Análisis del diario de observación

Irrigation water quality significantly influenced the chemical properties of both the sandy loam topsoil and medium clay subsoil horizons of a texture-contrast soil (Brown Sodosol) in a dry subhumid warm climate. Irrigation with 16 dS/m water resulted in significantly higher ECse, Cl‾, and ESP in the upper soil profile. These changes are expected to dramatically impact the growth and yield of almost all crops. Saline irrigation resulted in the variable depth displacement of the base nutrient cations based on their physio-chemical properties (>K+ >Mg2+ >Ca2+). The leaching of these ions from the upper profile has induced a nutritional imbalance in the main root zone area, and caused

130 accumulation of Na+ and Cl‾ to levels potentially toxic to traditional crops. At a soil depth of 10 – 30 cm irrigation with 16 dS/m water reduced Mg 2+ 13-fold, Ca2+ four-fold and K+ five-fold compared to the control plot. Irrigation with 16 dS/m water increased exchangeable Na+ approximately five-fold to that of the control. We interpret this as Na+ displacing of Ca2+, Mg2+ and K+ to greater depths in the soil. This cation displacement reduced the subsoil ESP leading to a beneficial reduction in the subsoil pH.

Irrigation with 16 dS/m water significantly increased both sodicity (ESP) and salinity (EC) in the topsoils (<50 cm). High ESP (>15) in non-saline soils has been linked to declines in soil porosity, permeability and water holding capacity elsewhere. The significant negative correlation between TOC and ECse indicates that high saline irrigation can decrease a key measure of soil health. However irrigation with 0.8 dS/m water which is equivalent to the salt concentration of domestic recycled water used for irrigation in the region, had no significant effect on soil ECse, ESP, TEB and Cl‾ at most depths after 2.5 years. Consequently use of 0.8 dS/m water for irrigation appears sustainable at least over the short term, whilst irrigation of 16 dS/m water (the salinity in waste water produced from CSG extraction) at 800 mm/yr, and to a lesser extent 200 mm/yr, resulted in detrimental changes in soil chemical properties that are expected to severely impact the growth and yield of most crops and pastures.

*To be submitted toSmall Ruminant Research 131

Chapter 7

Productivity and forage quality of

Atriplex

lentiformis, Atriplex halimus and Medicago arborea

grown in response to irrigation with saline water*

Suresh Panta1, David Parsons1, Peter Lane1, Richard Doyle1, Tim Flowers3, Gabriel Haros2 and Sergey Shabala1

1

School of Land and Food, University of Tasmania, Hobart, Australia; 2The Punda Zoie Company Pty Ltd, Melbourne, Australia; 3School of Plant Biology, Faculty of Natural & Agricultural Sciences, The University of Western Australia, Crawley, Australia

Abstract

The aim of this study was to quantify differences in the yield and the nutritive value of

Atriplex lentiformis, Atriplex halimus and Medicago arborea as irrigated forage crops in Brown Sodosol. Plants were irrigated with sodium chloride dominated saline water with an electrical conductivity of 0.8, 8 and 16 dS/m at the rate of 200, 500 and 800 mm/year rate. The nutritive value of the three plants was assessed on the basis of acid detergent fibre (ADF), neutral detergent fibre (NDF), dry matter digestibility (DMD), dry organic matter digestibility (DOMD), crude protein (CP), ash content and metabolisable energy (ME), as well as the concentration of selected minerals nutrient such as calcium (Ca), potassium (K), sodium (Na) and phosphorus (P). The dry matter (DM) yield of Atriplex

species was increased with increasing salinity level but DM yield of M. arborea was significantly reduced, 2.7 t/ha/year at 16 dS/m water salinity compared to 8.3 t/ha/year at 0.8 dS/m salinity level. The tissue Ca, K, P and Na content varied between species where

M. arborea had high Ca (1.6%) but others minerals were higher in Atriplex species. In

Atriplex species Ca content was increased with increasing water salinity but it was reduced in M. arborea. Overall, the ash percentage and Na content in plant tissue increased with salinity treatment while this trend was opposite for NDF and K content. The CP of all species ranged from 15.5 to 16.5 % of DM which is comparable to

132 conventional forage species such as alfalfa. The ME of Atriplex species was 8 MJ/kg DM but lower than M. arborea (10 MJ/kg DM). M. arborea had higher DMD (67 % of DM), DOMD (64 % of DM) and NDF (23 % of DM) content than Atriplex species. Overall, the CP, DMD, DOMD and ME values were low at 16 dS/m salinity irrigated at 800 mm/year rate. Based on the observation of selected nutritional parameters, these plants can be used as alternative sources of forage for ruminants during periods of feed shortage. Although they possess all the nutrients that are required for ruminants it may not be suitable to feed as sole source of diet as it has high Na content and may have some non nutritional factors which we have not investigated in this experiment .

Keywords: Soil salinity; Soils sodicity; Soil chemical properties; Exchangeable cations.

7.1. Introduction

Globally, halophytic plants are widely distributed in many arid and saline areas and provide an alternative food source for grazing animals (Swingle et al., 1996, Masters et al., 2007; Panta et al., 2014). Palatable halophytic species are often grazed by sheep, goats, camels and wild animals (Gihad and El Shaer, 1994). Animals such as sheep and goats (Swingle et al., 1996, Ben Salem et al., 2010), camels, and cattle (Khan and Ansari, 2008) perform well on certain halophyte-based feeds. However, the successful use of halophytes as forage for livestock production also depends on their biomass production, nutritive value and voluntary feed intake (Norman et al., 2013).

A number of researchers have explored the possibility of halophytes as livestock feed (Glenn et al., 1992; Riley et al., 1994) and more specifically when grown as irrigated crops (Glenn et al., 1991; Miyamoto et al., 1994; Riley and Abdal, 1993). The yield, nutritional qualities and feeding value of some halophytic plants are comparable to conventional forages (Glenn et al 1999, Masters et al., 2007; Khan et al., 2009) but in some species high content of some minerals e.g NaCl, anti-nutritional compounds and non-protein nitrogen affect their use in animal diets (Benjamin et al., 1992, Glenn et al., 1999; Rogers et al. 2005, El Share, 2010). In addition, many researchers reported that halophytic forage fed animals had lower appetite, growth rate and meat quality compared

133 to those fed on conventional forages (Gihad and El Shaer, 1994; Glenn et al., 1994; Miyatmoto et al., 1994). In contrast, some researchers described a positive effect of halophytic forage on meat quality (Khan and Ansari, 2008) and no negative effect on animal performance (Al- Shorepy et al., 2010; Khan et al., 2009). However, the general nutritional value varies by species, plant age and growing environment, for instance, irrigation water quality (Swingle et al 1996; Robinson et al., 2004). It may also depend on the combination of both salinity and irrigation regime. If plants are stressed they have a tendency to accumulate various secondary metabolites which may have an important protective (antioxidant) role but detrimental to animal health. So, a balance between commercially-acceptable levels of production and nutritional quality is important for the sustainability of these crops as alternative forages.

Halophytic shrubs, especially from the Chenopodiaceae family, are planted in agricultural areas to provide feed for livestock and rehabilitation of salt affected land (Masters et al., 2010). In addition, the International Center for Biosaline Agriculture (ICBA) has also been conducting several collaborative projects with research organizations in Saudi Arabia, Pakistan and Bangladesh for the development of bio-saline fodder and forage production using Atriplex species (A. halimus, A. nummularia and A. lentiformis (ICBA, 2007). These plants are often grown on abandoned land where nothing else grows, and there has been little attempt to identify the effect of growing conditions on the nutritional value of these plants.

Previous studies on Atriplex species have provided some information on plant biomass yield (Watson, 1990; Watson and O‘Leary, 1993) and the effect of an Atriplex

base forage diet on milk yield and growth rate in animals (Abu-Zanat and Tabbaa, 2006), feeding quality (Alicata et al., 2002), grazing preference (Norman et al., 2004), mineral content (Watson et al., 1994) and to a lesser extent on the effect of growing conditions on the nutritional quality of the plants (Masters et al., 2010). The aim of this study was to determine the effect of different concentrations of saline water (dominated by NaCl salt), applied under different irrigation regimes on the nutritive value of Atriplex lentiformis, Atriplex halimus and Medicago arborea.

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