عنوان مقاله [English]
Intercropping is an old cropping practice, possibly as old as the settled agriculture, and is widespread especially in low-input cropping systems. One of the most popular intercropping practices is the cultivation of certain annual legumes with cereals. Intercropping is the production of greater yield on a given piece of land by making more efficient use of the available growth resources using a mixture of crops of different rooting ability, canopy structure, height, and nutrient requirements based on the complementary utilization of growth resources by the component crops. Several indices such as Land Equivalent Ratio (LER), Competitive Ratio (CR) and Aggressivity (A) have been developed to describe the competition and the economic advantage in intercropping. The objective of this study was the evaluation of seed yield and competitive indices in relay intercropping barley (Hordeum vulgare L.) with chickpea (Cicer arietinum L.) under late-season water stress.
Material and Methods
An experiment was carried out as a split-plot based on a randomized complete block design with three replicates at the College of Agriculture and Natural Resources of Darab, Shiraz University during 2017-2018 growing season. The cropping systems included two factors. The main factor was two irrigation regimes including cutting off irrigation at the beginning of the milk development stage and normal irrigation. The subfactor was 8 different combinations of relay intercropping consisted of monoculture of Zehak six-rowed barley cultivar (b), monoculture of Darab chickpea cultivar (c) sole cropping of barley on December and January (b1, b2), sole cropping of chickpea on December and January (c1, c2), and different combinations of relay intercropping consisted of intercropping of barley+ chickpea on December (b1c1), intercropping of barley + chickpea on January (b2c2), intercropping of barley on December +chickpea on January (b1c2), intercropping of barley on January+chickpea on December (b2c1) and cultivation of barley on January+ chickpea on January (b2c2) with a ratio of 1:1. Eventually, seed yield and competitive indices were measured. Competitive indices were including land equivalent ratio (LER), competitive ratio (CR), aggressivity (A) and system productivity index (SPI). Analysis of variance (ANOVA) was performed using SAS v. 9.4 software and the means compared by LSD test at 5% probability level.
Results and Discussion
The results showed that the late-season low water stress had a significant effect on all studied traits and the highest and lowest percentage reduction of grain yield was obtained in chickpea mono-cropping in December (80%) and January (16.1%), respectively. Low water stress increased by 58% and 25% LER of chickpea and total compared to the normal irrigation conditions, respectively. Under low water stress and normal irrigation conditions, barley was dominant species and at low water stress condition competitive power of legumes increased. Also, under low water stress conditions, barley on December+chickpea in January treatment showed the highest CR (0.68) compared to other treatments. In this experiment aggressivity of barley plant was higher in all cropping patterns than chickpea. Finally, SPI was positive in all intercropping treatments.
The result of the present study showed that the highest LER and SPI were obtained in intercropping of barley in December + chickpea in January under low water stress conditions. It can be concluded that intercropping treatments were superior to mono-cropping treatments especially in intercropping of barley in December+ chickpea in January when plants exposed to water stress. Overall, relay intercropping of chickpea in January with barley in December is the best and useful option in grain yield improvement and can be applied by farmers in semi-arid areas such as south regions of Iran.