Suboptimal Soil Research Articles

Scion–rootstock interactions influence the growth and behaviour of the grapevine root system in a heavy clay soil

Background and Aims Generally, grapevine roots have been less studied than the above-ground parts of the plant. Here we analyse scion–rootstock interactions in mature vines growing in a heavy clay soil in a climate characterised by severe summer drought to investigate the effect of the scion–rootstock interaction in a suboptimal soil. Methods and Results The rootstocks, 34 Ecole de Montpellier, 140 Ruggeri and 1103 Paulsen, were grafted onto Nerello Mascalese and Nero d'Avola scions and assessed along with self-rooted vines. Root distribution and root architecture were analysed using the profile wall method at 0, 60 and 120 cm from the row midline. Root density was greatest at a depth between 21 and 60 cm. The cumulative root fraction for root density registered a β value, a numerical quantity that summarises depth distribution, ranging between 0.932 and 0.962. Root number and density were significantly lower for the self-rooted vines compared to that of the grafted vines. Conclusions The scion genotypes affected most developmental parameters, including the diameter of the root system, the root density at 21–80 cm depth and the ratio of fine roots to coarse roots. Significance of the Study The scion plays an important role in grapevine root growth, development and distribution in a heavy clay soil, although the mechanism remains unclear.

UTILIZATION OF SUGARCANE FILTER PRESS MUD AS ORGANIC FERTILIZER FOR IMPROVING CHEMICAL PROPERTIES OF ULTISOLS AND OIL PALM SEEDLINGS

<p>Ultisols is suboptimal soil that have many problems those are low pH, nutrient deficiency and micronutrient toxicity and inhibit for crop growth and need ameliorant for improving the soil fertility. The aim of this research were to investigate the utilization of filter press mud compost for improving chemical properties of Ultisols and growth of oil palm seedling. This research consisted of five levels of compost (A=without compost, B= 4.25 t.ha<sup>-1</sup>,C=8.5 t.ha<sup>-1</sup>, D=12.75 t.ha<sup>-1</sup> and E=17 t.ha<sup>-1</sup>) with three replications. The treatment units were allocated based on Randomized Block Design. The addition of filter press mud compost improving chemical properties of Ultisols especially pH value, decreasing Aluminum, total N 0.45%, organic C 2.19%, available P 37.14 ppm, CEC 22.04 cmol.kg<sup>-1. </sup>Filter press mud compost increased growth of oil palm seedling. Application of 12.75 t.ha<sup>-1 </sup>gave the optimum growth of oil palm seedlings. It showed that the crop height increased by 51.56%, leaves by 47.63%, N content by 2.26 %, P content by 0.18 % and K content by 1.44 %.</p>

Improving productivity and increasing the efficiency of soil nutrient management on grassland farms in the UK and Ireland using precision agriculture technology

Abstract Grass growth and utilisation on grassland farms across the UK and Ireland are below their potential, and nutrient management is sub-optimal. Excessive soil phosphorus concentrations are an issue, contributing to eutrophication of waterways, while sub-optimal soil pH due to a reduction in lime use is seen in many areas. This paper discusses the potential for introducing technology onto grassland farms, and implementing sensible farm-specific management decisions as a means of enhancing productivity and minimising the environmental impact of livestock farming. The adoption rate of Precision Agriculture (PA) technology by grassland farmers in the UK and Ireland is still relatively low, and significantly lagging behind the advances that have taken place within the arable farming community. With rapidly advancing technology and investment in research, there are now a range of soil sensors available along with technology for grass growth monitoring, yield mapping, remote sensing, satellite imagery, and devices for tracking animal movement, behaviour and feed intake. In this review paper we examine the latest technology developments specific to grassland farming and we question their suitability and ‘readiness’ for adoption by farmers. The review identifies the challenges that are specific to grassland such as complex soil, vegetation and climatic variables along with economic barriers that may be preventing change within the farming community in these areas.

TITONIA DAN JERAMI PADI YANG DIKOMPOSKAN TERHADAP CIRI KIMIA TANAH DAN PRODUKSI JAGUNG PADA ULTISOL

Ultisol is broad suboptimal soils, need to be developed to increase for foods and animal feeds, but properties of physics and chemistry by the soils bad. This research was aimed to studied the influence of compost derived from titonia plus rice straw in improving chemical properties of Ultisol and corn production. This researh was conducted in glasshouse and Soil Laboratory of Agriculture Faculty, Andalas University, Padang, West Sumatra, Indonesia from January to July 2017. The experiment consisted of 5 treatments (0.00; 2.50; 5.00;7.50; 10.00 tonha-1. with 3 replications. Soil data resulted were compared to the soil criteria, while corn data were statistically analyzed the variance and continued using DNMRT at 0.05 level of significance, if F-calculated > F-table. The results of research showed that optimum dosage for repaired chemical properties of 7,50 tonha-1. It dosage soil pH 6,18 unit; available P by 17,64ppm; CEC by 18,38cmol(kg)-1; organic-C by 1,27%, total-N by 0,23%; K-exch. by 0,49cmol(kg)-1; Ca-exch. by 2,63 cmol(kg)-1; Mg-exch. by 0,57cmol(kg)-1 dan Na-exch. by 0,39cmol(kg)-1, with dry weight of seed by 85,48gpot-1; dry weight of straw by 75,84gpot-1 and dry weight of 100 seed by 25,50g. Key words : Compost derived from titonia plus rice straw, corn, Ultisol.

Castor seed yield at suboptimal soil moisture: Is it high enough?

This study discusses how soil moisture influences the seed yield of two castor plant varieties in an arid zone in Mexico. An experiment was set up with two factors: soil moisture, with three levels (high = -0.05 MPa, medium = -0.31 MPa and low = -0.91 MPa), and castor variety (Krishna and Rincon). The combination resulted in a factorial 3 × 2 experimental design. The experiment was set up as a randomized block with four replications under a split-plot arrangement, where the whole plots were for soil moisture and the subplots were for the castor variety. The measured variables were plant height (PH), days to flowering of 50% of the plants (DF), leaf area (LA), dry weight (DW), source-sink relationship, harvest index (HI) and seed yield. Data were analyzed by ANOVA, mean tests (HSD at α = 0.05) and regression analysis. There were significant differences in PH, LA, DW, HI and yield among the treatments. The values of PH, LA and DW tended to be higher at higher soil moisture levels than at lower moisture levels. The source strength was generally lower than the sink strength in all the treatments. There were significant differences between the varieties for HI, and the interaction between soil moisture and variety was also significant. Significant differences were found in yield; the Krishna variety had a greater yield than the Rincon variety, but there was only a significant difference between the yield of the Krishna variety cultivated under low soil moisture (5200 kg ha-1) and that of the Rincon variety cultivated under high soil moisture (2570 kg ha-1). The results of this study indicate that castor plants can be cultivated in arid regions at suboptimal soil moisture levels with supplementary irrigation without compromising plant performance or yield.

Abiotic stresses in olive: physiological and molecular mechanisms

Olive (Olea europaea L.) cultivation in traditional Mediterranean agro-ecosystems and in newly cultivated areas of the world (North and South America, Australia, New Zealand and South Africa) regularly undergoes climatic constraints and suboptimal soil conditions that impair olive physiology and, ultimately, plant productivity. Of abiotic stresses, drought, suboptimal temperatures, salinity and nutrient deficiencies are those that are most relevant. Since abiotic stress symptoms are not immediately recognized in the field, their negative effects on both yield and quality very often become economically relevant. In this article, the state of the art of research aimed at understanding the physiological and molecular mechanisms activated by drought, salinity and suboptimal temperatures is reviewed.

Functionality of Root-Associated Bacteria along a Salt Marsh Primary Succession.

Plant-associated bacteria are known for their high functional trait diversity, from which many are likely to play a role in primary and secondary succession, facilitating plant establishment in suboptimal soils conditions. Here we used an undisturbed salt marsh chronosequence that represents over 100 years of soil development to assess how the functional traits of plant associated bacteria respond to soil type, plant species and plant compartment. We isolated and characterized 808 bacterial colonies from the rhizosphere soil and root endosphere of two salt marsh plants, Limonium vulgare and Artemisia maritima, along the chronosequence. From these, a set of 59 strains (with unique BOX-PCR patterns, 16S rRNA sequence and unique to one of the treatments) were further screened for their plant growth promoting traits (siderophore production, IAA production, exoprotease production and biofilm formation), traits associated with bacterial fitness (antibiotic and abiotic stress resistance – pH, osmotic and oxidative stress, and salinity) and metabolic potential. An overall view of functional diversity (multivariate analysis) indicated that the distributional pattern of bacterial functional traits was driven by soil type. Samples from the late succession (Stage 105 year) showed the most restricted distribution, harboring strains with relatively low functionalities, whereas the isolates from intermediate stage (35 year) showed a broad functional profiles. However, strains with high trait performance were largely from stage 65 year. Grouping the traits according to category revealed that the functionality of plant endophytes did not vary along the succession, thus being driven by plant rather than soil type. In opposition, the functionality of rhizosphere isolates responded strongly to variations in soil type as observed for antibiotic resistance (P = 0.014). Specifically, certain Pseudomonas sp. and Serratia sp. strains revealed high resistance against abiotic stress and antibiotics and produce more siderophores, confirming the high plant-growth promoting activity of these two genera. Overall, this study contributes to a better understanding of the functional diversity and adaptation of the microbiome at typical salt marsh plant species across soil types. Specifically, soil type was influential only in the rhizosphere but not on the endosphere, indicating a strong plant-driven effect on the functionality of endophytes.

Soil Heating and Secondary Plant Covers Influence Growth and Yield of Winter High Tunnel Spinach

High tunnel (HT) winter production may be limited by extreme low air temperatures, suboptimal soil temperatures, large diurnal temperature changes, and short daylengths and associated low light conditions. To determine the productivity of spinach in extreme climates, HT production trials were conducted in the fall (October to December) and winter (January to March) of 2010–12 at the Greenville Research Farm in Logan, UT (lat. 41 N. elevation 1455 m). Soil heating (±) using electric cables and secondary covers (fabric rowcovers and plastic low tunnels) were evaluated to determine combined effects on fall and winter spinach production. Soil heating significantly increased yield in all cover treatments in the Fall 2010 (F2010) trial when spinach was planted in November, but had little to no effect on plant productivity in the other three trials (more appropriate planting dates) even though it did increase soil temperature marginally. The addition of secondary covers significantly increased plant biomass and leaf area when compared with the uncovered control. Excluding the F2011 trial when spinach was planted earlier under more favorable temperature and light conditions, the use of low tunnels resulted in significantly higher spinach yields (biomass and leaf area) than when grown under fabric rowcover. In the fall, relative growth rates (RGRs) decreased exponentially regardless of whether the soil was heated or not heated or if a secondary cover was used. This response was because of the seasonal decline in light levels and temperatures. In the winter production cycle, spinach relative growth without covers was similar or increased as climatic conditions improved. For plants grown under fabric or plastic rowcovers, RGR remained more constant or decreased during the production cycle. Increased yields were possible with secondary covers as air temperatures increase more quickly in the morning, maintained optimal temperatures longer each day (higher growing degree hours), and retained trapped heat later into the evening. Statistical interaction between heating cables and secondary covers were rarely observed. Fall and winter HT spinach production increases when further protection with secondary plant covers is provided; however, supplemental soil heating is not necessary.

Does triacylglycerol (TAG) serve a photoprotective function in plant leaves? An examination of leaf lipids under shading and drought.

Plant survival in many ecosystems requires tolerance of large radiation loads, unreliable water supply and suboptimal soil fertility. We hypothesized that increased production of neutral lipids (triacylglycerols, TAGs) in plant leaves is a mechanism for dissipating excess radiation energy. In a greenhouse experiment, we combined drought and shade treatments and examined responses among four species differing in life form, habitat, and drought- and shade-tolerance. We also present a lipid extraction protocol suitable for sclerophyllous leaves of native Australian trees (e.g. Acacia, Eucalyptus). Fluorescence measurements indicated that plants exposed to full sunlight experienced mild photoinhibition during our experiment. Accumulation of TAGs did not follow photosynthetic capacity, but instead, TAG concentration increased with non-photochemical quenching. This suggests that plants under oxidative stress may increase biosynthesis of TAGs. Moderate drought stress resulted in a 60% reduction in TAG concentration in wheat (Triticum aestivum). Shading had no effect on TAGs, but increased concentrations of polar lipids in leaves; for example, acclimation to shade in Austrodanthonia spp., a native Australian grass, resulted in a 60% increase in associated polar lipids and higher foliar chlorophyll concentrations. Shading also reduced the digalactosyldiacylglycerol:monogalactosyldiacylglycerol (DGDG:MGDG) ratio in leaves, with a corresponding increase in the degree of unsaturation and thus fluidity of thylakoid membranes of chloroplasts. Our results suggest that prevention of photodamage may be coordinated with accumulation of TAGs, although further research is required to determine if TAGs serve a photoprotective function in plant leaves.

Applying 'drought' to potted plants by maintaining suboptimal soil moisture improves plant water relations.

Pot-based phenotyping of drought response sometimes maintains suboptimal soil water content by applying high-frequency deficit irrigation (HFDI). We examined the effect of this treatment on water and abscisic acid (ABA) relations of two species (Helianthus annuus and Populus nigra). Suboptimal soil water content was maintained by frequent irrigation, and compared with the effects of withholding water and with adequate irrigation. At the same average whole-pot soil moisture, frequent irrigation resulted in larger soil water content gradients, lower root and xylem ABA concentrations ([X-ABA]), along with higher transpiration rates or stomatal conductance, compared with plants from which water was withheld. [X-ABA] was not uniquely related to transpiration rate or stomatal conductance, as frequently irrigated plants showed partial stomatal closure compared with well-watered controls, without differing in [X-ABA] and, in H. annuus, [ABA]leaf. In two P. nigra genotypes differing in leaf area, the ratio between leaf area and root weight in the upper soil layer influenced the soil water content of this layer. Maintaining suboptimal soil water content alters water relations, which might become dependent on root distribution and leaf area, which influences soil water content gradients. Thus genotypic variation in 'drought tolerance' derived from phenotyping platforms must be carefully interpreted.

Rainwater, soil and nutrients conservation for improving productivity of citrus orchards in a drought prone region

The abundant surface runoff along with top fertile soil in rainy season, followed by sub-optimal soil water content (SWC) in root zone of the plants during post-rainy period is one of the major causes of low productivity and decline of citrus orchards in tropics. Keeping this in view, a study was conducted for seven years to evaluate the effects of different rainwater conservation techniques (RCTs) on runoff, soil and nutrients losses and yield of citrus orchard in Vertisols under a sub-humid tropical climate of central India. The RCTs: staggered trench (ST) and continuous trench (CT) with and without grass mulch (GM) were imposed in runoff plots (350m2 area) with 14 citrus plants across the slope (12%) and their performances were compared with without conservation measure (WCM) treatment. All the RCTs were effective in conserving rainwater, soil and nutrients (N, P, K, Fe, Mn, Cu and Zn), which imparted a favourable response on vegetative growth, leaf nutrient content, fruit yield and fruit quality of citrus plants. However, CT+GM produced the best response, conserving 49% runoff and 51% soil compared with WCM in the orchard. The available nutrients and organic carbon content in soil were significantly improved in mulched plots. The runoff generated made linear relations (R2=0.82–0.91) with rainfall amount in treated plots, whereas this relationship was exponential (R2=0.89) in WCM plot. However, the quantity of runoff made the linear relations with soil loss in both treated plots (R2=0.76–0.89) and WCM (R2=0.93). The rates of transpiration, photosynthesis and stomatal conductance of leaf and leaf water use efficiency of the citrus plants were higher under higher available SWC in CT+GM. The CT+GM produced 65% higher fruit yield with better quality fruits (higher juice content, TSS and ascorbic acid content with lower acidity) using 32% less irrigation water, resulting in 65% improvement in rainwater productivity and 143% improvement in irrigation water productivity compared with WCM. Citrus production with CT+GM was also found economically superior to other treatments, generating more annual net income (INR 125480ha−1) with higher benefit-cost ratio (3.1). Overall results of this study demonstrates that the conjunctive use of CT and GM could conserve substantial rainfall runoff, soil and nutrients, resulting higher yield and water productivity using less irrigation water in citrus orchard in clay soil.

Endophytic fungal diversity of Fragaria vesca, a crop wild relative of strawberry, along environmental gradients within a small geographical area.

BackgroundFungal endophytes are highly diverse ubiquitous asymptomatic microorganisms, some of which appear to be symbiotic. Depending on abiotic conditions and genotype of the plant, the diversity of endophytes may confer fitness benefits to plant communities.MethodsWe studied a crop wild relative (CWR) of strawberry, along environmental gradients with a view to understand the cultivable root-derived endophytic fungi that can be evaluated for promoting growth and tolerating stress in selected plant groups. The main objectives were to understand whether: (a) suboptimal soil types are drivers for fungal distribution and diversity; (b) high pH and poor nutrient availability lead to fungal-plant associations that help deliver fitness benefits; and (c) novel fungi can be identified for their use in improving plant growth, and alleviate stress in diverse crops.ResultsThe study revealed that habitats with high pH and low nutrient availability have higher fungal diversity, with more rare fungi isolated from locations with chalky soil. Plants from location G were the healthiest even though soil from this location was the poorest in nutrients. Study of environmental gradients, especially extreme habitat types, may help understand the root zone fungal diversity of different functional classes. Two small in vitro pilot studies conducted with two isolates showed that endophytic fungi from suboptimal habitats can promote plant growth and fitness benefits in selected plant groups.DiscussionTargeting native plants and crop wild relatives for research offers opportunities to unearth diverse functional groups of root-derived endophytic fungi that are beneficial for crops.

Seed Priming with Polyethylene Glycol Induces Physiological Changes in Sorghum (Sorghum bicolor L. Moench) Seedlings under Suboptimal Soil Moisture Environments.

Osmopriming with PEG has potential to improve seed germination, seedling emergence, and establishment, especially under stress conditions. This research investigated germination performance, seedling establishment, and effects of osmopriming with PEG on physiology in sorghum seedlings and their association with post-priming stress tolerance under various soil moisture stress conditions. Results showed that seed priming increased the environmental range suitable for sorghum germination and has potential to provide more uniform and synchronous emergence. Physiologically, seed priming strengthened the antioxidant activities of APX, CAT, POD, and SOD, as well as compatible solutes including free amino acid, reducing sugar, proline, soluble sugar, and soluble protein contents. As a result, seed priming reduced lipid peroxidation and stabilized the cell membrane, resulting in increased stress tolerance under drought or excessive soil moisture environments. Overall, results suggested that seed priming with PEG was effective in improving seed germination and seedling establishment of sorghum under adverse soil moisture conditions. Osmopriming effectively strengthened the antioxidant system and increased osmotic adjustment, likely resulting in increased stress tolerance.

Inhibition of tomato shoot growth by over‐irrigation is linked to nitrogen deficiency and ethylene

Although physiological effects of acute flooding have been well studied, chronic effects of suboptimal soil aeration caused by over-irrigation of containerized plants have not, despite its likely commercial significance. By automatically scheduling irrigation according to soil moisture thresholds, effects of over-irrigation on soil properties (oxygen concentration, temperature and moisture), leaf growth, gas exchange, phytohormone [abscisic acid (ABA) and ethylene] relations and nutrient status of tomato (Solanum lycopersicum Mill. cv. Ailsa Craig) were studied. Over-irrigation slowly increased soil moisture and decreased soil oxygen concentration by 4%. Soil temperature was approximately 1°C lower in the over-irrigated substrate. Over-irrigating tomato plants for 2 weeks significantly reduced shoot height (by 25%) and fresh weight and total leaf area (by 60-70%) compared with well-drained plants. Over-irrigation did not alter stomatal conductance, leaf water potential or foliar ABA concentrations, suggesting that growth inhibition was not hydraulically regulated or dependent on stomatal closure or changes in ABA. However, over-irrigation significantly increased foliar ethylene emission. Ethylene seemed to inhibit growth, as the partially ethylene-insensitive genotype Never ripe (Nr) was much less sensitive to over-irrigation than the wild type. Over-irrigation induced significant foliar nitrogen deficiency and daily supplementation of small volumes of 10 mM Ca(NO3 )2 to over-irrigated soil restored foliar nitrogen concentrations, ethylene emission and shoot fresh weight of over-irrigated plants to control levels. Thus reduced nitrogen uptake plays an important role in inhibiting growth of over-irrigated plants, in part by stimulating foliar ethylene emission.

Common and specific responses to availability of mineral nutrients and water.

Changes in resource (mineral nutrients and water) availability, due to their heterogeneous distribution in space and time, affect plant development. Plants need to sense these changes to optimize growth and biomass allocation by integrating root and shoot growth. Since a limited supply of water or nutrients can elicit similar physiological responses (the relative activation of root growth at the expense of shoot growth), similar underlying mechanisms may affect perception and acquisition of either nutrients or water. This review compares root and shoot responses to availability of different macronutrients and water. Attention is given to the roles of root-to-shoot signalling and shoot-to-root signalling, with regard to coordinating changes in root and shoot growth and development. Involvement of plant hormones in regulating physiological responses such as stomatal and hydraulic conductance is revealed by measuring the effects of resource availability on phytohormone concentrations in roots and shoots, and their flow between roots and shoots in xylem and phloem saps. More specific evidence can be obtained by measuring the physiological responses of genotypes with altered hormone responses or concentrations. We discuss the similarity and diversity of changes in shoot growth, allocation to root growth, and root architecture under changes in water, nitrate, and phosphorus availability, and the possible involvement of abscisic acid, indole-acetic acid, and cytokinin in their regulation. A better understanding of these mechanisms may contribute to better crop management for efficient use of these resources and to selecting crops for improved performance under suboptimal soil conditions.

Hydro-Priming of Seed Improves the Water Use Efficiency, Grain Yield and Net Economic Return of Wheat under Different Moisture Regimes

Wheat is the second most important staple food crop of India and contributes a major share to food basket of the country. Since majority of the area under wheat is irrigated, it consumes huge quantity of fresh water for its cultivation. The availability of good quality water for irrigation is decreasing over a period of time due to vagaries of monsoon, urbanization and industrialization. The biggest challenge on this front is to improve the efficiency and productivity of water being used in existing cropping system. Therefore, it is the need of hour to improve water use efficiency for wheat production. In the milieu, the present investigation was taken with an objective of studying the effect of pre-germinated seed in crop establishment under sub-optimal soil moisture conditions by using the residual soil moisture after harvesting of rice in Indo-Gangetic plains, so that pre sowing irrigation requirement for crop establishment may be cut and reduced in time period which require from pre-sowing irrigation to field preparation. This experiment was conducted for two consecutive years 2010-11 and 2011-12 to evaluate the influence of hydropriming on the water use efficiency and grain yield of wheat (Triticum aestivum L.) under moisture stress. The experiment was conducted in split plot design with three replications keeping moisture stress treatments (optimum moisture, sub-optimal moisture and dry soil followed by irrigation) in main plots and seed priming treatments (dry seed, hydropriming, and pre-germinated seeds) in subplots. Pregerminated seed produced significantly higher grain yield (5.49 t ha-1), which was statistically similar to hydropriming (5.30 t ha-1). Various seeding methods were statistically at par. The hydro-primed and pregerminated seeds established earlier than dry seeds leading to better crop establishment under optimum, sub optimum soil moisture as well as dry soil conditions leading to higher tillering and grain yield. The results of experiment showed that priming with plain water and pre-germinated seeds improved germination indices, seedling growth and crop establishment. Since priming with plain water and to have pregerminated seeds is simple and cheap method, which can increase germination percentage and homogeneity of seedling emergence under water stress conditions and it can be easily used by farmers. Interactive effect of different seed priming techniques along with seeding at sub optimal soil moisture level proved to be an efficient technique for enhancing water productivity of wheat crop. DOI: http://dx.doi.org/10.3329/sja.v11i2.18410 SAARC J. Agri., 11(2): 149-159 (2013)

Sustainable nutrient management at field, farm and regional level: Soil testing, nutrient budgets and the trade-off between lime application and greenhouse gas emissions

Pollution from agriculture has environmental consequences at local and global scales. Managing this pollution is challenging because of diffuse sources and complex relationships between aquatic and atmospheric emissions. We illustrate this for a UK county that has suffered outbreaks of microbial pollution and eutrophication. We surveyed 49 livestock farms covering 12% of total agricultural grazed land. Soil nutrient status and whole-farm nutrient balances were determined, and the environmental impact of alleviating sub-optimal soil pH by liming was estimated at the county level. Only 37% of fields contained more P than was required for satisfactory grass growth, and soil acidity and available K were often limiting production. The mean farm N, P and K balances were similar to a modelled farm in England & Wales and EU indicators for the majority of North West Europe. This suggests that local eutrophication events linked to agriculture are more likely to relate to improper timing of nutrient application rather than over-application. None of the surveyed farmers used nutrient decision support tools, largely due to a lack of awareness and competing sources of information. Liming soils to pH 6.0 was estimated to both reduce N-leaching and N2O emissions; however, the net climate-change impact would be negative as the direct CO2 emissions would exceed CO2 equivalent emissions of not liming by 394% (95% CI 201–21,232). Although liming currently presents a net cost to farmers, a sensitivity analysis suggests that reduced lime cost could lead to economic benefit to farmers but still increased greenhouse gas emissions. The results are applicable to all pasture-based agricultural systems where there is a drive to maintain or increase production through optimal soil and nutrient management. The findings demonstrate an important trade-off between reducing aquatic and atmospheric pollution and agricultural productivity, and the need to improve communication of this trade-off to farmers.

The effects of organic amendment and soil emplacement method on manufactured soil quality and growth of amenity woodland at a former cokeworks site

A trial was conducted to investigate soil manufacture strategies for restoration of a large industrial site to amenity woodland. Colliery shale soil-forming material was amended with two mixtures of organic waste products (a) 1:1 ratio municipal green waste compost to paper mill crumb and (b) 4:1 compost to paper crumb, to form subsoil profiles. The use of a loose tip method of soil emplacement was compared with (a) a conventional earthmover and (b) a wide track, low ground pressure earthmover. Growth of Quercus robur and Alnus glutinosa was not affected by the choice of organic amendment, but the addition of the 1:1 ratio organic amendment did result in significantly greater available nitrogen, phosphorus and potassium, CO2 evolution and moisture storage capacity than the 4:1 ratio amendment. The greater nutrient supply of paper mill crumb in this experiment demonstrates the importance of the specific composition of organic waste materials, which can result in significant variation in decomposition rate and nutrient release. The use of both organic amendments resulted in a soil profile capable of supporting woodland when best practice soil handling (loose tipping) was applied. The most appropriate ratio of organic material addition is dependent on end use nutrient requirements. Earthmover soil emplacement resulted in markedly greater penetration resistance, lower moisture storage, the generation of anaerobic conditions and inhibited growth of both Q. robur and A. glutinosa irrespective of the type of earthmover employed. The findings confirm the ability of Alnus species to establish relatively rapidly under sub-optimal soil conditions, although A. glutinosa was inhibited by poor rooting conditions in study years 3–4.

Managing declining yields from ageing tea plantations

Strong growth in the demand for tea requires further increases in the productivity of plantations. Declining or stagnant yields are commonly observed in older plantations. Possible controlling factors for yield decline are reviewed including ageing of plants, chronic disease and sub-optimal soil conditions such as excess soil acidity and low soil organic matter. Management options for addressing these factors are evaluated, including replanting. A systematic approach to decision-making about replanting is presented. Practice for replanting is reviewed and it is concluded that evidence to support a general case for replanting is limited, unless based on the introduction of more productive clones and/or better plant spacing.

Evaluation of Soil Acidity in Agricultural Soils of Smallholder Farmers in South Western Ethiopia

The purpose of this study was to investigate the status of soil acidity in agricultural soils in West Wollega, East Wollega and West Showa zones of South Western Ethiopia. A total of 478 soil samples were collected in 2006, 2011 and 2012 G.C from 0-20cm depth. Thirteen representative districts from West Wollega, East Wollega and West Showa zones were selected purposively. Samples were collected from farmers’ crop fields and analyzed at Nekemte Soil Research Center Laboratory for pH and exchangeable cations. Acid saturation percentages were derived by dividing exchangeable aluminum to sum of bases multiplied by 100. Data were analyzed by SAS software. Mean soil pH of different districts in West Wollega, East Wollega and West Showa zones ranged from 4.91-5.29, 4.87-5.30, and 5.25-5.50, respectively. Mean exchangeable acidity in different districts in West Wollega, East Wollega and West Showa zones ranged from 1.89-3.84, 1.61-4.76, and 0.18-0.57cmol(+)/kg, respectively. Mean exchangeable aluminum of different districts in West Wollega, East Wollega and West Showa zones ranged from 1.63-3.53, 1.62-4.71, and 0.05-0.32cmol(+)/kg, respectively. Exchangeable acid saturation in different districts in West Wollega, East Wollega and West Showa zones ranged from 50-76, 16-43, and 1-6%, respectively. Mean soil pH of study zones are rated as very strongly to strongly acidic and degree of acidity varies across districts. Moving from West Wollega zone to West Showa zone the extent of soil acidity and exchangeable acidity decreases. The soils of West Wollega and East Wollega zones have very high exchangeable aluminum and acid saturation percentages. Under such extreme acidity, major crops such as maize and sorghum in West Wollega and East Wollega zone may grow under suboptimal soil conditions. Thus, soil fertility research should geared towards ameliorating acidic soils with liming materials and developing crop varieties tolerant to soil acidity and Al toxicity.