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The phenotypic diversity and productivity of a diverse alfalfa (M. sativa subspp.) panel of cultivars, landraces and wild relatives with putative drought tolerance were evaluated in two Mediterranean environments (central Chile and Southern Australia). In Chile, 70 accessions were evaluated in rainfed conditions and in Australia 30 accessions under rainfed and irrigated conditions, during three growing seasons. Large phenotypic variation was observed among and within subspecies for NDVI, stem length, intercepted PAR and forage yield. Principal component analysis indicated that the first two principal components (PC) accounted for 84.2% of total variance, fall dormancy, taxa, and breeding status were closely related to the agronomical performance of alfalfa accessions. Forage yield varied largely among accessions across years and locations. A linear relationship was found between annual forage yield and annual water added to the experiments (R2 = 0.60, p &lt, 0.001). The GxE analysis for forage yield allowed the detection of the highest yielding accessions for each of the two mega-environments identified. The accessions CTA002 and CTA003 showed greater forage yield in both Chile and Australia environments. It is concluded that new breeding lines derived from crosses between cultivated alfalfa (M. sativa subsp. sativa) and wild relatives belonging to the primary (M. sativa subsp. falcata) and tertiary (M. arborea) gene pool, achieve outstanding agronomical performance in drought-prone environments.

The potential for alfalfa to be a valuable rainfed pasture option that can be used to increase livestock and crop production in central-south Chile is demonstrated for the first time. The persistence, productivity and water use efficiency of alfalfa (Medicago sativa) cultivars was evaluated at four sites in dryland Mediterranean environments of Chile between 2012 and 2015. Nine alfalfa cultivars were evaluated for plant persistence, winter growth, forage yield, shoot water potential (Ψ), stomatal conductance (gs), and carbon (δ13C) and oxygen (δ18O) compositions. The percentage of plant survival after four years varied between 69 and 97% of the established plants. Alfalfa forage yield was >9 t ha−1yr−1 at Yungay (Andes foothills) in year two, and at Cauquenes (interior dryland site) in years three and four. The highest forage yield was obtained in cultivars SARDI Ten and Aquarius and the lowest in WL326HQ. In 2015, the forage yield during late spring and early summer (November 2015–January 2016) ranged from 3170 to 3570 kg ha−1 (average of the nine cultivars), which represented between 29% and 38% of the total production. The response of gs to Ψ was different among cultivars but all cultivars exhibited a strong decline when Ψ was 16 kg mm−1). It is concluded that alfalfa is a high yielding forage that can extend the growing season into early summer and autumn in dryland Mediterranean environments.

Annual legume pastures exhibit high resilience and productivity in Mediterranean climate regions and can be an important source of nitrogen (N) for temperate cereals in integrated livestock production systems. This work seeks to evaluate the inputs of N fixed by annual legume mixtures (composed of 3–4 species and cultivars) grown for one, two or three years in a cropping sequence, and their contribution to soil N availability, N uptake and the grain yield of wheat, and compares this with the cereal rotation of oats and wheat with and without N fertilizer. Two field experiments comprising annual legume-wheat rotations were carried out in two contrasting Mediterranean environments in central Chile, the interior dryland in the eastern part of the coastal mountain rage, and the Andean foothills, over four growing seasons (2008–2011). At both experimental sites two mixtures of annual legumes were used in rotation with wheat. The duration of the pasture phase was between one and three years. In the interior dryland, the shoot DM of mixture M1 (T. subterraneum + M. polymorpha + T. michelianum) was higher than M2 (T. subterraneum + B. penicilius + O. compressus), and in the Andean foothills M4 (T. subterraneum + T. vesiculosum + O. compressus) was more productive than M3 (two cv. of T. subterraneum + T. incarnatum). The amount of N2 fixed by the legume mixtures, estimated by the 15N natural abundance technique, ranged between 28 and 87 kg N ha−1 in the interior dryland, and between 176 and 385 kg N ha−1 in the Andean foothills, representing respectively around 25 and 23 kg N ha−1 fixed for every Mg of shoot DM accumulated by the annual legumes. Wheat grain yields following legume mixtures represented 53–104 % of the 3.39 Mg ha−1 produced after oats with N fertilizer in the interior dryland, and between 68 and 101 % of 6 Mg ha−1 attained after oats in the Andean foothills, in 2011. N use efficiency (NUE) of wheat was significantly (P ≤ 0.05) higher in legume-based crop rotation than after oats with or without N fertilizer, at both sites. Legume mixtures also improved the N uptake (NUPE) and N utilization (NUtE) efficiencies of wheat compared to those observed after oats with N fertilizer, at both sites. Important differences among legume mixtures and the duration of the pasture phase were observed at both sites.

The absorption and partitioning of N is determined by its availability and demand during the various phenological stages of the crop. In two experiments conducted in rainfed areas of the Mediterranean climate region of central Chile, legume-wheat (Triticum aestivum L.) rotations were compared to oat (Avena sativa L.)-wheat systems (with and without applications of N fertilizer). The objective was to assess the contribution of legumes to the availability of soil N and N uptake by the wheat crop following grain legumes. N mineralization and uptake, N use efficiency (NUE), and N uptake efficiency (NUpE) by wheat were evaluated at different phenological stages in 2010. Synchronization existed between accumulated soil N mineralization and N uptake by the wheat. N uptake by wheat was higher in Experiment II (Andean foothill) than in Experiment I (interior dryland). Grain yields after legumes ranged 60-110% and 72-103% of yields in the fertilized cereal rotation (oat-wheat) in Experiments I and II, respectively. There was high correlation between soil N availability vs. grain yield (R² = 0.84 and 0.64) and N uptake vs. grain yield (R² = 0.55 and 0.64) for Experiments I and II, respectively. Rotations with lupine (Lupinus spp.) and field peas (Pisum sativum L.) showed high NUE and NUpE in Experiment I, and Experiment II in pea. The lowest NUE was after oats with N fertilizers. It is concluded that wheat cultivated in both agro-ecological areas after grain legumes or green manure was more efficient in N uptake and use than cereal, especially when the latter was fertilized.

Lucerne (alfalfa, Medicago sativa L.) is grown extensively worldwide owing to its high forage biomass production and nutritional value. Although this crop is characterised as being tolerant to drought, its production and persistence are affected by water stress. Selection of genotypes of high yield potential and persistence after a long period of drought is a major objective for lucerne-breeding programmes in Mediterranean environments. This selection could be enhanced and accelerated by the use of physiological and productivity traits and their estimation through remote-sensing methods. A set of nine cultivars of lucerne from Australia and the USA were assessed in four locations in Mediterranean central-south Chile. Several physiological and productivity traits were evaluated: forage yield (FY), stomatal conductance (gs), water potential (WP), leaf area index (LAI), nitrogen (N) content, and isotope composition (δ13C and δ18O) of the dry matter. Spectral-reflectance data were used to estimate the traits through spectral-reflectance indices (SRIs) and multivariate regression methods. For the SRI-based estimations, the R2 values for each assessment were

The potential benefits of using a legumes have not been evaluated in the rainfed, cropping systems of central Chile where wheat (Triticum aestivum) is typically grown in rotation with oats (Avena sativa) using high rates of nitrogen (N) fertilizer. Two experiments were initiated to compare unfertilized legume-wheat cropping sequences to the current oat–wheat system without and with applications of N fertilizer (160 or 207 kg N ha−1). One experiment was located in the interior dryland of central Chile (average annual rainfall 650 mm), and the other in the Andean foothills (average annual rainfall 1200 mm). Treatments were established in different areas of the same two experimental sites in consecutive years (2008 and 2009) resulting in four separate trials evaluating legume effects on wheat yield (2009 or 2010). Estimates of N2 fixation determined using the 15N natural abundance technique indicated that around 21 kg shoot N was fixed for every tonne (t) of shoot dry matter accumulated by either narrow-leaf lupin (Lupinus angustifolius), field peas (Pisum sativum), yellow lupin (Lupinus luteus), or white lupin (Lupinus albus) grown for grain, and by vetch (Vicia atroporpurea) grown in association with oats for green manure. When the amounts of N2 fixed were adjusted to account for N in the nodulated roots, narrow-leaf lupin was calculated to have returned the lowest average net inputs of fixed N to the system following grain harvest (26 kg N ha−1) and field pea the highest (192 kg N ha−1). By comparison vetch in the green manure treatments where all above-ground biomass were incorporated into the soil returned 67 kg fixed N ha−1. Depending upon location and year, growing grain legumes increased the subsequent N uptake by wheat by up to 60 kg N ha−1 (average 35 kg N ha−1) and vetch + oats green manure up to 103 kg N ha−1 (average 50 kg N ha−1). Wheat yields after grain legumes ranged from 2.4 to 3.0 t ha−1 in the interior dryland and 5.4–6.4 t ha−1 in the Andean foothills which were respectively 72–110% (90% average) and 69–83% (75% average) of the yields achieved by N fertilized wheat. Wheat yields after the vetch + oats green manure were 1.8 and 7.9 t ha−1 representing 60% and 102% of the yield of N fertilized wheat. In the absence of N fertilizer or legumes wheat yields after oats were around half that of the N fertilized wheat. It was concluded that grain legumes or legume-based green manures provide opportunities to greatly reduce the reliance of wheat production upon N fertilizer.

Soil organic carbon (SOC) plays a key role in crop productivity and soil quality. Conservation agriculture has a positive effect on SOC accumulation in the surface soil horizons, but little information is available regarding the effect of the removal of crop residues by burning. This study aimed to assess the impact of different types of crop residue management practices on the total C distribution and natural abundance of 13C (‰, δ13C). Two volcanic soils, located in the Mediterranean temperate zone of Southern Chile, were studied: an Ultisol (Collipulli Series, CPL) and an Andisol (Santa Barbara Series, SBA). Both soils had been cultivated under direct-drilling and a typical annual crop rotation system for a long period of time. Two different types of crop residue management practices were imposed in both soils: (i) crop residue burning (CPL-B; SBA-B) and (ii) crop residue retention over the soil (CPL-R; SBA-R), corresponding to treatments B and R, respectively. Soil profile distribution of the...

Despite annual legume pasture are of great importance for dryland agricultural systems in Mediterranean environments, there are few studies of N2 biological fixation (NBF) reported in Chile. In this study the NBF of four annual legume species: subterranean clover (Trifolium subterraneum L.), yellow serradella (Ornithopus compressus L.), arrow-leaf clover (T. vesiculosum L.), and crimson clover (T. incarnatum L.) (Experiment 1), as well as seven mixtures of these species (Experiment 2) were assessed. The NBF was measured by the 15 N natural abundance technique. The objective was to determine NBF in the legume species and in distinct mixtures used. The study was carried out in an Andisol of the Andean Precordillera located in the humid Mediterranean zone of Chile. Pasture was evaluated for biomass; and total N and natural abundance of 15 N were analyzed in plant material samples. In Experiment 1 (monospecific legume species pasture), N derived from fixation ranged between 43 and 147 kg N ha -1 and where T. vesiculosum and T. subterraneum presented statistical differences (P ≤ 0.05) in connection with the other species. In the legume mixtures (Experiment 2), N derived by fixation varied between 97 and 214 kg N ha -1 where the 50-50 mixtures (T. subterraneum and O. compressus, or T. subterraneum and T. vesiculosum, respectively) had the highest N fixation. Fixed N ranged between 12 and 25 kg N t -1 DM, showing significant differences among mono and polyspecific legume species.