To investigate the response of corn to combined application of chemical fertilizers with rhizobacteria plant growth promoting, an experiment was conducted in 2017 at Research farm of Agricultural and Natural Resources Campus of Tehran University, Karaj, Iran, in a randomized complete block design with four replications. Four nutritional treatments including T1 (Control treatment without applying fertilizer), T2 (Just PGPRs), T3 (Use chemical fertilizers based on soil test) and T4 (T3 + PGPRs) were considered. According to the results, the highest total dry weight (3.9 kg/m2), crop growth rate (79.8 g.m-2.day-1), net assimilation rate (15.3 g.m-2.day-1) and grain yield (18.2 ton.ha-1) were observed in T4 treatment and T2 treatment produced the highest  leaf area index (5.3), leaf area duration (205.2) and specific leaf weight (78.5 g.m-2) . Also, the lowest value of all traits was observed in in T1 (control) treatment. The results showed that the presence of rhizobacteria plant growth promotioninduction in the corn nutrition program increased the growth and growth indices of the plant. Combined application of chemical fertilizers with rhizobacteria plant growth promoting resulted in the highest growth and final grain yield of corn.

One of the most important environmental factors affecting agricultural production, climate and small-scale man Spending it can control costs is costly.So the only way to tackle climatic limits the cognitive constraints in terms of coping with them and the crop is managed. The present study for corn cultivation Zoning in Lorestan province, the climatic elements of temperature, relative humidity, and degree days of the ten synoptic stations in the Lorestan province additional environmental parameters were used for slope and soil PH. Among the important factors in temperature due to its more importance in degree of phonological form was investigated, then the zoning maps for the production of these crops GIS techniques were used. After the initial production of maps for definition matched layers and influential areas of fuzzy standard method were used. Finally, in order to integrate data based on the weight of the evaluation hierarchy (AHP) was used to map land prone Zoning corn planted in Lorestan province, respectively. Zoning results using these methods showed that 2.34 percent province, an area prone to these crops, 8.55 percent semi-prone, poor and 13.08 percent in 76.03 percent in province with poor conditions where results indicate is most desirable places in the West region, central and northern parts of the province are scattered.

An experiment was carried out to evaluate the competitive effects of lambsquarters (Chenopodium album L.) on corn (Zea mays L.) grain yield, in Tabriz in 2008. Factorial experiment was established on randomized complete block design with three replications. Factors were five weed densities (1, 4, 8, 12 and 16 weeds m-1 of row) and four relative times of weed emergence (emerged with corn; 10, 20 and 30 days after corn emergence) including a weed free. Interaction of lambsquarters density and time of emergence on weed leaf area index at 75 days after corn emergence was significant. Leaf area index in weed ranged from 2 in the highest to 0.19 at the lowest competitive condition. With increasing of weed density and delaying in emergence time its biomass reduced. Weed competition was caused a significant loss in grain yield and time of weed emergence is more effective than weed density. Yield loss of corn at different weed emergence times were 64%, 38%, 15%, 8%; and at different weed densities were zero, 23%, 35%, 46%, 53%, respectively, compared with control. Emergence of minimum four lambsquarters plants per meter of corn row before 20 days after crop emergence and competition until late growth season was the economical threshold of this weed.

The use of green cover temperature for plant irrigation planning is one of the methods that has been considered by researchers. For this purpose, several indicators have been presented, among which we can mention the water stress index of the plant by Idso method. In order to plan summer corn irrigation in climatic conditions of Ahvaz using green cover temperature, in 2018 research in the research farm of Shahid Chamran University of Ahvaz Faculty of Water Engineering under four types of irrigation regime including I0, I1, I2 and I3 respectively 120, 100, 80 and 60% of the plant's water requirement was done in a completely randomized design in three replications. Based on the results, the equation of the upper and lower base line for the corn plant, treatment I1 (100% water requirement) for the development stage is 2. 89 and (Tc-Ta) ll = 1. 984-0. 0946VPD, for the middle stage is 3. 4 and (Tc-Ta) ll = 3. 217-0. 1669VPD and for the final stage of growth was equal to 1. 2 and (Tc-Ta) ll = 1. 147-0. 160VPD was obtained in degrees Celsius. The results also showed that the total water stress index for the growth period for the 120, 100, 80 and 60 treatments was 0. 17, 0. 22, 0. 35 and 0. 52, respectively. The relationship between plant water stress index and soil moisture level for different irrigation treatments was highly correlated and the equation of soil stress index with soil moisture for I1 treatment for the next day and before irrigation was equal to CWSI = 1. 8296-0. 0586ɵ, v and CWSI = 1. 038 0. 0281ɵ, v was obtained. The results showed that with decreasing water consumption, the plant's water stress index increased and with increasing water stress, the correlation between CWSI index and soil water depth decreased so that the highest R2 (0. 97) in I0 treatment and the lowest R2 (0. 88) was in I2 and I3 treatments. As the results of this study confirm, the plant's water stress index is a good tool for irrigation planning and optimal management in the field.

In order to investigate evaluate the relation of physiological to corn grain yield an experiment was conducted in Arsajan of Fars in 2009. The experiment was in factorial using randomized blocks design consisting of corn hybrid in 6 levels (704, 504, 666, Maxima, Zola and Jeta) and 3 densities (4, 8 and 12 plants m-2).The results showed that there was significant difference between corn hybrids.The highest grain yield was observed in 504 followed by 704 and 666 and the lowest yield observed in Jeta. There was no significant difference between planting densities but different hybrids showed different responses to changing densities. The highest LAI was observed in 704 and 504 and highest CGR observed in 504. In addition 666 and 504 had high RGR values that imply positive roles of these physiological traits in grain yield. Physiological traits responses in corn hybrids were changes with different density, as high yielding hybrids in low to optimum densities showed better yield physiological performance.

In order to investigate genetic correlation and path analysis between grain yield and yield components, fifteen early maturing hybrids of grain corn (Zea. mays) using a randomized complete block design with 4 replications were evaluated in Khoramabad agricultural research center, Iran. The data were collected and analyzed for ear emergence date, anthesis date, maturity date, plant height, ear height, plant stand, ear cover, grain number per row, row number per ear, grain depth, 1000- grain weight, plant value, cob percent, grain yield, stay green, stem and leaf resistant to disease. The results showed grain yield was positively correlated with plant height, ear height, grain depth, row number per ear, grain number per row, but negatively with 1000-grain weight, ear cover, cob percent and stay green. Between emergence date and maturity date and It was observed significant negative correlation stay green and leaf disease and  positive significant correlation with ear height, grain depth and ear cover, suggested that late maturing hybrids with higher productivity were more resistant to diseases. The results of regression and path analysis showed that 1000-grain weigh and cob percent were correlated with yield negatively, and grain depth, plant height and plant stand were positively (R2=0.52) and had higher effects on grain yield.

Introduction: Corn grain represents the most important energy source in ruminant diets. In high-producing dairy cows, the diets contain high levels of corn in order to meet their energy requirements. Corn has a complex structure where a range of nutrients interact with each other or physically associations. Ultimately, the quantity and availability of these nutrients determines the nutritional value of this grain. In corn nutrients and energy utilization is influenced by both intrinsic (e. g. starch granules and protein matrix structure) and extrinsic (e. g. growing and storage conditions, climate and agronomy conditions and grain drying process) factors. Corn endosperm represents more than 80% of total grain and is composed of starch granules that are imbedded in a protein matrix and surrounded by plant cell walls. Starch granules size, starch composition (amylose/amylopectin ratio), starch encapsulation (by endosperm cell walls and protein bodies) are among the factors with the most influence on digestion of starch. The structure and distribution of starch and protein matrix network of grains vary in different corn varieties. The Objectives of this study were to evaluate physical and chemical properties, gas fermentation parameters, starch digestibility and starch granules structure in Iranian corn grain Single cross 702 in comparison with different kind of imported corn grains (Russia, Ukraine and Brazil). Materials and methods: Corn grain samples (Single cross 702, Russia, Ukraine and Brazil) were obtained from Khorasan Razavi Agricultural and Natural Resources Research Center, Mashhad, Iran. The apparent density was measured and the samples were analyzed for DM, OM, CP, EE, NDF, ADF, starch. Gas production was conducted in a 125 ml amber flask with three series of incubation. Gas production parameters were calculated. Also, rumen, intestine and total tract digestibility of DM, starch and CP were determined by using the in situ mobile bag procedure. Different parameters of damaged starch (the absorption of iodine, Ai%; damaged starch content in UCD, Chopin units; UCDc, Chopin units on protein basis matter) were determined using the amperometry method (Chopin, ZI Val de Sein, 92390 VLG, France). Starch gelatinization was determined according to the enzymatic procedure (AACC Method 76-31. 01; K-SDAM, 09/2018). Scanning electron microscope (LEO 1450 VP, USA), at an accelerating voltage of 25 kV, and under 2500x magnification to study the grain structure was done. Data were analyzed by GLM procedure of SAS with a completely randomized design. Results and discussion: Apparent shape of Single cross 702 was smaller than other corn varieties. Apparent density was higher in Brazil corn than other corn varieties. DM, OM and EE were not shown significantly difference between corn varieties; however, CP, ADF, NDF, starch, NFC, TDN, NEg and NEl were significantly affected by different corn varieties. Starch in Single cross 702 corn (69. 03%) was significantly lower than Russia (71. 04%), Ukraine (70. 36%) and Brazil (71. 49%) corns. Asymptote gas production (A) was not influenced by different corn varieties; however, the real gas production in time 24 and 48 h incubation in Brazil, Russia and Single cross 702 corns was greater than Ukraine corn. The instant rate of gas production until 8 h incubation in Single cross 702 and Russia corns was greater than Ukraine and Brazil corns. The time for fermentation of 25 and 75% of substrate in Single cross 702 and Russia corns were significantly reduced than other corn varieties. The PH, NH3-N and total VFA of bath culture in 24 h didn’ t influence by corn varieties, however acetate to propionate ratio in Brazil corn was greater than other corns. In spite of that the rumen starch digestibility of Single cross 702 (61. 59%) and Russia (59. 51%) was increased than Ukraine (45. 31%) and Brazil (40. 51%) corns; however, Ukraine (97/. 06%) and Brazil (98. 39%) corns showed the intestine starch digestibility greater than Single cross 702 (93. 79%) and Russia (93. 87 %) corns. The starch gelatinization in both of Single cross 702 (4. 24%) and Russia (4. 17%) was greater than Ukraine (3. 78%) and Brazil (3. 32%) corns. The scanning electron microscopy showed that the starch granules size was not uniform in the Single cross 702 corn and the number of small starch granules was greater than other corn varieties. Also, the thin protein matrix was observed in the Single cross 702 corn. In contrast, the starch granules size in the Russia and Ukraine corns were larger and uniform. In Brazil corn, the starch granules were arranged with greater density and a non-smooth surface was observed on the granules. Many studies were done on nutrient value of different corn varieties. Numerous factors can affect the grain chemical composition, physical properties and starch availability on corn grain that include cell wall structure, type of endosperm (floury or vitreous), starch granules and protein matrix, genetic and environment. Corns contain higher floury to horny starch ratio showed greater starch gelatinization and greater starch digestibility in the rumen and total tract. Findings of this study represent the Single cross 702 and Russia corns showed higher gas production, rate of gas production, starch gelatinization and rumen digestibility of starch than Brazil corn. Conclusion: It is concluded that the Single cross 702 corn in terms of flurry endosperm, gas production, gas production rate, starch gelatinization and rumen digestibility of starch was similar to Russia corn, although the structure of starch granules was different. Brazil corn had a horny endosperm and showed lower rate of gas production in initial hours of incubation, lower starch gelatinization and higher intestine digestibility of starch than other corns. It generally seems that the result of this study and similar studies can offer useful information about corn grain for farmers and the animal feed manufactures for processing of corn.

To evaluate the effect of nitrogen and water withholding in vegetative growth stage of corn on efficacy of nicosulfuron and 2,4-D+ MCPA an experiment was conducted as a factorial arrangement in a randomized complete block design with three replications at Tarbiat Modares University in 2017. The first factor contained four treatments including application of nicosulfuron, 2,4-D+ MCPA, weed free and weed infested as control. The second factor consisted of normal irrigation and water withholding from 4 to 8 leaf stage. Third factor contained either urea application or no fertilizer application. Normal irrigation and nitrogen fertilizer application significantly increased nicosulfuron and 2,4-D+ MCPA efficacy in weed control and total weed dry weight decreased to 341 and 361 g.m-2 respectively compared 1370 g.m-2 as weed infested. Nicosulfuron and 2,4-D+ MCPA reduced weed total dry weight significantly under irrigation withholding. Grain yield increased with application of nitrogen and nicosulfuron. Grain yield was higher with application of 2,4-D+ MCPA than nicosulfuron without nitrogen application under irrigation withholding. Application of nicosulfuron with nitrogen application provided satisfactory weed control and increased grain yield.