Effect of Soybean and Wheat as Cover Crops on Corn Yield and Weed Control using Different Fertilizer Sources

Introduction: According to the importance of corn in supplying the human food directly and indirectly, it is one of the most important plants among crops. One of the major problems in corn production systems, is competition with weeds that reduce corn yield significantly. Weeds not only reduce crop yields but also decrease the commercial quality and the feeding palatability of main crops. They enhance the soil seed bank of weeds, which may cause continuous weed infestation of field crops as well. Herbicide application is a reliable and highly effective method for weed control. However, demand for safe food products that have been produced with a minimum application of chemical inputs is increasing. Therefore, farmers interested in weed management have to rely on other control approaches. An alternative weed control method is the use of cover crops, which can suppress the growth of weeds by preventing them from light and by producing allelopathic compounds. Cover crops successfully have been integrated into conservational agriculture systems in many areas of the world. Legumes are used as cover crop because of their rapid growth, in addition their potential to provide further nitrogen,along with high ability to compete with weeds. Materials and Methods: In order to study the effect of cover crops (soybean and wheat) and different fertilizers sources on yield of corn and weed control, a filed experiment was conducted in randomized complete block design with three replications in 2012. Treatments included two cover crop (wheat and soybean) and three fertilizer (no fertilizer, chemical fertilizer and compost)..Fertilizer treatments was used according to soil analysis and requirement of corn (as a main plant). Weed-infestation and weed-free plots were used as controls. Study cultivars of corn, wheat and soybean were NS-640, Milan and Sari, respectively. Planting of corn was in June and cover crop was planted with corn simultaneously and between corn rows. The dominant weed species were velvetleaf (Abutilon theophrasti Medic.), johnson grass (Sorghum halepense (L.) Pers.), wild melon (Cucumis melo var. agrestis) and giant foxtail (Setaria glauca L.) in the field. In order to determine the dry weight and density of weeds, three-stage sampling was performed from the middle rows of corn. Corn yield was also measured by mechanical harvesting in middle rows and adjusting to 14% moisture. A week before the final harvest, ten plants of corn were selected randomly from the three middle rows of each plot and yield components including the number of rows in corn, number of kernels per row, weight of 1000 grains was measured. Results and Discussion: The results showed that soybean cover crop reduced weed density compared to control in weed infestated plots, but wheat was not successful in suppressing weeds and reducing their density due to poor biomass and dying at the end of growing season . So, the lowest dry matter of velvetleaf, wild melon and other weeds were related to planted corn with soybean and compost and the maximum was related to monoculture of corn with weed infestation. Results of analysis of variance indicated treatments had significant effect on grain yield. The lowest yield of corn (2733.3 Kg ha-1) was in weed-infestation control while the highest one (12124.0 and 8351.3 Kg ha-1 respectively) was in weed-free control and soybean’ cover crop plus compost. For both cover crops between fertilizer treatments, compost and chemical fertilizer had more corn biological yield than no fertilizer and differences between this two fertilizer treatments wasn’t significant. Reduction of yield under no fertilizer treatments was due to competition for nutrients, light between weed and corn. The maximum and minimum number of rows in corn and number of kernels per row respectively was obtained with monoculture of corn in weed free and weed infestation, while the maximum weight of 1000 grains was observed in soybean with applying compost. Generally, the living mulch as cover crops can reduce competition between weeds and the main crop. Conclusion: As cover crops reduce weeds growth, and there was no significant difference between chemical and organic fertilizer in corn yield, so we can use these two options for producing optimum yield in sustainable agriculture. Results showed application of soybean as cover crop, especially integrated with organic fertilizers, can be an alternative approach for herbicides and are more effective than the others

A Study of Intercropping of Maize with Sweet Basil and Borage

Intercropping is one of the environmental friendly ways to improve the use of resources and weed control. A field experiment was performed on maize intercropped with sweet basil and borage under weed free and infestation conditions. The experimental design was a factorial based on randomized complete block design with three replicates. Factors included weed infestation levels (weed free and weed infestated) and intercropping ratios (100:0, 75:25, 50:50, 25: 75, and 0:100, maize: sweet basil or borage). The intercroppping treatments decreased weeds biomass compared to the monocultures of borage and sweet basil. The weeds biomass and density in maize monoculture was lower than the monocultures of the other two plants. Under sole crop condition, the plants yield was higher than intercropping treatments. Weed interference decreased the yield of plants, while this decrease was less in intercropping treatments. Area-time equivalent ratio value showed that the ratios of 50:50 maize: sweet basil, maize: borage and 25:75 maize: borage provided the yield advantages of 11%, 11% and 36% under weed infestation, respectively. Also, area-time equivalent ratio values were higher in weed infestation compared to weed free treatments. The leaves essential oil of sweet basil under intercropping treatments, especially in weedy condition, was further than monocropping treatments. Intercropping of maize with sweet basil was more successful than intercropping with borage in reducing weeds biomass and density. In general, the intercropping of maize with sweet basil was more efficient compared to intercroppping with borage

Determination of Cardinal Temperatures and Phenological Stages of Two Species of Spiny Cocklebur (Xanthium spinosum) and Common Cocklebur (X. strumarium) Based on Growing Degree-Day

Two species of common cocklebur (Xanthium strumarium L.) and spiny cocklebur (X. spinosum) are common annual summer weeds in soybean fields and other summer crops. The current research was carried out with the aim of determining the cardinal temperatures of germination and determining the phenology stages of these two species in Sari University of Agricultural Sciences and Natural Resources. In order to determine the cardinal temperatures of germination of seeds of two weed species, the seeds were examined at constant temperatures of 5 to 45 °C in a completely randomized design in 4 replications in a laboratory experiment. Also, the phenology stages of two weed species were investigated in a field experiment. The highest germination% was observed for the spiny cocklebur (51.3%) and the common cocklebur (58.1%) at temperatures of 25 and 35 °C, respectively. According to the different parameters of segmented model, the base temperature, lower optimum temperature and ceiling temperature for spiny cocklebur are 1.4, 23.2 and 54.7 °C, and for common cocklebur are 4.8, 34.6 and 48.4 °C, respectively. Time from emergence to physiological maturity for the spiny cocklebur and common cocklebur were 136 and 128 days, respectively. The results suggested that seed germination of the two weed species occurs in a wide range of temperatures, i.e. of 5 to 45 °C, and the best time to control this weed is late summer (before the beginning of the flowering stage)

Unity is strength: A study of supplier relationship management integration

Researches on the supply chain management within the last decade demonstrate that business processes integration can increase the performance effectiveness and efficiency across the chain. This study intends to investigate the integration of the supplier relationship management (SRM) process between the manufacturer and its first upstream tier of suppliers within the construction equipment industry. This research also strives to identify the potential obstacles to the SRM integration and provides solution suggestions to overcome these barriers. In this regard, the review of the literature and subsequent analyses of the empirical findings from European construction equipment manufacturers illustrate that the SRM process integration can take place through the integration of its several sub-processes into strategic and operational characteristics. In this context, the lack of goal congruence, commitment, and trust between the manufacturer and its supplier are the major potential barriers to the SRM integration

When customer involvement hinders/promotes product innovation performance: The concurrent effect of relationship quality and role ambiguity

Despite recent attempts to explain the nature of customer involvement, the question of how to curb its negative effect on product innovation has yet to be explored. This study focuses on the association between customer involvement and developers’ product innovation performance, and relies on relationship management theory and the role hazard perspective to explore what levels of relationship quality and role ambiguity, which coexist in partnerships, can turn ineffective customer involvement into a successful strategy. Using a survey of 273 manufacturing firms, we found an inverted U-shaped relationship between customer involvement and product innovation performance, and verified that the interplay of relationship quality and role ambiguity significantly moderate this association. We unpack the role of our moderators by developing a 2 × 2 matrix of high versus low levels of role ambiguity and relationship quality, and exploring the nature of the association between customer involvement and product innovation performance in each quadrant