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This research aims to determine the green manure cover crop or crops for cultivation in the second half of summer and after the short-term fallow of the land in the first half of summer and incorporating those crops into the soil two to three weeks before wheat in order to improve the quantitative and qualitative characteristics of wheat. Also, the soil improvement of the test site was implemented during four crop years (crop years 2017-2018 to 2020-2021), so that it can lead to the stability of wheat-based irrigated cropping systems in Alborz province. The project using the statistical design of randomized complete blocks in sixteen treatments including pure cultivation of summer cover crops including pure cultivation of crops: 1- grain sorghum 2- fodder millet 3- Sudangrass sorghum 4- Barley 5- Safflower 6- Mung bean 7- Canola 8- Soybean 9- Cowpea 10- Crimson clover 11- Berseem clover 12- Rye 13- Hairy vetch 14- Oat 15- Sesame 16- Sainfoin and it was implemented in three repetitions. The traits to be measured include: grain yield, straw, biomass and wheat yield components, indicators related to bread quality, physical, chemical and biological soil characteristics of experimental treatments and productivity and economic evaluations of experimental treatments. The results showed that in all crop years, the difference between the effect of cover crops on wheat grain yield was not significant, while the results of composite analysis showed that the effect of experimental years on wheat grain yield was very significant, which shows that sowing Cover crops in the summer before the main wheat crop due to the stability of the experimental units in a medium-term period of time has caused positive legacy effects on the growth, yield and quality of wheat as well as the soil of the experiment site, which is due to a significant increase in the percentage of organic carbon (211 percent) that is, from 0.45% in the first year to 1.5% in the fourth crop year, as well as improving the physical, chemical and biological characteristics of the soil, as well as creating a balance of microbial populations, including bacteria and fungi, and generally improving soil health. The average wheat grain yield in the first years (base year) to the fourth year is 6760, 7767, 8318 and 8380 kg per hectare, respectively, and the highest wheat grain yield in the second, third and fourth years is 9029 kg per hectare, respectively (from sorghum, Sudangrass), 8918 kg/ha (from mung bean and canola) and 9518 kg/ha (from fodder millet) were obtained. Also, based on the results of the AMMI variance analysis model, due to the existence of legacy effects of green manure crops on wheat grain yield, biomass and components of wheat grain yield, the examination of the fitted linear equation showed that without considering other management factors or conditional on their being constant , taking into account the short-term fallow in the first half of summer and the introduction of green manure cover crops and their cultivation in the second half of summer in the lands under the water-based wheat protection cropping system, it is possible to increase the yield of wheat grains in a four-year period from 6744 to 8384 kg per hectare means it has increased by 24% while 97% of wheat grain yield changes under the influence of green manure cover crops can be predicted by the above linear model.
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