Evaluation of Competitive Indices and Grain Yield of Triticale (× Triticosecale Wittmack) – Chickpea (Cicer arietinum L.) Intercropping as Affected by Bio-Organic Fertilizer and Water Stress

Todays, efforts to increase crop yields have led to the indiscriminate use of chemical fertilizers, especially nitrogen (N) and phosphorus (P) fertilizers. It has caused soil and groundwater pollution and the destruction of soil microbial communities. Therefore, researchers should look for ways to replace N fertilizers and reduce their side effects. Intercropping of cereals and legumes due to differences in the distribution and depth of roots in the soil profile can reduce competition for water and the survival of these plants in water shortage conditions. Among the methods that may reduce the use of N and P fertilizers and thus reduce sensitivity to water stress is the intercropping of cereals and legumes. Using growth-promoting N-fixing bacteria such as Azospirillum brasilense and phosphorus solvents such as Pseudomonas fluorescens as biofertilizers can be another way to reduce the use of N and P fertilizers and the adverse effects of water stress. Therefore, the aim of this study was to investigate the effects of different fertilizer systems [chemical, integrated, and biological] on yield and competitive indices in triticale (× Triticosecale Wittmack) - chickpea (Cicer arietinum L.) intercropping under water stress conditions in Southern Iran (Fars province).

This experiment was performed as a split factorial on a randomized complete block design with three replications in the research farm of the Darab Faculty of Agriculture and Natural Resources-Shiraz University in the 2019-2020 growing season. Experimental treatments included two levels of irrigation (Ir) [Normal: irrigation based on plant water requirement (IRN) and water stress: irrigation based on plant water requirement up to the milking stage (WS)] as the main factors. The Sub-factors included three sources of fertilizer (F) [Chemical: 50 kg P.ha-1 +150 kg N.ha-1, Bio-organic: 40 tons of manure sheep ha-1 + inoculation with Pseudomonas fluorescens and Azospirillum brasillens, Integrated: 25 kg P ha-1 + 75 kg N.ha-1 + 20 tons of manure sheep ha-1 + inoculation with Pseudomonas fluorescens and Azospirillum brasilens] and three types of cropping systems (Cp) [Monoculture of triticale, monoculture of chickpea, and intercropping of triticale-chickpea (1:1)]. The crops Grain yield were measured, of the crops was measured and competitive indices including land equivalent ratio (LER), aggressivity (A), competitive ratio (CR), and system productivity index (SPI) were computed. The SAS 9.1 software was used to analyze the data, and the means were separated using the least significant difference (LSD) test at a 5% probability level.

 The results showed that the cessation of irrigation after the milking stage put severe stress on the triticale and chickpea during the grain filling period and reduced grain yield of both plants. The Ir × F interaction for triticale and chickpea grain yield showed that the lowest reduction of their grain yield (31% and 27%, respectively) were obtained in Bio treatment due to water stress as compared to IRN. Furthermore, The Ir × Cp interaction for triticale and chickpea grain yield showed that the water stress reduced their grain yield. However, the reductions were lower in intercropping system of triticale (38%) and chickpea (24%) as compared with their sole cropping. Late season water stress increased triticale, chickpea and total LER as compared with IRN conditions by 40, 65 and 51%, respectively. Furthermore, the Ir × F interaction showed that the highest and the lowest reductions (55% and 17%, respectively) of SPI were achieved in chemical and Bio treatments as a consequence of water stress conditions. 

 Based on the results obtained from this study, it can be concluded that the intercropping system of triticale and chickpea is superior to their monocropping under late season water stress conditions. Also, the lowest reduction of chickpea and triticale grain yields as a consequence of water stress was obtained by the application of Bio and integrated fertilizers. Therefore, the use of Azospirillum brasiliens and Pseudomonas fluorescens with sheep manure fertilizer not only mitigates the negative effects of water stress, but also reduces the excessive use of N-P chemical fertilizers and their harmful environmental effects and it can be an effective step for sustainability of agricultural systems.