Soil structure degradation in patches of alfalfa fields

Abstract

Alfalfa (Medicago sativa) is the basic forage resource for milk production in the flat Pampa of the Santa Fe Province of Argentina. However, the presence of microrelief with patches threatens the expansion of the area cultivated with alfalfa. The lower productivity in the patches is attributed to the inferior soil physical quality. The objectives of this study were to quantify indicators of soil physical quality and to establish the soil properties that would affect the alfalfa productivity in patches (PA) and normal areas (NA). Additionally, the macro and micro nutrient contents in both areas were determined. The experiment was carried out on an Aquic Argiudoll. Eighteen sampling sites, nine in NA and nine in PA were established. At each site, undisturbed soil samples (5 × 5 cm cores) were collected to measure soil bulk density (Bd), soil resistance to root penetration (PR), effective stress (σ), the water release curve and the least limiting water range (LLWR). Disturbed soil samples were also taken to determine macro and micronutrient contents, and particle size distribution. Non differences were detected for soil chemical properties between PA and NA. Aggregate size distribution indicated predominance of small aggregates in PA. Bd, PR and s were higher in PA than in NA, while the LLWR was narrower. Inadequate aeration under conditions of excessive soil moisture and inappropriate soil mechanical resistance when the soil is dry would affect alfalfa productivity. The overall results indicate that the soil physical quality in PA is lower than in NA.

Soil physical quality of Mollisols quantified by a global index

“…When analyzing air capacity (AC t ) corresponding to pores with diameters more than 30-µm diameter, the low values observed, especially in the B horizon, indicated evidence of the difficulties of these soils in terms of fluid flows. This indicator suggests the existence of reduced air volume to be used after heavy rainfall and confirms aeration problems found in different studies in the least limiting water range (Damiano and Moschini, 2011;Miretti et al, 2010).…”

Screening of weeds and their effect on alfalfa (Medicago sativa)

“…In general, after about three years alfalfa cannot maintain its original plant stand and growth, resulting in substantial loss in seed and hay yield, due to weed invasion and depletion of soil fertility (Malhi 2011, Entz et al 1995. Inadequate aeration under excessive soil moisture and inappropriate soil mechanical resistance in dry soil can also affect alfalfa productivity (Miretti et al 2010). Hence, some macronutrients such as phosphorus (P), sulfur (S), potassium (K) and some micronutrients, such as boron (B) become very concentrated (Malhi 2011).…”

Field Phenotyping and Long-Term Platforms to Characterise How Crop Genotypes Interact with Soil Processes and the Environment

“…The characteristics of organic agricultural systems in comparison to conventional systems have been extensively reviewed elsewhere [122], but, briefly, these include a range of potential benefits, such as biodiversity at soil, crop, field and landscape level and the greater focus on integration of crop and livestock production systems on the farm compared with conventional farming systems [136]. The greater biodiversity of organic farms is thought to provide a range of ecosystem services that enhance farm resilience to a large extent and reduce environmental impact [137,138], although there are some pedoclimatological conditions when the organic systems have negative environmental impacts such as on steep slopes [138]. Moreover, the benefits of organic agriculture vs. conventional agriculture are sometimes questioned due to issues associated with reduced output and therefore carrying capacity of the agricultural system and the potential impact on food security, along with inappropriate use of organic inputs leading to point source pollution of the environment [139].…”