Plant Soil (2008) 302:45–52 DOI 10.1007/s11104-007-9453-8
REGULAR ARTICLE
Effects of alternate partial root-zone irrigation on soil microorganism and maize growth Jinfeng Wang & Shaozhong Kang & Fusheng Li & Fucang Zhang & Zhijun Li & Jianhua Zhang
Received: 22 May 2007 / Accepted: 17 October 2007 / Published online: 14 November 2007 # Springer Science + Business Media B.V. 2007
Abstract Partial root-zone irrigation creates a dynamic heterogeneous distribution of soil moisture that may affect the numbers and activities of soil microorganisms. In this study, three irrigation methods, i.e. conventional irrigation (CI), alternate partial rootzone irrigation (APRI, alternate watering on both sides of the pot) and fixed partial root-zone irrigation (FPRI, fixed watering on one side of the pot), and three watering levels, i.e. well-watered, mild and severe water deficit, were applied on pot-grown
Responsible Editor: Rana E. Munns J. Wang : S. Kang : F. Zhang : Z. Li Key Lab of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest Agriculture and Forestry University, Yangling, Shaanxi, China, 712100 S. Kang (*) Center for Agricultural Water Research in China, China Agricultural University, Beijing, China, 100083 e-mail:
[email protected] F. Li Agricultural College, Guangxi University, Nanning, Guangxi, China, 530005 J. Zhang (*) Department of Biology, Hong Kong Baptist University, Hong Kong, China e-mail:
[email protected]
maize. Numbers of soil microorganisms, plant height, stalk diameter, leaf area and biomass accumulation were monitored over the treatment period. A quadratic parabola relationship between the number of soil microorganisms and soil water content was found, indicating the number of soil microorganisms reached a peak at the mild soil water deficit condition, possibly due to better soil aeration. The peak number of soil microorganism was obtained when soil water content was 66, 79 and 75% of field capacity for CI, FPRI and APRI, respectively. Soil microorganisms were evenly distributed in both sides of APRI and their total numbers were always higher than those under other two irrigation methods for the same soil water content. The count of soil microorganisms in the dry root zone of FPRI was reduced by a lack of water. Maximum biomass accumulation was obtained under well watered condition but severe water deficit led to a 50% reduction in the CI treatment. Such reduction was much smaller under APRI and therefore the highest water use efficiency was obtained. Our results suggest that APRI maintained the best aeration and moisture condition in the soil and enhanced the activities of soil microorganisms, which might also have benefited the plant growth.
Keywords Irrigation method . Partial root-zone drying/irrigation . Soil microorganism . Soil water deficit . Plant growth . Maize (Zea mays)
DO09453; No of Pages
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Plant Soil (2008) 302:45–52
Introduction
Materials and methods
Alternate partial root-zone irrigation (APRI) is a way of reducing irrigation water (Davies et al. 2000; Dry and Loveys 1998; Kang et al. 1997; Kang et al. 1998). APRI can improve plant water use efficiency without much yield reduction (Kang and Zhang 2004; Du et al. 2005), and is relatively easy to apply. An earlier study found that root development in maize was significantly enhanced by alternate furrow irrigation that maintained high grain yield with up to 50% reduction in irrigation amount, while fixed furrow irrigation and conventional furrow irrigation all showed a substantial decrease in yield with reduced irrigation (Kang et al. 2000). Many physiological and morphological changes of different crops under APRI have also been reported (Kang et al. 2001, 2002, 2003; Kang and Zhang 2004; Skinner et al. 1999; Zegbe-Domínguez et al. 2003). APRI can lead to heterogeneous distribution of soil moisture and may affect rhizosphere soil biological environment. Soil microorganisms play important roles in soil quality and plant productivity (Hill et al. 2000). The microbial biomass in soil constitutes a pool of nutrients that has a rapid turnover when compared with soil organic matter (Bååth and Anderson 2003). Therefore, quantitative and qualitative changes in the composition of soil microbial communities may serve as an important and sensitive indicator of both short and long-term changes in soil health (Hill et al. 2000). Soil microbial communities may be strongly influenced by agricultural practices that change the soil environment (Lundquist et al. 1999). Many studies have been conducted to assess the influence of different field practices and irrigation methods on the composition and physiology of the soil microbial community (Drenovsky et al. 2004; Rietz and Haynes 2003; Stromberger et al. 2007), but there are few reports on soil microbial population and distribution responses to APRI. The soil water status could have large effects on the physiology and structure of the soil microbial community (Williams and Rice 2006). The objective of the present experiment was to assess soil microbial population and distribution in response to different irrigation methods and irrigation levels during the growing season. This study investigates the relation between soil water content and the number of soil microorganisms, as well as the effects of APRI on crop growth and water use efficiency.
The experiment was carried out in a greenhouse in Key Lab of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest Agriculture and Forestry University from March to July 2005. Maize plants (Zea mays L. cv. Hudan No. 4, a local variety) were grown in pots (26 cm in diameter, 27 cm in depth) filled with 14 kg air-dry soil per pot. Soil was sieved by 2 mm mesh and mixed with fertilizer to keep soil structure, nutrition and soil microorganism homogeneous at the beginning. The soil bulk density was 1.3 g/cm3, soil pH was 7.87 and organic matter content was 6.08 g/kg. The soil had a total N content at 0.89 g/kg, total P content at 0.72 g/kg, total K content at 13.80 g/kg, available N (i.e. hydrolytic N, 1 mol/L NaOH hydrolysis) at 55.93 μg/g, available P (0.5 mol/L NaHCO3) at 8.18 μg/g and available K (1 mol/L neutral NH4OAc) at 102.30 μg/g. Soil texture was heavy loam soil and field water capacity was 26% (mass basis). The inside of all pots was evenly separated into two containers with plastic sheets sealed in the middle such that water exchange among the containers was prevented. Each container was filled with 7 kg air-dry soil. Seeds were placed at the middle of the pots so that their primary roots were fairly evenly distributed into the two separated containers. In addition, a PVC tube (2 cm in diameter) with holes was installed in each container to supply irrigation water to prevent surface soil hardening from the irrigation and reduce evaporation. Treatments included three irrigation methods and three watering levels. Their combination yielded nine treatments (i.e. 3×3) and each treatment was replicated five times. Irrigation methods included conventional irrigation (CI, soil was evenly irrigated with tap water in each watering), alternate partial root-zone irrigation (APRI, watering was alternately applied to the two parts in the pot in consecutive watering) and fixed partial root-zone irrigation (FPRI, watering was fixed to half of the soil in the pot). Three watering levels included severe water deficit (40–50% of field capacity), mild water deficit (50–65% of field capacity) and wellwatered (65–80% of field capacity) during the seedling stage and severe water deficit (50–60% of field capacity), mild water deficit (60–75% of field capacity) and well-watered (75–90% of field capacity) after the seedling stage. Fertilizers were applied with 0.20 g N/kg dry soil, 0.1 g P2O5/kg dry soil and 0.07 g K2O/kg dry
Plant Soil (2008) 302:45–52 25
20
Soil water content (%)
Fig. 1 Variation in soil water content (mass basis) for CI, FPRI and APRI treatments in the maize growing season. Bars denote standard errors of the mean. Bars and lines joining points in APRI are omitted for clarity. Treatment codes are the same as in Table 1
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soil for all treatments. N was supplied as urea. P and K were applied in KH2PO4 form. All fertilizers were applied with analytical reagents and mixed into the soil in powdered form at the commencement of the experiment. And soil water regime in all pots was kept 100% of field capacity before seeding. Seeds were sown on 20 March 2005, with one sprouting seed per pot. When the seedlings had between three and four leaves, all pots began to control soil water content. Before the soil water was controlled, soil water regimes in all pots were kept the well-watered (65–80% of field capacity). After soil water was controlled, soil water contents in each
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treatment were measured with Type HH2 soil moisture device (Delta-device Ltd. Cambridge, UK). Irrigation was strictly controlled when soil water content reduced to or near to the lower limit of soil water content. Crop water consumption (evapotranspiration) and the amount of irrigation were calculated from the pot water balance. In FPRI treatment, fixed watering root-zone was called irrigated (wet) rootzone and no watering root-zone was called nonirrigated (dry) root-zone. In APRI treatment, alternate watering root-zone before collecting soil sampling was called wet root-zone, no watering root-zone was called dry root-zone.
W well-watered, M mild water deficit, Se severe water deficit, Wet irrigation root zone under fixed partial root-zone irrigation (FPRI) or irrigation root-zone before taking soil sample under alternate partial root-zone irrigation (APRI), Dry no irrigation root zone under FPRI or no-irrigation root-zone before taking soil sample under APRI, CI conventional irrigation. Means with different letters in the same row indicate significantly different at P