چكيده لاتين :
Introduction
Intercropping is a sustainable practice used in many developed and developing countries and an essential element of agricultural sustainability. Intercropping by decreasing the inputs through reduced fertilizer and pesticide requirements, minimizes the negative environmental impacts of agriculture (Lithourgidis et al., 2011). It is known that legumes are beneficial to the soil by improving nutrient availability and structure, reducing pest and disease incidence and hormonal effects (Lithourgidis et al., 2011). Biological nitrogen fixation, deriving from the symbiosis of leguminous plants and rhizobium bacteria, is the major benefit of legumes (Launay et al., 2009). The main advantage of intercropping is the more efficient utilization of the available resources and the increased productivity compared to monocropping (Launay et al., 2009). For example, intercropping of maize and bean increased light interception and improved soil moisture conditions compared to monoculture. Intercropping of ajowan and fenugreek improved the efficiency of cropping systems. Intercropping of bean (Phaseolus vulgaris L.) and sweet basil (Ocimum basilicum L.) had a significant effect on light efficiency and biological yield.
The main goal of this study was to introduce suitable sowing patterns on two medicinal plants production with respect to legume and medicinal plant intercropping such as dill (Anethum graveolens L.) and fenugreek (Trigonella foenum-graecum L.) based on replacement series.
Materials and methods
A field study was conducted to evaluate radiation absorption and use efficiency in fenugreek and dill in row intercropping as replacement series at Agricultural Research Station of Ferdowsi University during growing season of 2013-2014. Treatments included 20% fenugreek+ 80% dill, 40% fenugreek+ 60% dill, 60% fenugreek+ 40% dill, 80% fenugreek+ 20% dill and their monoculture. As summarized by Sinclair and Gardner (1998), potential crop growth and yield are the result of four processes. First, the radiation interception by crop canopies provides the required energy for crop production. Second, the efficiency of conversion of the intercepted radiation to plant mass which determines the amount of produced dry matter. Third, the time required for plant mass accumulation that determines the total amount of accumulated plant mass. Fourth, the fraction of the accumulated plant mass allocated to the harvestable part that influences crop productivity.
For statistical analysis, analysis of variance (ANOVA) and Duncan’s multiple range test (DMRT) were performed using SAS version 9.3 (SAS Institute Inc., Cary, NC, USA).
Total above-ground dry matter (g.m-2), TDM, during vegetative stages (i = 1, 2, .., k _ 1, k) was calculated as:
Where RUE is radiation use efficiency (g.MJ-1 PAR), F is the fraction of radiation intercepted, PAR is photosynthetically active radiation (MJ.m-2.day-1), and i is the number of days after emergence (k is the day of flowering). RUE for a vegetative stage was defined as the ratio of TDM to intercepted PAR (g.MJ-1 PAR).
With regard to potential crop yield, assuming that TDM reaches a maximum value on the k-th day, TDM during the reproductive stages (i = k + 1, k + 2, ..., n _ 1, n) was given by the following relationship:
Where Y is harvestable yield (g m-2) and n is the day of maturity. Therefore, as RUE was defined for the reproductive stage as the ratio of Y to intercepted PAR, Y (i.e., maize ears and bean pods) was given by:
Grain yield (i.e., maize kernels and bean seeds) was estimated using the ratio of grain dry mass to Y. In this study, the measured ratio during the 1998/1999 growing season was used (0.69 for maize and 0.72 for beans) (Tsubo, 2000).
Results and Discussion
Results indicated that leaf area index, light absorption, total dry matter accumulation and radiation use efficiency (RUE) of fenugreek and dill increased in all intercropping ratios compared to monoculture. Dry matter production was linearly related to the amount of intercepted PAR. The value of RUE changed over time, partially as a consequence of changes in canopy photosynthetic rates. RUE range for fenugreek was from 0.65 g MJ-1 in monoculture to 0.9 g MJ-1 in 40% fenugreek + 60% dill. RUE range for dill was from 0.35 g MJ-1 in its monoculture to 0.72 g MJ-1 in 40% fenugreek+ 60% dill. However, the response of canopy photosynthesis to radiation was complex and depended on incident radiation flux density and individual leaf photosynthetic response. Radiation-use efficiency may be affected by changes of these variables as PAI increased.
Conclusion
Dry matter production was linearly related to the amount of PAR intercepted. RUE changed partially as a consequence of changes in canopy photosynthetic rates. However, the response of canopy photosynthesis to radiation was complex and depended on incident radiation flux density and individual leaf photosynthetic response. According to the results, intercropping of plants of 40% fenugreek + 60% dill can be beneficial in term of ecological management.
Keywords: Leaf area index, Radiation absorption, Row intercropping, Total dry matter
References
Launay, M., Brisson, N., Satger, S., Hauggaard-Nielsen, H., Corre-Hellou, G., Kasynova, E., Ruske, R., Jensen, E.S., and Gooding, M.J. 2009. Exploring options for managing strategies for pea-barley intercropping using a modeling approach. European Journal of Agronomy 31: 85-98.
Lithourgidis, A.S., Dordas, C.A., Damalas, C.A., and Vlachostergios, D.N. 2011. Annual intercrops: an alternative pathway for sustainable agriculture. Australian Journal of Crop Science 5: 396-410.
Tsubo, M., Walker, S., 2002. A model of radiation interception and use by a maize–bean intercrop canopy. Agriculture, Forest and Meteorology 110: 203-215.
