Cactus pear (Opuntia spp.) is an important resource in arid and semi-arid areas because of its ecological and socio-economic roles. The Moroccan newly implemented agriculture sector strategy Morocco Green Plan, Plan Maroc Vert included cactus as a major crop in many regions. In Morocco, because of a lack of research results, farming practices are very basic even if yields can significantly be improved. On the other hand research conducted in other countries (Italy, Mexico, etc.) showed that mineral nutrition is beneficial and largely soil type related. In order to improve agronomic practices INRA Agadir developed and implemented an agronomic research program on Cactus at Melk Zhar Experiment Station of INRA-Agadir. Mineral nutrition management is a key component of this project. The objective of the study was to determine the effect of nitrogen, potassium, phosphorus and magnesium amount on yield and quality of Opuntia ficus-indica. The treatments, applied on existing orchards and on newly planted ones, are: 0, 80 kg N/ha combined with 120 kg K/ha and 60 kg Mg/ha. The testing was conducted on 14 best ecotypes selected out of the national germplasm collection (with more than 200 ecotypes). The tests were conducted on a sandy soil with low organic matter content. The variables measured are: plant height, flowering, fruit yield component (weight, number/plant) and fruit sugar content. In general, the results indicate that measured variables showed differences among treatments. Nitrogen had significant impact on growth. Fertilization increased number of nopalitos three times, flowering started 5 to 15 days earlier compared to control. Regarding fruit quality, mineral nutrition improved Brix 1.5%. Finally, the different impacts induced by mineral nutrition improved general net return 15 to 25%.

The distribution and turnover of organic carbon (OC) and nitrogen (N) associated with aggregates in soils is critical for understanding the behaviour of C and N in soils. We collected soil samples from aspen (Populus simonii Carr.) woodland in the semi-arid Loess Plateau of China to investigate the distribution of aggregate-associated OC and N. The distribution of aggregates and aggregate-associated OC and N were measured, and OC and N stocks in each aggregate fraction were calculated. Across the sites and soil depths, microaggregates and the silt + clay fraction dominated the distribution of soil aggregates, which varied with site. Organic C and N accumulated mainly in the macro- and micro-aggregate fractions in loamy soils but in the silt + clay fractions in sandy soils. The OC and N stocks in the bulk soil of aspen woodland were determined by the OC and N stocks associated with silt + clay fraction. The results of this study indicate that soil texture may play an important role in assessing the distributions of soil OC and N in both bulk soils and aggregate size fractions in aspen woodland, especially in semi-arid regions. Furthermore, the establishment of aspen woodland would result in greater accumulation of OC and N in loam soils than in sandy soils.

Understanding soil evaporation in reforestation processes in an area of extreme drought is important. We examined the effects of drip-irrigated, high-salinity groundwater on the formation of soil salt crusts and subsequent soil evaporation in the Taklimakan Desert Highway Shelterbelt. Soil evaporation was measured using micro-lysimeters (MLS, 20 cm in length x 10 cm in diameter), and chemical characteristics, including SOM, total salts, ion composition and pH, were analyzed. The results showed that the inhibition efficiency of salt crusts on soil evaporation decreased from the surface to the lower soil layers. Following irrigation, the inhibition efficiency was 33.0% in the shelterbelt, which was much higher than the 13.8% observed for the bare soil. Total salt content and ion contents (Cl-, Na+, and SO42-) were much higher for the soil salt crusts than for shifting sandy soils, while the contents of other ions (Mg2+, K+, Ca2+, HCO3-, and CO32-) were very similar. The total salt content and ion composition of the salt crusts increased during the first 2 years of shelterbelt age, and decreased from 2 to 5 years. With the increasing age of the shelterbelts, the SOM of the salt crusts increased, whereas the total salts and pH decreased. We concluded that the formation of soil salt crusts results in reduced soil evaporation and the soil chemical condition functioned better for growth of the Taklimakan Desert Highway Shelterbelt.

Innovative strategies are needed to improve water and nutrient use efficiencies for sustainable production in sandy soils. Our objective was to determine the effects of applying cattle manure combined with zeolite and chemical fertilizer on (1) sunflower (Helianthus annuus L) yield and quality and (2) nutrient leaching under two irrigation regimes on a sandy soil in a semi-arid region of Iran. The experiment was carried out using a randomized complete-block design, with a split-plot arrangement of treatments and four replications. Irrigation regime (I-1: full irrigation and I-2: limited irrigation) provided the whole-plot treatments with five fertilization strategies (F1: urea, F2: urea + composted manure (CM) with 0% (w/w) zeolite, F3: urea + CM with 7% zeolite, F4: urea + CM with 14% zeolite and F5: urea + CM with 21% zeolite) providing the sub-plots. Our results showed that limited irrigation (I-2) significantly decreased dry matter yield by 10% in 2008 and 9% in 2009. Dry matter and seed yield were considerably improved by the application of manure + zeolite in both years, but the impact of their application was greater in the second year than in the first. In both years, the maximum seed protein content was achieved with the F-5 treatment, while minimum seed protein content was observed in the F-2 and F-1 treatments for 2008 and 2009, respectively. Maximum irrigation water productivity was found with the I2F5 treatment combination in 2009 (0.81 kg m(-3)), while the minimum value was found for the I1F1 combination in 2008 (0.48 kg m(-3)). The highest and lowest rates of nitrate leaching were obtained from the I1F1 (36 kg ha(-1)) and I2F5 (11 kg ha(-1)) treatment combinations, respectively. Fertilizing only with urea (F-1) resulted in the highest nitrate leaching across both irrigation regimes, while the integrated treatments (F-2, F-3, F-4 and F-5) significantly decreased nitrate leaching, compared to the F-1 treatment, particularly with full irrigation (I-1). Addition of zeolite to the CM also decreased P leaching but not as much as for nitrate leaching. We concluded that amending soil with manure and zeolite can be a beneficial approach for decreasing chemical fertilizer application rates and improving the sustainability of agricultural systems. (C) 2012 Elsevier B.V. All rights reserved.

Irrigation with treated wastewater (TWW) is commonly practiced in Israel to relieve freshwater (FW) shortages. We hypothesized that the organic matter (OM) originating from TWW irrigation alters the physico-chemical properties of the soil, induces water repellency in the soil's top layer, and consequently alters water distribution in the soil profile. In measurements taken in an avocado orchard on a clayey soil, water repellency was found in TWW-irrigated plots. In addition, smaller wetted surface areas were recorded around the drippers in comparison with FW drippers. Drier zone below soil surface was observed in TWW-emitting drippers. OM extraction from the different plots exhibited differences in quantity and quality of organic substances between TWW- and FW-irrigated soils, with a higher quantity of hydrophobic substances in the TWW-irrigated soil extract.

Considering extreme events of climate change and declining availability of appropriate quality water and/or highly productive soil resources for agriculture in dryland regions, the need to produce more food, forage and fibre will necessitate the effective utilization of marginal-quality water and soil resources. Recent research and practices have demonstrated that effective utilization of these natural resources in dry areas can improve agricultural productivity per unit area and per unit water applied. This paper focuses on the following three case studies as examples: (1) low productivity soils affected by high levels of magnesium in soil solution and on the cation exchange complex; (2) degraded sandy soils under rainfed conditions characterized by low water-holding capacity, organic matter and clay content and (3) abandoned irrigated soils with elevated levels of salts inhibiting growth of income generating crops. The results of these studies demonstrate that application of calcium-supplying phosphogypsum to high-magnesium soils, addition of clays to light textured degraded soils and phytoremediation of abandoned salt-affected soils significantly improved productivity of these soils. Furthermore, under most circumstances, these interventions were economically viable, revealing that the efficient use of marginal-quality water and soil resources has the potential to improve livelihoods amid growing populations in dry areas while reversing the natural resource degradation trend. However, considerably more investment and policy-level interventions are needed to tackle soil degradation/remediation issues across both irrigated and dryland agricultural environments if the major challenge of producing enough food, forage and fibre is to be met. Copyright (c) 2011 John Wiley & Sons, Ltd.

The aim of this work is to promote the use of local organic wastes (leaves, lifs, Kornav) of date palm, as organic fertilizer, to improve the microbiological activities of sandy soil, especially the process of carbon mineralization. To do this we adopted the method of incubation under controlled parameters on representative samples of sandy soils of arid regions. It is a sandy soil taken from the southern region of Algeria, Ouargla. The analysis of overall results demonstrated a positive and significant effect of date palm residues on soil microbial activity. Thus, after 42 days of incubation, the cumulative amounts of CO2 released are 14.37 and 40.02 mg/100 g dry soil, respectively in soil enriched and unenriched (control) by the residues of date palms. Regarding the influence of these residues on microbial density, we observed a stimulatory effect of functional groups studied (cellulolytic and amylolytic germs) as well as total and fungal microflora. The overall results show the advantage of using date palm residues for improving microbiological functioning and microbial density of the sandy soil of desert areas.

A survey of gasteroid fungi from arid regions in the La Rioja province (northwestern Argentina) resulted in 20 species of 13 genera. Each species is briefly commented on and descriptions are provided for taxa poorly known or with few records in the world. In addition, photographs of basidiomata and SEM micrographs illustrating basidiospores are provided for most of the taxa. The most noticeable records are Bovista grandipora, new for Argentina, Schizostoma argentinense with few records in the world, and Vascellum intermedium and Disciseda verrucosa, new for South America. In addition, the distribution of the species among the main types of habitat is discussed in relation to spore release and humidity.

This paper analyzes new fossil wood from El Palmar Formation (late Pleistocene) recovered from the El Palmar National Park, central-eastern Entre Rios province, Argentina. Two new morphospecies of Beilschmiedioxylon Duperon-Laudoueneix and Duperon 2005 (Lauraceae) and other of Terminalioxylon Schonfeld 1947 (Combretaceae) are described, as well as Piptadenioxylon chimeloi Suguio and Mussa 1978 (Fabaceae-Mimosoideae) is cited for the first time in Pleistocene deposits of Argentina. This species was described from the ancient alluvial Tiete River "Porto de areia of Itaquaquecetuba", Sao Paulo, Brazil. Wood anatomical characters suggest an affinity with the taxa Beilschmiedia taubertiana (Schw. and Mez) Kosterm., Terminalia australis Cambess, and Parapiptadenia Brenan respectively. The relationships and comparisons with the nearest living relatives were used to infer paleogeographic, paleoclimatic and pale-oecological requirements. This fossil record suggests warm and humid climatic conditions for central-eastern of Entre Rios, and during the period comprising the development of this geological formation. The fossil wood would correspond to components of riparian mixed forests (Lauraceae and Combretaceae) and semi-arid mixed forests (Fabaceae).

Background: The evolutionary history of the biota of North Africa and Arabia is inextricably tied to the complex geological and climatic evolution that gave rise to the prevalent deserts of these areas. Reptiles constitute an exemplary group in the study of the arid environments with numerous well-adapted members, while recent studies using reptiles as models have unveiled interesting biogeographical and diversification patterns. In this study, we include 207 specimens belonging to all 12 recognized species of the genus Stenodactylus. Molecular phylogenies inferred using two mitochondrial (12S rRNA and 16S rRNA) and two nuclear (c-mos and RAG-2) markers are employed to obtain a robust time-calibrated phylogeny, as the base to investigate the inter- and intraspecific relationships and to elucidate the biogeographical history of Stenodactylus, a genus with a large distribution range including the arid and hyper-arid areas of North Africa and Arabia. Results: The phylogenetic analyses of molecular data reveal the existence of three major clades within the genus Stenodactylus, which is supported by previous studies based on morphology. Estimated divergence times between clades and sub-clades are shown to correlate with major geological events of the region, the most important of which is the opening of the Red Sea, while climatic instability in the Miocene is hypothesized to have triggered diversification. High genetic variability is observed in some species, suggesting the existence of some undescribed species. The S. petrii - S. stenurus species complex is in need of a thorough taxonomic revision. New data is presented on the distribution of the sister species S. sthenodactylus and S. mauritanicus. Conclusions: The phylogenetic hypothesis for the genus Stenodactylus presented in this work permits the reconstruction of the biogeographical history of these common desert dwellers and confirms the importance of the opening of the Red Sea and the climatic oscillations of the Miocene as major factors in the diversification of the biota of North Africa and Arabia. Moreover, this study traces the evolution of this widely distributed and highly specialized group, investigates the patterns of its high intraspecific diversity and elucidates its systematics.