %1 level and also interaction of C×D×A on number of leaf and plant height in %1 level and on stem diameter and leaf height in %5 level were significant.