اثر تراكم بوته و ميزان مصرف كود دامي بر شاخص هاي رشدي ارقام لوبياي قرمز (Phaseolus vulgaris L.) در شرايط آب و هوايي مشهد

Effects of Plant Density and Cow Manure Levels on Growth Criteria of Bean (Phaseolus vulgaris L.) Cultivars under Mashhad Climatic Conditions

به منظور ارزيابي روند تغييرات شاخص هاي فيزيولوژيك رشدي ارقام لوبيا (Phaseolus vulgaris L.) تحت تاثير تراكم هاي مختلف بوته و مقادير كود دامي، آزمايشي به صورت فاكتوريل در قالب طرح بلوك هاي كامل تصادفي با 36 تيمار و سه تكرار در مزرعه تحقيقاتي دانشكده كشاورزي دانشگاه فردوسي مشهد در سال زراعي 94-1393 انجام شد. فاكتور‏هاي مورد مطالعه شامل چهار رقم لوبياي قرمز (اختر، لاين 81083-D، ناز و گلي)، سه تراكم بوته (13/13، 20 و 40 بوته در مترمربع) و سه سطح كود گاوي كاملاً پوسيده (صفر، 15 و 30 تن در هكتار) بود. شاخص هاي رشدي مورد بررسي شامل شاخص سطح برگ، ميزان تجمع ماده خشك، سرعت رشد محصول و سرعت رشد نسبي ارقام لوبيا قرمز در سطوح مختلف تراكم و كود دامي بود. نتايج نشان داد كه بيشترين تجمع ماده خشك با 4/315 گرم در مترمربع براي رقم گلي و كمترين مقدار آن با 5/214 گرم در مترمربع در رقم اختر مشاهده شد. بالاترين شاخص سطح برگ (59/2) با مصرف 30 تن در هكتار كود دامي در رقم گلي به دست آمد. در هر چهار رقم حداكثر سرعت رشد محصول در 42 روز پس از سبز شدن و در تراكم 40 بوته در مترمربع حاصل شد و با كاهش تراكم به 13/13 بوته در مترمربع سرعت رشد محصول 18 درصد كاهش يافت. همچنين در تراكم 40 بوته در مترمربع بالاترين سرعت رشد نسبي نيز مشاهده شد.

Introduction In common bean (Phaseolus vulgaris L.), plant density can affect canopy architecture, light conversion efficiency, duration of vegetative growth, dry matter production, seed yield and ultimately, the economic productivity of a crop. Therefore, optimizing plant density, which may be defined by both the number of plants per unit area and the arrangement of plants on the ground, is a pre-requisite for obtaining higher productivity of common bean. Therefore, varying plant density may be a viable alternative to manipulate the productivity of bean under different environmental conditions through their changes in physiological processes. Moeinit et al. (2009) reported the increase in common bean seed yield with the increase in plant density. Another important factor determining growth indices is manure. Integrated supply of nutrient to plants through planned combinations of organic and inorganic sources is becoming an increasingly important aspect of environmentally sound agriculture. Materials and methods In order to study the effects of plant density and cow manure levels on four common bean cultivars an experiment was conducted as a factorial arrangement based on complete randomized block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during two growing seasons of 2011-2012 and 2013-2014. The experimental treatments were plant density in three levels (13.13, 20 and 40 plants.m-2), three cow manure levels (0, 15 and 30 kg.ha-1) and four common bean cultivars (Gholi, Akhtar, Naz and D-81083). All common bean plants were harvested by cutting at the soil surface. Dry matter (DM), leaf area index (LAI), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR) were measured and calculated accordingly. Plants were then divided into leaf and stem. The areas of green leaves were measured using a Delta-T leaf area meter. The leaf area data was divided to ground area and the LAI was obtained. The LAI data was fitted to the Gaussian equation to predict the LAI of common bean in growth season. The sigmoid equation was fitted to the TDM data and by derivation from this equation, the CGR and RGR were obtained (Steinmaus and Norris, 2002). The regression analysis was performed by SAS 9.1 and the graphs were prepared by Excel. Results and discussion The results showed that during the days after planting in all treatments, LAI first increased until 56 days after planting and then it had a descending trend. The highest slope of leaf area increase is related to plant density (40 plants.m-2). Although, decreasing plant density from 40 plants.m-2 to 13.13 decreased LAI 29%. The maximum of LAI was obtained in cow manure (30 t.ha-1) (2.57). Goli with 2.61 had the greatest LAI. CGR first increased slightly and then increased more quickly until 56 days after planting, then decreased with a sharp slope. The lowest RGR was belonged to 13.13 plant.m-2 density, 0 t.ha-1cow manure and Akhtar cultivar) (with 8.32 g.m-2.day, 7.90 g.m-2.day and 4.26 g.m-2.day, respectively). RGR decreased as the plant age increased so that at the end of growth season RGR was close to zero. At the beginning of growth stage, due to more penetration of light into the canopy and less shadow of the leaves on each other and the less respiration, RGR is more and its reduction slope is less. Plant density with 40 plants.m-2 shows the highest primary RGR and the plant density with 3.13 plants.m-2 shows the lowest one. The highest RGR in the 56th day has been related to 30 t.ha-1cow manure. Conclusion We can conclude that indeterminate common bean cultivars such as Goli and Naz showed the greatest growth rate and these findings indicate that the common bean crop has the ability to alter plant size and canopy structure in response to changes in plant density. These strategies can be used as cultural methods to reduce the competitive ability of weeds and maintain common bean growth at acceptable levels. However, there is a need to evaluate numerous common bean cultivars in different locations and years to find cultivars with high competitive ability and stability in yield. Acknowledgments The authors acknowledge the financial support of the project by Vice President for Research and Technology, Ferdowsi University of Mashhad, Iran.