v. barati

South of Iran has been located in the dry belt and desert strip thus water stress has always been one of the serious problems in its agriculture (Buzarjomehri et al., 2020). Intercropping is the cultivation of two or more plant species in a specific land and growing season, which is important in agricultural systems with limited resources and low input (Brooker et al., 2015). Due to the differences in the rooting depth, lateral expansion, and root density of cereals and legumes, they have been the best candidates for intercropping traditionally for limited soil water and nutrient availability environments (Babalola, 1980; Haynes, 1980). Application of bio-fertilizers (PGPR bacteria) that have nitrogen (N) fixation and phosphorus (P) solubilizing activity (Azospirillum brasilense and Pseudomonas fluorescence, respectively) is a promising approach for obtaining N, P, and water-restricted areas (Tien et al, 1979; Barea, 2015). Organic manures enhance soil water holding capacity and serve as excellent slow-release sources of nitrogen (N) and phosphorus (P) in the soil (Risse et al., 2006). This study aimed to investigate the effect of different fertilizer systems (chemical, integrated, and bio-organic) on triticale grain yield and its components in sole and intercropped triticale in triticale/chickpea system under late season water stress in a hot and dry area of southern Iran (Fars province - Darab).

To evaluate the yield and yield components of triticale (× Triticosecale Wittmack) in monoculture and intercropping with chickpea (Cicer arietinum L.) under late season water stress conditions, a split-factorial experiment in a randomized complete block design with three replications was implemented at the research field of the College of Agriculture and Natural Resources of Darab - Shiraz University in 2019-2020 growing season. Treatments were two levels of irrigation (Ir): [1- normal (IRN): irrigation based on the plant water requirement up to the physiological maturity stage (ZGS92) and 2- water stress (WS): irrigation based on the plant water requirement up to the milking stage] as the main plots and three fertilizer sources (FS) [1- chemical: ( 50 kg P ha-1 + 150 kg N ha-1), 2- integrated: (25 kg P ha-1 + 75 kg N ha-1 + 20 tons sheep manure ha-1 + inoculation with Pseudomonas fluorescens and Azospirillum brasilense) 3- bio-organic: 40 tons sheep manure ha-1 + inoculation with Pseudomonas fluorescens and Azospirillum brasilense] and two cropping systems (Cs) [1- monoculture of triticale, 2- intercropped triticale with chickpea (1:1)] as the sub-plots. Triticale grain yield and its components were measured and the harvest index (%) was calculated. Data were analyzed using SAS 9.1 software and the means were separated by the least significant difference (LSD) test at 5% probability level.

The results demonstrated that water stress reduced the grain yield and its components in triticale, with the extent of reduction varying among different treatments. In the Ir × Cs interaction, the Ws treatment reduced the triticale grain yield as compared to IRN by 38% and 55 % in the intercropped and sole-triticale, respectively. The Ir × Fs interaction showed that the grain yield decreased by water stress as a function of the fertilizer system (60.4%, 43.7%, and 30.7% reduction in the chemical, integrated, and bio-organic treatments, respectively). Evaluation of the results related to the triticale yield components (grain weight, biological yield, and harvest index) also showed that the Ws treatment reduced these traits. However, the least reduction occurred in bio-organic fertilizer as compared with the other fertilizer systems (significant Ir × Fs interaction). Furthermore, the Ir × Cs interaction showed that the Ws treatment reduced triticale grain weight and its biological yield as compared to IRN in both cropping systems with different manners. The least reduction of their traits by Ws treatment was showed in intercropped triticale as compared to its sole cropping.

Based on the results of this study, intercropped triticale with chickpea and using of bio-organic fertilizer were recommended for hot and dry areas of southern Iran where water stress may occur at the end of the growing seasons. Using these strategies leads to water stress alleviation and therefore less reduction of triticale grain yield in these environments.

In the dry climate of southern Iran including Fars province, most precipitation occurs in winter, thus winter cereals such as triticale (Triticosecale Wittmack) experience water shortage at booting, flowering and grain filling stages in spring. The booting, flowering and grain filling periods are the most sensitive stages to water deficit. Nitrogen fertilizer application is a farmer’s common practice to increase yield, but its performance depends mainly on soil water status than the amount and timing of N applications. On the other hand, matching N fertilization with crop water availability is essential for achieving acceptable grain yield. Farmers of southern Iran use N fertilizer beyond the recommended rate. High N fertilizer application in dry areas that water availability limitations frequently occurred during the grain filling stage of cereals increased severity of water stress. Some authors reported that the silicon application reduces the destructive effects of drought stress by physiological, biochemical, and physical mechanisms (Hattori et al., 2005). Therefore, silicon foliar application may decrease water stress severity, especially in high N crops. Therefore, the aims of this study were to investigate the effects of silicon foliar application, different N rates and irrigation regimes on triticale yield in an arid area of southern Iran (Fars province).     

This research was conducted at the experimental farm of the Darab Agricultural Faculty of Shiraz University. A split factorial experiment in a randomized complete block design with three replications was carried out in the 2017-2018 growing season. Treatments included two levels of irrigation as the main plots [normal irrigation; irrigation based on the plant's water requirement up to the physiological maturity (IRN) and deficit irrigation; irrigation based on the plant's water requirement up to the anthesis stage (cutting of irrigation after anthesis) (IRDI)]. Also, sub plots were two levels of silicon foliar application [0, and 3 mM] and three N fertilizer levels [N0, no nitrogen fertilizer (control); N100, 100 kg N ha-1; N150, 150 kg N ha-1]. Biological yield, grain yield, yield components, plant height, spike length and chlorophyll index of flag leaf were measured. Then, the harvest index (HI) was calculated. Data were analyzed by using SAS 9.1 software (SAS Institute, 2004) and the means were compared using Duncan’s multiple range test at 5% probability level.

The results showed that the IRDI could cause severe water stress in the grain-filling period of the triticale life cycle and consequently reduction of 1000-grain weight, number of grains per spike and number of fertile tillers per m2. However, this reduction was more severe for 1000- grain weight than the other grain yield components and was not constant in different N fertilizer levels (18%, 21% and 36% reduction for N0, N100 and N150 kg N ha-1). Foliar silicon application decreased severity of late-season water stress and consequently improved 1000-seed weight, chlorophyll index, biological yield and finally HI and grain yield. With respect to grain yield, under IRN conditions, the highest grain yield was achieved by N150. Water stress decreased grain yield as a function of N fertilizer (24%, 26% and 46% reduction for N0, N100 and N150 kg N ha-1). Therefore, application of N100 could be acceptable for IRDI conditions.

According to the results of this study, the highest triticale grain yield (7098 kg ha-1) achieved by N150 in normal irrigation. The IRDI significantly decreased triticale grain yield at all N levels as compared with IRN. However, this reduction was different in N fertilizer rates (24%, 26% and 46% reduction for N0, N100 and N150). Therefore, the highest grain yield under IRDI conditions (4128 kg ha-1) was observed in N100. Therefore, with respect to environmental and economical considerations application of 100 and 150 kg N ha-1 were recommended for late-season water stress and normal irrigation conditions, respectively. Silicon foliar application decreased the severity of water stress and consequently increased grain yield (26%) under IRDI conditions. Therefore, the application of 3 mM of silicon at the anthesis stage is recommended for farms of triticale that expose to late-season water stress in southern Iran (Fars province).

To identify the important features of triticale that contribute to improving grain and biomass Water Use Efficiency (WUEg and WUEb, respectively), grain yield, and Nitrogen (N) remobilization, a 2-year side-by-side experiment was carried out on triticale with different nitrogen sources and water regimes, in a typical Mediterranean environment of Iran. There were two levels of water regimes: Normal Irrigation (IRN) and irrigation cut off after anthesis stage (IRMD). Rain-fed treatment (IR0) was included in the second year. Four N sources including Azospirillum brasilense (Bio), Azospirillum brasilense+75 kg N ha-1 as urea (Bio+N75), 150 kg N ha-1 as urea (N150), and control unfertilized (N0) plots were used. This study showed that the highest grain yield (6,258 kg ha-1) was achieved by chemical N fertilizer application (N150) under IRN. In contrast, the application of Bio+N75 resulted in the highest grain yield as compared with the other N sources under IRMD (4,409 kg ha-1) and IR0 (2,960 kg ha-1) conditions. Water stress significantly increased WUEb at all N sources. However, WUEg slightly increased by IRMD and then sharply decreased by IR0 in all N sources, except N150 plots, where WUEg drastically decreased by water stress imposed by IRMD and IR0. The Bio+N75 treatment had the highest N remobilization. Although N remobilization was not affected by IRMD in dryer year, it increased by IRMD (8.4%) in the relatively wet year. Totally, for a more sustainable farming system in arid Mediterranean conditions, integration of biofertilizer and chemical N fertilizer could be successfully used for increasing grain yield, WUE, and N remobilization of triticale, especially under deficit irrigation regimes.

Inappropriate use of chemical inputs damages soil beneficial microorganisms and consumer health. In order to reduce or eventually eliminate chemical inputs, bio-agroecosystems was founded. Azospirillum is one of the most studied genera as nitrogen fixing bacteria in agroecosystems. About 70 percent of the experiments have demonstrated the Azospirilum ability for increasing crop yield. Furthermore, some studies have shown that Azospirilum has a stress-reduction mechanism. Therefore, it seems that the Azospirilum is a suitable microorganism for low yielding conditions (water and N) of southern Iran. On the contrary, with respect to the importance of soil organic matter for microorganisms survival, its deficiency in soils of southern Iran is the biggest challenge for using the microorganisms as biofertilizers. Also, experiments on the interactive effects of crop residue, water deficiency and N sources (biological or chemical) on barley yield are quite scarce in southern Iran. Therefore, the aims of this study were to investigate the effects of crop residue management, different N sources (such as biological and chemical) and water stress conditions on barley yield in arid conditions of southern Iran (Fars province).

This research was conducted at the experimental farm of the Darab Agricultural College of Shiraz University during the 2017-2018 growing season. A split factorial layout based on a randomized complete block design with three replications was used. Treatments included: two irrigation levels as the main plots [1. Normal (IRN): irrigation based on the plant's water requirement up to the physiological maturity and 2. Deficit irrigation (IRDI): irrigation based on the plant's water requirement up to the anthesis stage (cutting of irrigation after anthesis)]. Also, subplots were two levels of plant residues [1. without residue, 2. returning 30% of wheat residues to soil] and four fertilizer sources [N0, no nitrogen fertilizer (control) ;N100, 100 kg N ha-1; Bio + N50, Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1 and Bio, Biofertilizer (Azospirillum brasilense)]. Biological yield and grain yield, yield components, plant height, spike length and chlorophyll content of flag leaf were measured. Then, the harvest index was calculated. Data were analyzed by using SAS 9.1 software and the means were separated using Duncan’s multiple range test at 5% probability level.

The results showed that the cutting of irrigation after anthesis could cause severe water stress in the grain-filling period of the barley life cycle and consequently reduction of 1000-seed weight, the number of seeds per spike and the number of fertile tillers per m2. The interaction effect of irrigation regime × N fertilizer source on grain yield was significant at 1% probability level. The highest grain yield was achieved in IRN and Bio + N50 (4049 kg ha-1). Water stress reduced grain yield at all N fertilizer sources as compared with IRN. However, this reduction was different in N fertilizer sources (24.1%, 46.8%, 44.3% and 22.1% in N0, N100, Bio + N50 and Bio, respectively). With respect to the lowest amount of grain yield reduction due to water stress in Bio and then in N0 treatments and economic considerations, N0 treatment can be recommended for use in the cutting of irrigation after anthesis (IRDI) strategy.

According to the results of this study, the highest barley grain yield achieved by the integrated N fertilizer [Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1] in normal irrigation. Deficit irrigation after anthesis significantly decreased barley grain yield at all N sources. Therefore, this irrigation regime was not recommended for barley farms of southern Iran. But if farmers intend to the cutting of irrigation after anthesis because of water resources deficiency, with respect to the lack of significant difference among N sources in this condition, it is recommended that no N fertilizer is applied.

In order to study the effect of different crop rotation systems on wheat grain yield and some soil properties, this experiment was conducted with seven rotation treatments in a randomized complete block design with four replications in Darab Agriculture Research Station. The experiment was repeated in two rotation frequencies: the first from 1999 to 2002 and the second one from 2002 to 2005 with the same crop treatments. Cropping systems were included 1. broad bean (Vicia sativa L.), corn (Zea mayse L.), chick ling vetch (Vicia villosa L.), and wheat (Triticum aestivum L.) (CS1) 2. clover (Trifolium sp. L.), cotton (Gossypium hirsutum L.), chick ling vetch, wheat (CS2) 3. broad bean, corn, sugar beet (Beta vulgaris saccharifera L.), wheat (CS3) 4. cotton, wheat, cotton, (CS4) 5. corn, wheat, corn, wheat (CS5) 6. wheat, canola (brasica compestris L.), wheat (CS6) 7. wheat, wheat, wheat (CS7). At the end of each rotation frequency, wheat grain yield and its components, soil organic carbon, phosphorous, potassium and bulk density was measured. At the end of second cropping cycle core index of soil different layers was also measured. Results of the experiment showed that CS2 had the highest amount of wheat grain yield in the first rotation frequency, without any significant difference with CS8, CS6 and CS4. The lowest wheat grain yield was for CS5 and CS3, respectively. In the second rotation frequency, wheat grain yield of CS6 was significantly higher than those of other crop systems, and the lowest was for CS5. The higher wheat grain yield of superior cropping systems such as CS2 and CS6 was due to higher kernel weight, more spike number per unit area and more kernel number per spike. The lower O.C. quality, lack of any follow and high nutritional requirements in CS5, resulted in lower wheat grain yield. Some soil chemical and physical properties, including O.C, P and K was also increased in high yielding cropping systems such as CS2 and CS7 in the first rotation frequency and CS6 in the second rotation frequency. Finally it could be concluded that presence of clover as a legume green manure in both short and long-term cropping cycle and canola with summer follow in rotation with wheat in long-term cropping cycle could result to increasing of wheat grain yield.