Reaction of chickpea grain yield and its components in triticale-chickpea intercropping to chemical and bio fertilizers under water stress conditions

Water stress and nitrogen (N) excess or defficiency are the major problems and the main cause of yield and yield components reduction as compared to other non-biological stresses (Barati & Bijanzadeh, 2020) in crop productions of arid areas. Organic farming is proposed as a solution for above problems. This farming system reduce using of chemical inputs and irrigation water use. The utilization of free aerobic bacteria, such as Azospirillum brasilense, in organic farming practices offers the potential to reduce the need for nitrogen fertilizer by harnessing the ability of these bacteria to stabilize atmospheric nitrogen (N2). Similarly, the application of Pseudomonas fluorescens can enhance the availability of soluble phosphorus in the soil, benefiting plant growth and nutrient uptake. In addition, intercropping is recommended as a strategy to enhance biodiversity in organic farming systems. This approach can alleviate water and nutrient stresses by reducing competition among plants for these resources in the soil. However, there is a lack of information regarding the interaction between organic fertilizer and the triticale-chickpea intercropping system in mitigating the detrimental effects of water stress on chickpea. To address this knowledge gap, the present study was conducted in the arid region of Darab, located in the Fars province of southern Iran. Therefore, this study was aimed to investigate the interaction effect of different fertilizer systems (chemical, Integrated and biological) and different irrigation regimes on the yield and yield components of chickpea in sole and intercropping of chickpea-triticale, in an arid area of southern Iran (Fars province - Darab).

This experiment was performed as a split factorial on a randomized complete block design with three replications in the research farm of Darab Faculty of Agriculture and Natural Resources - Shiraz University in the 2019-2020 growing season. Experimental treatments included two levels of irrigation (Ir) [Normal (IRN): irrigation based on the plant water requirement and water stress (WS): irrigation based on the plant water requirement up to the flowering stage] as the main factor. Sub-factors included three sources of fertilizer system (Fs) [Chemical: 50 kg P ha-1 +150 kg N ha-1, Integrated: 25 kg P ha-1 + 75 kg N ha-1 + 20 tons manure sheep ha-1 + inoculation with Pseudomonas fluorescens and Azospirillum brasilens, Bio: 40 tons manure sheep ha-1 + inoculation with Pseudomonas fluorescens and Azospirillum brasillens] and two types of cropping system (Cs) [monoculture of chickpea and intercropping of triticale-chickpea (1:1)]. Grain yield and its components of chickpea was measured and harvest index (%) were calculated. Data were analyzed using SAS 9.1 software and the means were separated by least significant difference (LSD) test at 5% probability level.

The Ir × Fs interaction showed that the water stress significantly reduced grain yield of chickpea. However, it’s the highest and lowest reduction was obtained in the chemical and bio fertilizer treatments by 68% and 27%, respectively. In a similar study, the lowest reduction in chickpea yield under water stress compared to normal irrigation was obtained in bio fertilizer treatment (Khalegh nezhad & Jabari, 2015). The Ir × Cs interaction also showed significant effect on the grain yield. The impact of water stress on grain yield varied depending on the cropping system, with the highest reduction observed in monocropped chickpea (55%) and the lowest reduction in intercropped chickpea (24%). This interaction also revealed that both intercropped and sole chickpea experienced decreases in yield and yield components under water stress, but the severity of the reduction was greater in sole cropping. Analysis of chickpea yield components, such as the number of pods per plant, biomass yield, and harvest index, showed similar trends as observed in grain yield under the Ir × Cs interaction. The Ir × Fs interaction had differing effects on the number of seeds per pod and seed weight, with water stress leading to a decrease in these traits. Similar to the behavior of grain yield, the least reduction in these traits under water stress was observed in the Bio and integrated fertilizer systems. Water stress increased the LER of pea and total LER by 65% ​​and 51%, respectively, as compared to the IRN conditions.

The results of this study showed that the water stress after flowering stage of chickpea led to a decrease in grain yield and its components that have been formed at this stage. If farmers intend to cut off irrigation after the flowering stage in chickpea due to the lack of water resources, it is suggested to use of chickpea-triticale intercropping system and the bio or integrated fertilizers that are as environmentally friendly alternatives to chemical fertilizers for increasing chickpea grain yield.