A Contribution to Soil Fertility Assessment for Arid and Semi-Arid Lands

Soil fertility must be viewed as a dynamic concept that involves the constant cycling of nutrients between organic and inorganic forms. In this context, it refers also to supply adequate amounts of water and aeration for plant growth. Soil fertility under arid and semi-arid lands is constrained not only by limited water availability but also by small organic matter contents. Most fertility assessment systems are based on organic matter contents as the main parameter. However, crop experiments from various irrigated arid and semi-arid soils indicate that productivity is less- affected by organic matter contents than assumed. Therefore, we propose a new soil fertility system for dryland soils. It is a rule-based set of algorithms, mainly using additions and subtractions. Soil, climate, and landscape factors are integrated to calculate the numerical value of fertility for a given soil. We expect the system, which is focused on soil properties that keep or increase optimum soil moisture (such as texture), to be applicable in arid and semi-arid lands and to provide more realistic estimates of fertility regarding agricultural purposes. The manuscript will provide an outline of the main aspects of the system, illustrated by various case applications.

Contested Grasslands: Commons and the Unequal Land-Costs to Sustain Soil Fertility in Preindustrial Agriculture

Maintaining soil fertility was the most pressing problem in preindustrial agriculture. Prior to the arrival of industrial inputs, farmers relied on ecological soil replenishment processes and biological fertilizing techniques to sustain the productivity of soil. Central European farmers actively managed the cycling of nutrients by keeping livestock. Farm animals provided the means to recycle nutrients from crop production and to transfer nutrients from land-use systems dedicated for biomass extraction, such as grasslands. This article explores the unequal distribution of these vital resources in the Manor Bruck, Austria, and its impact on landlord’s and peasant’s abilities to meet the “land costs” of sustaining soil fertility. The article tests the hypothesis as to whether inequality was a major driver for unsustainable farming practices and the degradation of agro-ecosystems in the long run. Focal points are commons and communal land-use systems and their role in cycling nutrients through the agricultural landscape. Commons in the Manor Bruck comprised vast grasslands, which provided an important ecological buffer to balance the continuous export of nutrients from crop production for all actors. The aim is to demonstrate how social conflict emerging from the competition over commons guides us to the specific sustainability challenges faced by farmers.

CYCLING OF WINTER FORAGE NUTRIENTS UNDER INTEGRATED CROP-LIVESTOCK SYSTEMS

This study aimed to evaluate the decomposition and release of nutrients from the remaining straw of two annual forage species conducted in an integrated crop-livestock system (ICLS). The experimental design used was randomized blocks, in split plots, with three replicates. The managements were allocated in the plots (52 m2): without grazing, one grazing, and two grazings. Subplots were defined by material collection times after the forage’s desiccation (0, 30, 60, 90, and 120 days after desiccation). Dry matter yield, amounts of carbon, nitrogen, phosphorus, and potassium, and half-life time were evaluated. Oat cultivar IPR Esmeralda had the highest initial dry matter yield (6,099 kg ha-1) when not grazed, while triticale cultivar IPR 111 showed the highest average values when subjected to grazing (8,088 kg ha-1). The amounts of N, P, and K released from the remaining dry matter, regardless of the management adopted, decreased over time. Potassium was the nutrient that presented the most accelerated release, with an average half-life of 14 days. When subjected to grazing, triticale is more efficient in nutrient cycling, providing 197, 38, and 231 kg ha-1 of N, P, and K, respectively, with a half-life time of 10, 37, and 25 days, respectively. Forage species can improve the cycling of nutrients and make them available to crops in succession in the ICLS.

Dynamics of leaf, flower and fruit abscission in avocado cv. Hass in Antioquia, Colombia

The amount of leaf litter produced by avocado trees cv. Hass is an important potential source of mineral resources, and quantifying its production and nature is crucial to understanding the cycling of nutrients. The main objective of this study was to quantify the production of leaf litter and fallen flowers and small fruits in avocado orchards at eight locations in three producing areas in the Department of Antioquia (west, southwest, and north). The highest leaf litter production occurred in southwest Antioquia, at Jardin (7.6 t ha-1 year-1); the east locations had similar leaf fall (4.03-3.4 t ha-1 year-1). The dry matter produced in the north was very similar in both locations. The dry matter was 2.8 t ha-1 year-1. Higher leaf litter was recorded in all locations during the driest periods. Approximately 80% of the fallen fruits had diameters less than 1 cm. The highest flower production and fall occurred in southwest Antioquia, followed by the northern region.

LEAF CONTENTS AND BIOCHEMICAL CYCING OF NUTRIENTS IN ACCESSIONS OF UMBU AND UMBU-CAJA

ABSTRACT Information is needed on the characteristics of potential accessions of Spondias tuberosa Arruda Câmara (umbu) and Spondias sp.(umbu-caja) for commercial planting and preservation. Thus, the objective was to evaluate the leaf contents and cycling of nutrients of 15 accessions of umbu and one of umbu -caja. The treatments consisted of 16 accessions: BGU-44, BGU-45, BGU-47, BGU-48, BGU-50, BGU-75, EPAMIG-01, EPAMIG-03, EPAMIG-04, EPAMIG-05, EPAMIG-06, EPAMIG-07, EPAMIG-09, EPAMIG-13, umbu of unknown origin and the umbu-caja Princesa. A completely randomized experimental design was adopted, with three replicates, consisting of one plant each. Nutrient contents in the leaves were measured in the leaf flushing and leaf senescence phases in the 2015/2016 and 2016/2017 seasons, and the N, P, K and Mg retranslocation rates were determined. The accessions showed average leaf nutrient contents of 28.6, 27.6, 9.5, 4.20, 2.5 and 2.0 g kg-1 with the descending order N>Ca>K>Mg>S>P, respectively, and 103.61, 86.22, 82.12, 60.2, 16.0 and 3.52 mg kg-1 of Fe>B>Na>Mn>Zn>Cu, respectively. The accession BGU-48 had higher N and P retranslocation efficiency in the leaves and BGU-50 showed recycling efficiency for K and Mg. The order of retranslocation rates is K>P>N>Mg, being higher in the 2015/2016 season.

Managing Soils for Recovering from the COVID-19 Pandemic

The COVID-19 pandemic has disrupted the global food supply chain and exacerbated the problem of food and nutritional insecurity. Here we outline soil strategies to strengthen local food production systems, enhance their resilience, and create a circular economy focused on soil restoration through carbon sequestration, on-farm cycling of nutrients, minimizing environmental pollution, and contamination of food. Smart web-based geospatial decision support systems (S-DSSs) for land use planning and management is a useful tool for sustainable development. Forensic soil science can also contribute to cold case investigations, both in providing intelligence and evidence in court and in ascertaining the provenance and safety of food products. Soil can be used for the safe disposal of medical waste, but increased understanding is needed on the transfer of virus through pedosphere processes. Strengthening communication between soil scientists and policy makers and improving distance learning techniques are critical for the post-COVID restoration.

Feeding the reactors: potentials in re-cycled organic fertilisers

There is a large and growing interest in producing proteins, oils and other important commodities in bioreactors. Mineral fertilisers, especially nitrogen (N) and phosphorus (P), are used to supply the living organisms with nutrients, and for growing of fungi, carbon must be applied from sugar or starch products. This input-for-output approach does not contribute to cycling of nutrients and organic matter in the society. Organic*1 agriculture has a strong interest in recycled fertilisers and best utilisation of organic materials, and appliccable products should be developed not only for use in agricultural fields but also for other purposes, such as hydroponics, aquaponics and bioreactors. Animal bones and precipitated struvite from waste water are examples of materials which may be applicable in bioreactors. Containing easily available N and P, recent studies have shown that these materials are valuable for amendment of soil fertility and crop productivity in land-based agriculture. Studies should be initiated to design bioreactors utilising locally available sources of nutrients and organic matter, to make the bioreactors more sustainable and develop organic* farming systems in a context of landless farming.