Identifying the constraining factors of production and Yield gap is very important. Therefore; this research was performed to identify the production constraining factors of local rice cultivars. All management practices from nursery preparation to harvesting stages for 100 paddy fields of local rice cultivars were recorded through field studies, in Sari, from 2015-2016. In the CPA, the actual and calculated potential Yield were 4495 and 5703 kg/ha, respectively and the gap was 1221 kg/ha. The Yield gap caused by number of top-dressing variables was 324 kg/ha, equal to 27% of the total Yield gap. The Yield gap related to previous year of legumes cultivation was 218 kg ha-1, equal to 18% of the total Yield variation. Among the 10 variables entered in the CPA model, the effects of top-dress fertilizer application and its application frequency and foliar application were remarkable, which could compensate a significant part of the Yield gap (444 kg/ha, 37% of total) in the farmers’ fields by managing these variables. According to boundary line analysis (BLA) finding, actual Yield mean on the basis of optimal limit related to 12 variables under study was 5369 kg/ha, with 881 kg/ha Yield gap . Mean relative Yield and relative Yield gap for 12 variables (transplanting date, seedling age, number of seedlings per hill, planting density, nitrogen and phosphorous per hectare, nitrogen before transplanting, harvesting date, lodging problem, pest problem, diseases problem and weeds problem) were 83.64 and 16.35 kg/ha, respectively. Based on the finding, it can be stated that the model precision is appropriate and can be applied for both estimation of the quantity of Yield gap and determining the portion of each restricting Yield variables.

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.

This study was conducted during summer and winter of 2018- 2019 in the agricultural research field of Shahid Chamran University. Experimental design was split- plot based on RCBD with three replications. The main plot was the type of agricultural system in three levels including conventional (Conv), organic (Org) and sustainable (Sust) (integrated between Conv and Org) and sup- plot was the type of pre- cultivated Crop in sequence with wheat including cultivation of mung bean (M- W), corn (C- W), sesame (S- W) and fallow (F- W). Yield quantity (Yield and its component) and quality (grain protein), an estimate of photosynthesis matter transfer index of wheat and soil organic carbon (SOC) after one double-Cropping were measured. The result showed that the highest (545.04 g/m2) and the lowest (409.28 g/m2) seed Yields were obtained in Conv and Org respectively. In contract, with the changing type of system from Conv to Org, grain protein was increased significantly (from 8.3 to 9.6 %). In addition, the highest (535.47 g/m2) Yield of wheat was obtained from M- W double Cropping. On the other hands the highest remobilization and current photosynthesis matter were obtained in the organic agricultural system with M- W and conventional with M- W double Cropping. The situation of SOC showed that the highest (33.18 mg/g) SOC was obtained in the organic agricultural system with C- W double Cropping. The reason for improving SOC in the organic and sustainable agricultural system was application of organic matter (compost and vermicompost) and Crop residue management. Totally, from the Crop ecology point of view, sustainable agricultural method with a sequence of M- W was the most desirable system.

امروزه سطح کشاورزی حفاظتی در جهان بیش از 180 میلیون هکتار و یکی از مزایای اصلی آن بهبود بهره وری آب است. این تحقیق در باره ی کاشت سویا تحت مدیریت های مختلف میزان بقایا و روش های خاک ورزی روی بقایای گندم است که به صورت کرت های نواری در قالب طرح بلوک های کامل تصادفی در سال های 1389 و 1390 در ایستگاه تحقیقات کشاورزی گرگان اجرا شد. تیمارهای اصلی در سه سطح مدیریت بقایا، شامل 1R: سوزاندن، R2: حفظ 50 درصد بقایا و تیمار R3: حفظ 100 درصد بقایا و تیمارهای فرعی نیز در سه سطح روش های خاک ورزی، شامل T1: خاک ورزی مرسوم (شخم + دیسک + کشت با ردیف کار)، T2: کم خاک ورزی (خاک ورزی حداقل با دستگاه خاک ورز مرکب+ کشت با ردیف کار) و T3: بی خاک ورزی (کشت با کارنده ی بی خاک ورز) است. نتایج بررسی ها نشان می دهد تیمار اصلی R2 و تیمار فرعی T3 بهترین بازده را از نظر تولید داشته اند و عملکرد محصول 47/7 و 17/4 درصد به ترتیب نسبت به R1 و T1 افزایش داشته است. بیشترین و کمترین میزان حجم آب مصرفی به مقدار 3950 و 2690 مترمکعب در هکتار به ترتیب متعلق به تیمار R1 و R3 و حداکثر و حداقل بهره وری آب سویا به ترتیب مربوط به تیمارهای R2 وR1 به میزان 1/13 و 0/55 کیلوگرم بر مترمکعب بوده است. کاشت در شرایط بی خاک ورزی موجب بهبود بهره وری آب سویا نسبت به روش مرسوم به مقدار 15/3 درصد شده است.

In order to investigate the possibility of quinoa producing in Garmsar, Iran, a factorial experiment conducted in randomized complete block design with three replications in 2018-2019 growing season at Garmsar Agricultural Research Station. The factors were planting date at three levels (March 6th, April 1st and April 6th) and the three genotypes of quinoa (Q26, Q29 and Titicaca). Results showed that the effect of planting date was significant for all studied traits except the harvest index. Also, all studied traits were significantly different in all genotypes. Titicaca planted on March 6th had the highest Yield (2276 kg.ha-1).The grain Yield and Yield components decreased with the delaying the planting date. Compared to early plantings, Latest date, April 6th, led to reduction of all traits, especially grain Yield (about 50%). The results of simple phenotypic correlation between the studied traits showed that grain Yield per hectare had the highest correlation with plant Yield (0.877) and then with leaf area index (0.832), panicle weight (0.815) and number of branches per plant (0.745) that was significant at the 1% probability level.

مدل SWAP را یک مدل اگروهیدرولوژیکی، زراعی - هیدرولوژیکی و اکوهیدرولوژیکی می نامند. در این تحقیق مدل SWAP در برآورد عملکرد محصول و عملکرد بیولوژیک سویا و درصد رطوبت موجود در خاک طی فصل کشت مورد مطالعه قرار گرفت. در این تحقیق ابتدا مدل SWAP بر اساس نتایج مزرعه ای حاصل از کشت سویا برای چهار سناریوی آبیاری شیاری در سال زراعی 88-1387 تحلیل حساسیت و واسنجی شد. سپس بر اساس نتایج مزرعه ای سال زراعی 89-1388 مورد اعتباریابی قرار گرفت. نتایج این مطالعه نشان داد که این مدل عملکرد دانه را بهتر از عملکرد بیولوژیکی سویا شبیه سازی می کند. همچنین نتایج تحلیل حساسیت مدل نشان داد که مدل SWAP نسبت به داده های ورودی رطوبت باقی مانده و هدایت هیدرولیکی اشباع بسیار حساس است و با کوچکترین تغییر در داده های ورودی خاک شامل ضریب هدایت هیدرولیکی اشباع و رطوبت باقی مانده نتایج خروجی به شدت تغییر می کند. به استناد تحلیل های آماری با وجود متغیر های متعدد ورودی، مدل SWAP مقدار رطوبت خاک، شاخص سطح برگ، کارایی مصرف آب و عملکرد محصول را به خوبی برآورد می کند، زیرا در همه موارد ضریب تبیین بالاتر از 0.8 (به ترتیب برابر 0.86، 0.87، 0.89 و 0.93) و میانگین مربعات خطا کمتر از انحراف معیار داده ها می باشد و آزمون مقایسه میانگین T-test تفاوت معنی دار را بین مقادیر شبیه سازی شده و پیش بینی شده نشان نداد.