بررسي جنبه هاي اكوفيزيولوژيك و شاخص هاي كيفيت علوفه در كشت مخلوط ذرت (Zea mays L) و لوبيا چشم بلبلي (Vigna unguiculata L)

Evaluation of the Ecophysiological Aspects and Forage Quality Indices in the Intercropping of Maize (Zea mays L.) and Cowpea (Vigna unguiculata L

به منظور بررسي جنبه هاي اكوفيزيولوژيك و كيفيت علوفه كشت مخلوط ذرت (Zea mays L) و لوبيا چشم بلبلي (Vigna unguiculata (L.) Walp)، آزمايشي در قالب طرح بلوكهاي كامل تصادفي با شش تيمار و سه تكرار در پژوهشكده كشاورزي دانشگاه زابل، در سال زراعي 94-1393 انجام شد. تيمارها شامل؛كاشت خالص ذرت، 100% ذرت + 15% لوبيا، 100% ذرت + 30% لوبيا، 100% ذرت + 45% لوبيا، 100% ذرت + 60% لوبيا و كشت خالص لوبيا چشم بلبلي بود. نتايج نشان داد كه جذب نور، رطوبت خاك و دماي خاك سيستمهاي كاشت در سطح احتمال پنج درصد معني دار بود. كشتهاي مخلوط، ميزان تابش جذب شده و رطوبت بيشتري را در طول فصل رشد كسب نمودند و دماي كمتري نيز نسبت به تك كشتي خود داشتند. همچنين نتايج نشان داد، شاخصهاي كيفي علوفه، غلظت پروتئين خام (CP) و ميزان خاكستر ذرت در كشت مخلوط لوبيا چشم بلبلي افزايش يافت و غلظت ديواره سلولي (NDF)، فيبرهاي نامحلول در شوينده هاي اسيدي (ADF) ذرت كاهش يافت، به نحوي كه بيشترين ميزان پروتئين خام ( 9/41 درصد)، خاكستر (12/16 درصد) و قابليت هضم ماده خشك ذرت (72/77 درصد) از نسبت كاشت 100% ذرت+ 60% لوبيا چشم بلبلي و بيشترين ميزان NDF (46/66 درصد)، ADF (26/66 درصد) از كشت خالص ذرت به دست آمد. به دليل همبستگي منفي بين ADFو قابليت هضم ماده خشك (DMD) با كاهش يافتن غلظت ADF قابليت هضم علوفه افزايش پيدا كرد. بيشترين عملكرد علوفه خشك از كشت مخلوط 100% ذرت + 60% لوبيا ( t.h-114/61) در حالي كه كمترين عملكرد از كشت خالص لوبيا ( t.ha-1 0/93) به دست آمد. به طور كلي،كشت مخلوط به لحاظ توليد كمي و كيفي علوفه نسبت به كشت هاي خالص برتري نشان داد.

Introduction Intercropping is a crop management system involving two or more crop species grown together for at least portion of their respective productive cycle and planted sufficiently close to each other so that inter specific competitions occurs. The reason of yield advantage of intercropping are mainly that environmental resources such as water, light and nutrients can be utilized more efficiently in intercropping than in the respective sole cropping systems. Intercropping system is one the efficient crop production managements with minimum adverse effects on the environment, using the principles of ecological agriculture. Materials and Methods In order to study the ecophysiological aspects and forage quality intercropping maize (Zea mays L.) and cowpea (Vigna unguiculata L.), an experiment was conducted based on a randomized complete block design (RCBD) with three replications at the Research Farm, University of Zabol in 2015. The experimental treatments were: sole cropping of maize, 100% maize + 15% cowpea, 100% maize + 30% cowpea, 100% maize + 45% cowpea, 100% maize + 60% cowpea and sole cropping of cowpea. Each plot consisted of five rows planting, with a distance of 60 cm length was formed five meters. Maize and cowpea seeds were simultaneously sown. Photosynthesis active radiation (PAR) was measured between 12-13 hours on occasions. Mean values for each plot were then used to calculate the percentage of PAR interception by plant canopy as follows: %PARi = [1- (PARb / PARa)] × 100 Where the subscript i designates intercepted PAR, a and b subscripts designate PAR above and below the plant canopy, respectively. Corn in the dough stage of grain and cowpea were at physiological maturity stage, harvest was carried out simultaneously. Samples dried at 70°C for 48 h and weighed. The crude protein content was calculated by multiplying the Kjeldahl nitrogen concentration by 6.25. ADF (acid detergent fiber) and NDF (neutral detergent fiber) concentrations were measured. Digestible dry matter (DDM) were estimated. DDM = 88.9-(0.779 x ADF % dry matter basis) Intercropping advantage and competition between maize and cowpea in intercrops were calculated LER was used to quantify the efficiency of the intercropping treatments: LER = Ymm/ Ybb + Ymb/ Ycc where Ymm and Ycc are yields of pure stands of maize and cowpea, Ymc and Ycm are yields of maize and cowpea in the intercropping system, respectively (Willey, 1979). Statistical computations using SAS software and comparison of means were tested by LSD at P<0.05 level. Results and Discussion Physiological and morphological differences between intercrop components affect their ability of using environmental resources, light interception and water. The results showed that intercropping systems had a significant effect on environmental resources consumption, where intercropping systems had more light interception and water compared to sole crops. Maximum absorption of photosynthesis active radiation in the canopy cropping system 100% maize + 60% cowpea and the cropping systems also mixed, soil temperature was lower compared to sole cropping. Crude protein concentration and maize ash mixed with cowpea increased, cell wall concentrations and acid detergent fiber (ADF) maize reduced. The highest protein content (%9.41), dry matter digestibility (72.77), and ash (12.16) obtained in mixed 100% maize + 60% cowpea. The highest neutral detergent fiber (46.66%) and ADF (26.66%) obtained from sole cropping maize. Due to the negative correlation between the ADF and DMD, ADF Reducecaused increase DMD. The highest dry matter yield of treatment 100% maize + 60% cowpea With (14.61 t ha-1), while the least yield obtained from the culturing of cowpea (0.93 t.ha-1). Intercropping systems showed superiority over pure cultures in terms of qualitative and quantitative production of forage. Conclusion The results of this study showed that the total yield of forage can be improved by adding cowpea ratios to the maize pure stand. The calculated LER exceeded unity the intercrops, showed that resources such as water, light and nutrients utilized more efficiently in intercropping than in the respective sole cropping systems. Based on the overall results of the experiment considering total forage yield and quality, 100M+60 C intercrop could be suggested farmers to produce acceptable higher amount of forage in quality than sole cropping of maize.