Saffron response to irrigation water salinity, cow manure and planting method
Introduction
Increasing demand for water in the world, especially in the arid and semiarid regions, has forced farmers to use poor-quality water such as saline water for irrigation. Salinity is one of the serious environmental problems that causes osmotic stress and reduction in plant growth and crop productivity in irrigated areas (Katerji et al., 2003, Asgari et al., 2012). In the arid and semi-arid regions, the main water resource for irrigation is well water, which suffers increasing salinity and, because of limited water resources, more effective use of this resource is emphasized.
When saline water is used for irrigation, new approaches are needed that address the production sustainability. Greater attention should be given to minimize salinity in the root zone (Oster, 1994, Shalhevet, 1994, Gideon et al., 2002, Katerji et al., 2003, Katerji et al., 2004). Several authors have indicated the need to select appropriate irrigation systems and practices that will provide sufficient water to meet the evaporative demand and minimize salt accumulation in the soil (Bresler et al., 1982, Munns, 2002). Several strategies can be used for reducing the effects of irrigation water salinity on crop yield, such as: cultivation of salinity resistant cultivars (Ahmadi and Niazi-Ardakani, 2006, Zamani et al., 2010), leaching the soil to prevent salt accumulation and changing the planting method such as cultivating plants in furrows (Dong et al., 2010, Zhang et al., 2007, Shabani et al., 2013). Furrow irrigation with saline water causes salt accumulation on ridges and decreased soil salinity in the furrows (Wadleigh and Fireman, 1949). Proper conditions for plant growth are provided with in-furrow planting method, due to higher soil moisture, reduction in evaporation from the soil surface, and higher salt leaching (Zhang et al., 2007, Li et al., 2008, Li et al., 2010, Quanqi et al., 2012). Shabani et al. (2013) examined the effects of deficit irrigation with different salinity levels and planting methods (in-furrow and on-ridge), as strategies for coping with water and salinity stresses on yield and yield quality of rapeseed. They indicated that planting in-furrow increased yield by 5.3% and 13.7% in the first and second years, respectively, relative to on-ridge planting.
Soil amendments such as manure also can mitigate the impacts of water salinity stress on crop production. Manure improves soil conditions, such as increasing the pH in acid soils, increasing soil water-holding capacity, hydraulic conductivity and infiltration rate, and reducing soil bulk density. Manure also is a good source of plant nutrients and improves soil structure (Barbarick, 1996, Mkhabela, 2006, Mahmoodabadi et al., 2010). Ould-Ahmed et al. (2010) suggest that farmyard manure is an efficient amendment for sandy soil with saline water irrigation. However; poultry manure is not appropriate for use in conjunction with saline water irrigation, as it accentuates salinity stress.
Saffron (Crocus sativus L.) is a strategic export crop and the most expensive spice in the Islamic Republic of Iran. It is produced largely in the Khorasan and Fars Provinces that have arid and semi-arid climates, respectively (Abrishami, 1987). Although saffron does not contribute directly to food security, its low water requirement and high income generate interest when considering sustainable agriculture. Effects of planting methods and corm density (Behnia, 2009, Naderi-Darbaghshahi et al., 2009), chemical and organic fertilizers (Arslan et al., 2009, Omidi et al., 2009), corms weight and size (Nassiri Mahallati et al., 2007) on saffron have been investigated. Saffron is traditionally planted and irrigated by basin irrigation method in Iran. Azizi-Zohan et al. (2006) indicated that, in a semi-arid region of Fars Province of Iran, basin irrigation at intervals of 24 days was superior to furrow irrigation (planting on ridge) with more frequent irrigation intervals. Sepaskhah and Yarami (2009) examined the interaction effects of salinity and irrigation regime in a pot experiment, finding that saffron yield and corm production are most sensitive to soil water salinity and least sensitive to soil moisture depletion. At present, no research has been conducted to investigate the effect of irrigation water salinity, manure application, and planting methods on saffron under field conditions. Thus, in our study, we endeavor to examine the effects of irrigation water salinity, cow manure levels and planting methods on yield and growth of saffron (C. sativus L.) plant in a silty clay loam soil.
Section snippets
Site description
This research was conducted during two production seasons from 2011 to 2013 at the Experimental Station of Agricultural College, Shiraz University, in Badjgah region at 29°56′N, 52°02′E and 1810 m above the mean sea level, in southwest of Iran. The climate is semi-arid, with long-term average air temperature, relative humidity, and precipitation values of 13.4 °C, 52.2% and 387 mm, respectively. The soil at the experimental site is silty clay loam up to 0.9 m depth (Table 1). Chemical analysis of
Results
Fig. 1 illustrates cumulative ETo, irrigation events and rainfall for two growing seasons. The total amount of irrigation water applied was 207 mm and 263 mm for the first and second growing seasons, respectively. Total rainfall was 363 mm and 445 mm during the growing periods in 2011–2012 and 2012–2013, respectively. The saffron corms were planted during their dormant period in summer, and saffron growth started as a result of the first irrigation in each growing season. Thus, the figures depict
Treatment effects on saffron yield
Saffron yield was significantly influenced by irrigation water salinity, cow manure, and planting method. Saffron yield declined by about 38% when increasing water salinity to its highest level.
Saffron yield for the in-furrow planting method was more than 3.5 times higher than the basin planting, indicating that the in-furrow planting method is an efficient method for saffron production. The reason for higher saffron yield with the in-furrow planting method is probably due to favorable soil
Conclusions
Our results showed that saffron yield was more affected by planting method compared with the salinity and fertilizer levels. Results indicated that higher application rate of cow manure (60 Mg ha−1) resulted a higher harvest index in both growing seasons. Also, harvest index of the in-furrow planting method were 144% and 73% higher than those in the basin planting method in the first and second seasons, respectively. Salinity-yield production functions indicated that the sensitivity of different
Acknowledgements
This research was supported partly by the Research Project funded by grant no. 93-GR-AGR 42 of Shiraz University Research Council, Drought National Research Institute, and Center of Excellence for On-Farm Water Management. We appreciate also the helpful comments of two anonymous reviewers.
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