Growth and nitrogen fixation of legumes at increased salinity under field conditions

Research Article SPECIAL ISSUE: Physiology and Ecology of Halophytes—Plants Living in Salt-Rich Environments Growth and nitrogen fixation of legumes at increased salinity under field conditions: implications for the use of green manures in saline environments

Bas Bruning1*, Richard van Logtestijn1, Rob Broekman1, Arjen de Vos2,3, Andre´s Parra Gonza´lez2 and Jelte Rozema1

1 Systems Ecology, Department of Ecological Science, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam, The Netherlands

2 Salt Farm Texel, Den Burg, The Netherlands

3 Department of Biological Oceanography, Royal Netherlands Institute for Sea Research (NIOZ), Den Burg, The Netherlands

Abstract

The use of legumes as green manure can potentially increase crop productivity in saline environments and thus contribute to the sustainability of agricultural systems. Here, we present results from a field experiment conducted in the Netherlands that addressed the efficiency of nitrogen (N) fixation by a legume at varying salinities. We grew Melilotus officinalis in an agricultural field using drip irrigation with water salinity varying in electrical conductivity between 1.7 and 20 dS m21 . In the experiment, nearly 100 % of total plant N in M. officinalis was derived from symbiotic fixation at all but the highest salinity level (20 dS m21 ). Our results indicated that this species derived substantial amounts of N via symbiotic fixation, the N becoming available in the soil (and thus available to crops) when cultivated legumes senesce and decompose. Based on the growth performance of M. officinalis and its ability to fix N at moderate soil salinity in our field experiments, we identified this species as a promising source for green manure in saline agriculture in temperate regions.

 

Table 2. Data on symbiotic nitrogen fixation from the scientific literature. Nitrogen fixation performance at different salinities is calculated on
the basis of the Acetylene Reduction Assay (ARA at 0 mM NaCl taken as 100 %) for all species except for Sesbania sesban, in which case relative
nodule dry weight is taken as a proxy for N fixation. *For Sesbania sesban: reduction in nodule dry weight as compared to nodule dry weight at
0 mM; for all other species reduction in ARA as compared to ARA at 0 mM NaCl. **Fresh weight for S. rostra, the other species total dry weight. For
all species, weight is expressed relative to the weight at 0 mM of NaCl. ***Actinorrhizal species (not a legume). 1Mahmood et al. (2008),
2Hopmans et al. (1983), 3Jungklang (2003), 4Ng (1987).
Species NaCl(mM) Nitrogencontent (%) Relative N-fixation performance* Relative weight** Duration of treatment (days) Method
Sesbania sesban1 0 0.48 100 100 80 3 L soil in pots
  34 0.38 79 91.2 80 3 L soil in pots
  69 0.35 73 82.1 80 3 L soil in pots
  103   71 76.9 80 3 L soil in pots
  131 0.33 64 72.8 80 3 L soil in pots
  172 0.04 31 69.9 80 3 L soil in pots
Acacia dealbata2 0 1.79 100 100 25 200 g sandy loam in pots
  25 1.89 99 93.3 25 201 g sandy loam in pots
  75 1.62 71 88.4 25 202 g sandy loam in pots
  150 1.55 46 86.3 25 203 g sandy loam in pots
  250 1.67 17 58.9 25 204 g sandy loam in pots
Sesbania rostrata3 0 3.92 100 100 50 Hydroponics
  25 3.9 86 90 50 Hydroponics
  50 3.73 113 83.3 50 Hydroponics
  100 3.6 84 71.1 50 Hydroponics
  150 3.32 5 41.1 50 Hydroponics
  200 3.62 0 27.8 50 Hydroponics
Casuarina 0 1.9 100 100 168 Sand in pots
equisetifolia4,*** 20 1.9 108 81.9 168 Sand in pots
  50 1.5 83 136.6 168 Sand in pots
  100 1.6 85 132.1 168 Sand in pots
  200 1.8 98 104.2 168 Sand in pots
  500 1.7 42.5 41.9 168 Sand in pots

Keywords: Halophytes, Melilotus officinalis, salinity, Sesbania, symbiotic nitrogen fixation

Source: AOB PLANTS open access journal as pdf file (downloadable)

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