Effect of Weeds Control on Crop Growth and Yield in Additive Quinoa (Chenopodium quinoa Willd) and Potato (Solanum tubersum L.) Intercropping

Intercropping system is the growth of two or more crops at the same time, which can lead to decreases in the risk of total crop reduction and increases in yield with control of weeds. Quinoa (Chenopodium quinoa willd.) is a pseudo cereal with high nutritional value which is approximately a new crop in Iran. So, this research was conducted to assess the effects of additive intercropping of quinoa andpotato (Solanum tubersum L.), and the methods of weeds control on yield and yield components of quinoa var. Titicaca in Jiroft and Kahnooj regions.

This study was carried out as split plot based on a randomized complete block design (RCBD) with four replications at Jiroft and Kahnooj regions. Therefore, weeds control treatments including control (no-hoeing), manual weeding (twice within 30 days after planting) and paraquat herbicide (3 days after planting of quinoa) were arranged in the main plots, while additive intercropping patterns at five levels (Q:P in the levels of 5:5, 10:5, 15:5, 20:5 and 30:5 plants per m-2), quinoa sole cropping (30 plants per m-2) and potato sole cropping (5 plants per m-2) were located in sub-plots. The effects of quinoa and potato intercropping on plant height, leaves number per plant, leaf area, flowering time, spike maturity and quinoa harvest time, average of grain weight per plant, grain yield and density of weeds as well as potato tuber yield were measured at both regions. Data were analyzed as combined analysis of variance (ANOVA) using SAS ver. 9.2. Means were compared using the least significant difference (LSD) at the 5% level (P = 0.05).

The results showed that the effects of quinoa and potato intercropping had significant effects on some characteristics of quinoa including leaves number per plant, leaf area, average of grain weight per plant, grain yield of quinoa, tuber yield of potato and density of weeds. However, intercropping had no effect on some characteristics of quinoa such as plant height, flowering time, spike maturity and quinoa harvest time. Based on the results the highest (19 g per plant) and lowest (13.9 g per plant) average of grain weight per plant were obtained in 20:5 and 5:5 plants per m-2 treatments, respectively. Whereas, the highest grain yield (4957 and 4863 kg.ha-1) were obtained in sole quinoa and 30:5 plants per m-2 treatments, respectively. The studied growth characteristics and grain rate per plant in Kahnooj were greater than those in Jiroft. Total land equivalent ratio (LER) index increased with increasing quinoa density in intercropping. The highest total LER was obtained in 30:5 plants per m-2 treatment in Kahnooj region. Moreover, the effect of manual weeding of weeds on the studied properties were more than that of the application of paraquat herbicide. The results also showed that the intercropping of quinoa and potato led to decreases in density of weeds at both flowering and before harvesting times. So that, the lowest density of weeds was related to the intercropping of quinoa and potato with densities of 20:5 and 30:5 plants per m-2 treatments. Whereas the highest rate of density of weeds were related to the sole cropping of quinoa and potato treatments, respectively. Moreover, the results showed that intercropping resulted in greater tuber yield of potato, so that the highest potato tuber yield was obtained in 30:5 treatments.

Based on the results, although the highest average grains per plantwas obtained in the intercropping of 20:5 treatment, the yield of quinoa decreased with the intercropping of quinoa and potato compared with the quinoa sole cropping. Also, the additive intercropping led to decrease in the density of weeds. Although, it seems that for quinoa cropping the climate of Kahnooj is more suitable than Jiroft, the intercropping of potato and quinoa is suitable for Kahnooj and Jiroft regions.