نشریه یافته های نوین کشاورزی
سال دوم شماره 2 (پیاپی 6، زمستان 1386)

In order to study the effect of plant densities on morphological characteristics and seed yield of soybean cultivars in Markazi province an experiment was conducted in agricultural researches center of Arak in 2007. The experimental design was split plot arrangement in a randomized complete blocks design with three replications. The treatments included two factors, plant densities in four levels (16, 22, 28 and 34 plant/m2) as main plots and two soybean cultivars and line (Williams and L17) in subplots. Results showed that the effect of plant density on number of lateral stems, pods per plant and 1000 cernel weight was significant at 1% level. The effect of density on yield was significant at 5% level. Interaction of density cultivars was negligible on all studied traits except 1000 seed weight (at 1%) and grain yield (at 5%). Result also showed that the highest and lowest yield were obtained at D4 (34 plant/m2) and D1 (16 plant/m2) with 3880 and 3350 kg/ha respectively. The yield of L17 was 3980 kg/ha that higher than Williams with 3390 kg/ha grain yield. The highest yield was obtained with L17 at D4 density (4490 kg/ha) and the lowest yield was recorded with Williams cul in D1 density by 3010 kg/ ha. The D1 and D4 produced the highest (8) and lowest (3.3) lateral branches per plant respectively. The maximum number of pods per lateral branches was recorded at D1 and the minimum at D4, by 6.51 and 4.33 respectively. The highest (42.5) and the lowest (21.41) pods per plant was produced by D1 and D4 respectively. The average 1000 cernel weight at L17 was 152.42 gr. which higher than Williams with 147.42 gr. Maximum 1000 cernel weight was recorded in L17 at D1 density (160 gr) and the minimum 1000 cernel weight obtained with Williams cul. At D4 (136.3 gr) There were positive and significant correlation between grain yield and harvest index at 1% level and the number of pods per plant at 5% level.

To study of temperature effects on maize different hybrids yield, yield components and phonological stages, this study were conducted in split-plots based on RCBD with three replications in Islamic Azad University, Jiroft branch during 2004-2005. The sowing dates (including 1 and 16 July, 1 and 16 August), and hybrids (ZP434, BC404, OSSK444, BC504, KSC500, G3337, NS540, BC666, BC678, KSC704, G3393 and KSC700) were selected as main and sub-plots, respectively. Results showed that year and sowing date had not significant effects on summer maize grain yield in this region. Although, one month retarding of sowing date (16 July - 16 August) were caused the yield decreasing by 3.9%, but this effect was not significant. Hybrids had significance effects (P<0.01) on maize seed yield and BC678, BC666 (belongs to FAO600 by 11.489 and 11.404 ton/ha), KSC704 and G3393 (belongs to FAO700 by 11.253 and 11.110 ton/ha) have the highest grain yield. Effects of sowing date on yield components were not significant, while hybrid's effect were significant (P<0.01). Grains/row was significantly affected by sowing date and studied hybrids had significant effects on yield components. BC678 (37.8) and KSC704 (37.8) and KSC500 (29.5) had maximum and minimum grains/row, respectively. Required growth degree days (GDD) from sowing until tassel formation, pollination and silk appearance at 5% probability level and requisite GDD from sowing until emergence and maturity in 1% probability level were significant.

In order to evaluate noduling and nitrogen fixation as well as efficiency of Rhizobium Japonicum strains in Clark cultivar of Soybean under drought stress and also efficiency of Rhizobium Japonicum strains. Experiment performed in 2003 and 2004. Experiment conducted under split plot based on randomized complete block design with three replications. Irrigation treatments as main plots with tree levels of drought stress, namely low stress (85% plant water requirement), medium stress (70% plant water requirement), high stress (55% plant water requirement) and complete irrigation as control. The subplots were three strains of Rhizobium Japonicum named Helinitro, Rizoking, Nitragen and no bacteria as control were considered. The amount of irrigation water calculated with the help of plant water requirement and the atmometer. Seeds were inoculated with bacteria strains before planting. And then quantity, dry weights and sizes of nodules, nitrogen fixation and also nitrogen fixation yield in area determined. The results indicated that drought stress affected nitrogen fixation. In complete irrigation as Control highest dry weight produced with application of Helinitro strain. Rizoking strain which had active nodules showed higher nitrogen fixation and produced dry weight in low and medium drought stress. In order to access dry mater in complete irrigation using Helinitro and in drought stress, Rizoking were more appropriate. Also results showed that size and weight of nodules were not suitable as an index of nitrogen fixation.

In order to evaluation and determination of the most effective traits in improvement grain yield of bread wheat genotypes, an experiment conducted using 320 genotypes in the research field of agriculture institute of Shahrekord in 2006. Genotypes were cultivated in augmented design along with Karaj1 and Sardari as the check cultivars in both stress and non-stress conditions. Grain yield and 10 related feature of traits were measured in this research. Correlation coefficient analysis showed that in both condition all traits except awn length and in non-stress condition spike weight had positive and significant correlation with grain yield in 1% probability level. By using step-wise regression analysis in stress condition five traits and in non-stress condition three traits entered to the model that verified 97.8% and 96.5% of grain yield variation, respectively. Path analysis for grain yield indicated that in stress condition biological yield, harvest index and grain number per spike and in non-stress condition biological yield and harvest index had the most positive and direct effect on plant kernel yield. Grain number per spike in stress as direct and in non-stress condition as indirect affect positively and significantly on increase grain yield. Therefore, results of research indicate that use of these traits suggest as indirect selection criteria in order to improve grain yield of bread wheat genotypes in both stress and non-stress conditions.

Exploration of ploid levels of citrus plants in the north of Iran which some of them have special charac­teristics, could be profitable in improvement of qualified and fertile citrus cultivars. In this case, six natural hybrids were selected from native citrus hybrids of kotar 10 in Mazandaran related to the center of citrus plants researches of country in Ramsar and were numbered from 7 to 12. These single hybrids have resulted from seeds of a hybrid named kotra 10. Which were studied after the rooting stage. Morpho­logical studies of these hybrids by use of squashing and staining have put them in the same class as Pseudo citrones. The number of chromosomes in all hybrids were determined to be 2n=2x=18. Morphological study of chromosomes in the Pseudo–citron, revealed that they were meta–centric chromosomes with few sub–meta–centric exceptions and relative length of chromosomes varied between 7% to 32% from big to small in all of hybrids. As a result, little differences were detected, in terms of size and morphology of chromosomes. The caryotypical characteristics, considering the homogeneity of the caryotype and the absence Variations among chromosomes in these caryotypes the hybrids will probably have been put in the early stages of evolution of phillogeny.

In order to study the effect of microelements on competition ability, growth and damaging of ryegrass, an experiment was done in 2004–2005 at experimental field of Azad Islamic university of Ahwaz branch. In this experiment, growth of ryegrass and wheat were studied in different conditional feeding including complete microelements (Zn, Cu, Fe, Mn, Mg and Mo) at 1 kg/ha, Zink at 0.5 kg/ha and a control treatment. Different population parameters include innate rate of increase (r) and carrying capacity (K) were calculated and compared according to logistical growth model. Competition effects of two species were studied in different feeding condition according to Lutka and Voltra model. The results showed that application of microelements increase dry weight of ryegrass. Complete microelements could increase dry weight and growth rate of ryegrass more than other treatments. Were as dry weight and growth rate of wheat with microelements utilize decreased because increase competition ability of ryegrass. Also specified that ryegrass had more unfit environmental condition tolerance power than wheat.

Costs of repair and maintenance are most part of the cost of machinery usage. Cost estimation of repair and maintenance of agricultural machinery is very important for replacement and net return of management of machinery. This is an important factor to present a mathematical model for the cost predication of repair and maintenance. The main goal of research was to present a mathematical model of repair and maintenance cost modern tractors in selected province of Iran. In this case New Holland TM155 and Valtra 8400 tractors were selected in Markazi and Fars provinces. First of all a questionnaire including driver's information and technical data for the tractors was completed by randomly sampled tractor driver. In this case 100 questionnaires were distributed between users of each type of considered tractors during spring till summer of 2007. Provided data were analyzed by SPSS and Excel soft wares to do statistical analysis and determining appropriate mathematical models. T test was used to mean comparison of tractor’s cost and Z, F and R2 as statistical test and indexes were done to finding appropriate mathematical models. The average annual repair and maintenance costs of New Holland TM155 and Valtra 8400 were calculated 3304 and 3635 Ri/hr respectively. Results showed that the average repair and maintenance costs of Valtra 8400 were significantly higher than New Holland TM155 tractors at 5% confidence level. In this research appropriate mathematical models were offer to estimate repair and maintenance costs of each models.

Most farmers use fertilizers and herbicides on the basis of their interests and local experience rather than the expert’s recommendations. They use just two kinds of fertilizers, Urea and Ammonium Phosphate. Nowadays, most of them had not enough information about the plant’s common elements such as Potassium and Sulfur and the microelement such as Iron, Zinc and Magnesium have been ignored. In order to behave appropriate against using fertilizers, innovation of "soil test" became important during a last decade. But the present condition shows that there is very difference from it and the expectations. This research was carried out for analyzing technical communicational variables effective in the receptionist of "soil test" by Qom’s cereal planters. It was a survey research and the statistical universe of 2455 farmers was covered guiding and supporting services of the soil test’s innovation that was identified by classification sampling in four areas covered by 184 people when using Kukran’s formula as the samples. Data collection approach was a questionnaire that its validity is confirmed by calculating Cornbach’s alpha coefficient. Results showed that 67.4% of farmer didn’t accept “soil test” as effective factor. The variables related to knowledge level of cereal planter’s in respect with "soil test", the degree of the relationship between the farmer and the information supplier, the common participation level, the individual’s social position, their motion level for farming and job satisfaction, their being able to reach the institutes and their being able to use agricultural and governmental credits have a positive and meaningful relation to acceptance of that subject. The development of a collaboration related to the education unit of jihad Agriculture ministry with the institute relation to educating the cereal planters to be able to write for increasing their studies, using different ways of extension them, such as: holding the exhibition and broadcasting programs related to the importance and necessity of "soil test", their focusing more on companies and agricultural associations and long term and comprehensive planning for the extension workers and experts and continuous relations to the farms for continuous control in this fact that how "soil test" is implemented.