Effect of intercropping rates of cumin (Cuminum cyminum L.) and Persian shallot (Allium altissimum Regel.) on their growth indices

Cumin (Cuminum cyminum L.) is a small annual herbaceous and annual medicinal plant that is a member of the aromatic plant family (Apiaceae). It is planted in arid and semi-arid regions of Iran. The seeds are used to add flavor to spicy dishes. Cumin seeds contain numerous phytochemicals that are known to have antioxidant, carminative and anti-flatulent properties. In addition, the seeds yield about 22% fats, numerous free amino acids, and a variety of flavonoid glycosides. Persian shallot (Allium altissimum Regel.) is a medicinal, industrial and perennial plant that belongs to the Alliaceae family and has underground bulbs. It is native and endemic of Iran and grows wild on the mountains quite resistant to cold and freezing stress. Persian shallot is widely used in food and medicinal industries. Intercropping allows for improved resource use efficiency such as light, water and nutrients and beneficial interactions between the plants. Intercropping work to decrease the spread of plant diseases by reducing the quantity of susceptible host plants. Other benefits of intercropping include optimal use of resources, stabilization of yield, weed suppression, improved soil fertility conservation, and higher economic returns. The paper evaluated the effect of intercropping ratios as replacement series of cumin and Persian shallot on growth physiological indices such as dry matter (DM), leaf area index (LAI), crop growth rate (CGR) and relative growth rate (RGR).          

This experiment was conducted based on a randomized complete block design with three replications at the Agricultural Research Station, College of Agriculture, Ferdowsi University of Mashhad during growing season of 2014-2015. Replacement intercropping ratios such as 80% cumin+20% shallot, 60% cumin+40% shallot, 50% cumin+50% shallot, 40% cumin+60% shallot, 20% cumin+80% shallot and their monoculture were considered as treatments. Plant density for shallot bulbs and cumin seeds were considered as 10 bulbs.m-2 and 120 plants.m-2, respectively. DM, LAI, CGR and RGR were measured and calculated were measured and calculated. In order to measure the growth indices, the destructive samplings were carried out every 10 days from 50 cm of row in each plot. All plants were harvested by cutting at the soil surface. Plants were then divided into leaf and stem. The areas of green leaves were measured using a Delta-T leaf area meter (Delta-T Devices, Cambridge, England). Then the samples including stems and leaves were dried in a forced-air oven at 70 ০C for 48 h and after witch DM was measured. The leaf area data was divided to ground area and the leaf area index (LAI) was obtained. The LAI data was fitted to the equation to predict the LAI in growth season. The sigmoid equation was fitted to the TDM data and by derivation from this equation, CGR and RGR were obtained. The graphs were drawn by Excel.

The results showed that the maximum and the minimum DM of cumin and Persian shallot were observed in their monoculture with 426 and 289 g.m-2, respectively. Crop growth rate of cumin reached to its peak in 50 days after planting followed by a decreasing trend afterwards, the highest and the lowest CGR were recorded in monoculture (8.45 g.m-2.d-1) and 20% cumin+80% Persian shallot (13.7 g.m-2.d-1), respectively. For Persian shallot, the time was calculated with 55 days after emergence. The maximum and the minimum CGR of Persian shallot were calculated for its monoculture (8.0 g.m-2.d-1) and 80% cumin+20% Persian shallot, respectively. RGR in all intercropped treatments declined as plant age increased, so that at the end of growth season RGR got close to zero. At the beginning of growth stage, due to radiation penetration and less shading and less respiration, RGR is more and its reduction slope is less.

The results indicated that the intercropping of cumin with Persian shallot increased growth physiological indices such as LAI, DM, CGR and RGR. Studied traits of cumin and Persian shallot were increased by changing in planting ratios from intercropping to its monoculture. The results confirmed the better use of resources especially for radiation and water of these plants in intercropping treatments.