Soil quality indicators in Vertisols under sugarcane

Maintaining or improving soil quality is crucial for agricultural productivity. This study was undertaken on the north coast of Cuba with the objective to select soil quality indicators to characterise Vertisols. For the selection of soil quality indicators, we have conducted four field experiments where organic fertilisers (sugarcane filter cake, compost) and natural minerals (dolomite, zeolite) were applied. Sugarcane (Saccharum officinarum L.) was used in all experiments. Soil properties were determined such as the amount of water-stable aggregates, permeability, plastic limit, pH in water, pH in KCl, organic matter, P₂O₅ and K₂O. The sugarcane yield components such as cane yield (t ha^?1) and sucrose yield (t ha^?1) were evaluated. Principal components analysis and simple regression analysis were also performed. Both organic matter and water-stable aggregates were closely related to cane yield, with r values of 0.87–0.97. The properties with best responses to treatments over time were permeability, water-stable aggregates, degree of soil aggregation and organic matter; therefore, they can be considered as soil quality indicators for the studied Vertisols.     

Influence of Aggregate Size,Electrolyte Concentration,and Sodium Adsorption Ratio on Crack Parameters of a Vertisol

Shrinking–swelling and crack formation influence soil physical behavior and productivity. Soil factors affecting crack formation and dimensions are clay content and mineralogy, aggregate stability as well as total concentration (C_t), and sodium adsorption ratio (SAR) of soil solution. Tillage intensity, which determines aggregate size, may also play a significant role in crack formation and dimensions. In the present work, total length, mean width, total area, and cover percentage of cracks were studied, under laboratory conditions, in beds of two aggregate sizes (<1 and 2–1 mm) of a Vertisol. The beds were saturated, equilibrated with sodium chloride (NaCl)/calcium chloride (CaCl₂) solutions of C_t 2, 5, 10, 20, and 30 mmol/L and SARs 0, 2, 5, 10, and 20 (mmol/L)^1/2, and allowed to air‐dry. After air‐drying, pictures of the samples were taken and used for the calculation of crack parameters by a scanning program. The results showed that aggregate size was the dominant factor determining the crack parameters: the cracks formed in beds of aggregates <1 mm were wider and of a smaller total length, total area, and cover percentage (p < 0.05) than those cracks formed in beds of aggregates 2–1 mm in size. It was also determined that changes of C_t resulted in a greater influence on crack characteristics than changes of SAR in the equilibrating solutions.     

A new method for studying clay soils using unaltered soil blocks

The purpose of this paper is to outline a procedure for soil block extraction, which is highly appropriate for clay soils. The method described here is rapid and cheap and has been used successfully by us in clay soils in southern Spain for the last six years. A wooden box is used to shape the soil block in situ and protect it during its transport from the field to the laboratory. Polyurethane foam was selected as the bonding agent, between the wooden framework and the soil block in order to avoid any possible alterations of the soil. This type of foam is used because it is strong, durable and non-toxic. The polyurethane foam is applied to the soil block as a permanent coating. This technique allows us to extract the clay soil solution in the laboratory.     

淮北变性土区玉米施用硫·锌微肥的效果

试验结果表明 ,在淮北变性土区 ,施用硫、锌微肥能促进玉米植株的生长发育 ,增强玉米的抗旱能力 ,促进玉米果穗的生长发育和籽粒的灌浆 ,增加玉米籽粒产量     

Drainage,sowing date and variety effects on chickpea grown on a Vertisol in Ethiopia

A field experiment was conducted for three years at Ginchi in Ethiopia to study the effects of three drainage methods [broad-bed-and-furrow (BBF), ridge-and-furrow (RF) and flat beds (FB)] arranged as main plots. Sub-plots comprised a factorial combination of four sowing dates (18 and 31 August, and 14 and 28 September) and three Desi-type chickpea varieties (Worku, Akaki and a landrace) in a split-plot design with three replications. Improved drainage methods (BBF and RF) increased chickpea seed yield by an average of 45% over the flat seedbed. There was a quadratic relationship between seed yield and sowing date with a peak yield in mid-September. Improved varieties (Worku and Akaki) yielded 15–19% more than the local check. Improved varieties were significantly more yielding than the landrace variety under the improved drainage system but not under the flat bed system. Also, improved varieties yielded significantly more than the landrace variety in the first three sowing dates when waterlogging was a problem but not in the last sowing date after which drought stress normally sets in. Sowing of improved chickpea varieties in mid-September using BBF could markedly increase productivity of chickpea on Vertisols in Ethiopia.     

Changes in soil properties and soil solution nutrients due to conservation versus conventional tillage in Vertisols

Understanding of tillage effects on soil chemical properties and cations in soil solution dynamics is essential for making appropriate land-management decisions. Measurements were made after more than 25 years of different tillage treatments: conventional tillage (CT) and conservation tillage, which includes no-till (NT) and minimum tillage (MT). pH and bulk density did not show important changes but exchangeable cations and cations in soil solution were affected by depth and different tillage. The highest concentration of exchangeable Ca²⁺ and Mg²⁺ was found in NT, decreased in MT and the lowest concentration was found in CT (mean values were 26.0, 24.4 and 23.3 cmol_c kg^?1 for exchangeable Ca²⁺ and 4.2, 3.7 and 3.3 cmol_c kg^?1 for exchangeable Mg²⁺ in NT, MT and CT, respectively). In addition, the highest concentration of exchangeable Na⁺ was found in NT, decreased in CT and the lowest concentration was found in MT. However, the highest concentration of exchangeable K⁺ was found in MT. A significant depth effect was observed for cations in soil solution: Na⁺ increased with depth whereas K⁺ and Ca²⁺ decreased with depth. This study aims to demonstrate the effect of tillage on the distribution and concentration of certain chemical soil properties.     

Improved management of Vertisols in the semiarid tropics for increased productivity and soil carbon sequestration

Abstract. This study was undertaken to test the hypothesis that an improved system of catchment management in combination with appropriate cropping practices can sustain increased crop production and improve soil quality of Vertisols, compared with prevailing traditional farming practices. Initiated in 1976, the improved system consisted of integrated land management to conserve soil and water, with excess rainwater being removed in a controlled manner. This was combined with improved crop rotation (legume based) and integrated nutrient management. In the traditional system, sorghum or chickpea was grown in the post-rainy season with organic fertilizers, and in the rainy season the field was maintained as a cultivated fallow. The average grain yield of the improved system over 24 years was 4.7 t ha⁻¹ yr⁻¹, nearly a five-fold increase over the traditional system (about 1 t ha⁻¹ yr⁻¹). There was also evidence of increased organic C, total N and P, available N, P and K, microbial biomass C and N in the soil of the improved system. A positive relationship between soil available P and soil organic C suggested that application of P to Vertisols increased carbon sequestration by 7.4 t C ha⁻¹ and, in turn, the productivity of the legume-based system, thus ultimately enhancing soil quality.     

Assessment of the limiting nutrients for wheat (Triticum aestivum L.) growth using Diagnosis and Recommendation Integrated System (DRIS)

ABSTRACT

The Diagnosis and Recommendation Integrated System (DRIS) was used as a tool to assess the limiting nutrients for wheat growth. To this effect, two separate greenhouse experiments were conducted to assess the limiting nutrients for wheat growth using soil samples collected from Wolmera district, Ethiopia. The experiments consisted of eight fertilizer treatments, optimum (Opt.), optimum-N (Opt-N), optimum-P (Opt-P), optimum-K (Opt-K), optimum-S (Opt-S), optimum-B (Opt-B), optimum-Zn (Opt-Zn) and control on Nitisols and six fertilizer treatments (Opt, Opt-N, Opt-P, Opt-S, Opt-B, and control) on Vertisols. In Nitisols, dry shoot weight yields were reduced by 93%, 70%, and 50% in the control, Opt-N, and Opt-P treatments, respectively. Whereas the corresponding reductions were 85%, 78%, and 42%, respectively, in Vertisols as compared to the optimum treatment. DRIS results indicated that N is the most limiting nutrient, followed by S, B, and P, while Zn was the least limiting nutrient for wheat production in the two study soils.     

Root aeration improves yield and water use efficiency of tomato in heavy clay and saline soils

Water logging and salinity of the soil alter both the physical and biological environment of plant roots. In two experiments, we investigated the effects of imposed aeration on yield and the physiological response of tomato (Lycopersicon esculentum L.) variety Improved Apollo growing under protected conditions over a range of salinities (the salinity experiment), and under constant field capacity (FC) or drier soil conditions (the moisture experiment). Subsurface irrigation with aerated water (12% air in water) stimulated above-ground growth, and enhanced the reproductive performance through earliness for flowering and fruiting compared with the control. Fruit yield of tomato with aeration in the moisture experiment was increased by 21% compared with the control (4.2 kg versus 3.7 kg per plant), and the effect of aeration on fruit yield was greater in FC than in the drier treatment. Fruit yield was increased by 38% in saline soil due to aeration compared with the non-aerated control. Increasing salinity from 2 to 8.8 dS m⁻¹, and 10 dS m⁻¹ reduced fruit yield by 18% and 62%, respectively, but 4 dS m⁻¹ did not suppress yield. Aeration in both the experiments increased plant water use and water use efficiency (WUE), expressed as weight per unit of applied water. Biomass WUE was greater by 16% and 32% in the moisture and salinity experiments, respectively. The increased yield with aeration was also accompanied by an increased harvest index (HI) defined as the proportion of dry fruit biomass to total dry biomass, greater mean fruit weight, high fruit DM, and increase in leaf chlorophyll content and shoot: root ratio, and a reduced water stress index (computed from the difference between air and leaf temperature). The benefit gained from aerating irrigation water was not only observed under conditions where air-filled porosity may be low (e.g., in poorly structure sodic soils, or at field capacity in clay soils), but also in drier soils.     

Particulate organic matter in water stable aggregates formed after the addition of C-labeled maize residues and wetting and drying cycles in vertisols

Development of soil structure and the dynamics of water stable aggregates (WSA) in many soils are known to be closely related to the cycling of soil organic matter. In some fine and medium textured soils particulate organic matter (POM) has been found to act as a nucleus for macroaggregate formation. However, this role of POM in aggregate formation has not been demonstrated in soils dominated by smectitic clay minerals. This study explored aggregation processes in a Vertisol from a semi-arid region in Northeastern Mexico in relation to the addition of ¹⁴C-labeled maize residues and application of wetting and drying cycles during 105 days of incubation. Fractionation of the WSA formed showed that labeled residues were preferentially accumulated in large macroaggregates (>2000 μm). Treatments with addition of organic residues had three to four times more intra-aggregate particulate organic matter (iPOM) in large macroaggregates than the control after 14 days of incubation. Residue-derived carbon accounted for 53% and 41% of the total carbon stored in the iPOM fraction in amended treatments with and without wetting and drying cycles, respectively. Conversely, residue-derived carbon represented <20% of the total carbon in the iPOM fraction from small macroaggregates (250-2000 μm) and microaggregates (53-250 μm). Results also showed that the amount and concentration of carbon per large macroaggregate did not differ between the large macroaggregates formed under wetting and drying and those formed in continuous moist conditions. However, due to formation of higher number of large macroaggregates per kg of soil, more carbon could be stored in amended soils under wetting and drying than in constantly wet soil: 1.4, 1.8 and 2.7 times more ¹⁴C kg⁻¹ soil after 14, 58 and 105 incubation days, respectively. The results in this study suggest that wetting and drying enhanced protection of the added maize residues inside large macroaggregates by forming more aggregates, rather than by increasing the amount of POM entrapped per aggregate. Therefore, after the addition of organic residues, this soil could accumulate more C than continuous moist soil through the influence that wetting and drying has on soil aggregation.