Potassium status of some selected soils under different land‐use systems in the subhumid zone of Nigeria

Abstract

Twenty surface soils (0 to 15 cm), selected to represent a wide range of available potassium (K) status and three different land‐use systems (fodder bank, continuously fertilized cropped land and fallow land) across the subhumid zone of Nigeria, were used for the investigation. Laboratory and greenhouse studies were carried out to assess their K status. Available, non‐exchangeable, and total K were determined. The supplying power of the soils was assessed by exhaustive cropping in the greenhouse using Stylosanthes hamata cv. Verano as the indicator plant. While 75% of fodder banks sampled had available K less than 0.20 cmol/kg, only 50% and 13% of continuously fertilized cropped and fallow lands, respectively, had available K less than 0.20 cmol/kg. Potassium weathering coefficient was highest at the lowest exchangeable K and highest [calcium (Ca) + magnesium (Mg)]/K ratio. Total K ranged from 2.30 to 47.06 cmol/kg, with available K forming 1.47% of the total K. The amount of non‐exchangeable K released and taken up by stylo plant accounted for 23.3 to 83.6% of the total K uptake.     

A participatory evaluation of improved cowpea cultivars in the Guinea and Sudan savanna zones of north east Nigeria

A number of improved varieties have been developed by the International Institute of Tropical Agriculture (IITA), combining diverse plant type with resistance or tolerance to several diseases, insect pests, and parasitic weeds and possessing other good agronomic traits. Trials were established with farmers to evaluate several new IITA-bred cowpea varieties on-farm in a process of participatory varietal selection. Central to this has been a ‘mother-daughter’ approach with researcher-managed ‘mother’ trials and farmer-managed ‘daughter’ trials in order to combine researchers' and farmers' criteria in evaluation of new varieties. In both set of trials, new varieties IT89KD-391, IT97K-499-35, and IT89KD-288 were favoured by farmers because of their high grain and fodder yields. Farmers have also shown interest in the continuous use of a local variety Kanannado Brown. It is suitable for relay intercropping; having a creeping habit, and the ability to smother weeds. The brown seeds fetch higher market prices. The implications are that improved cowpea varieties should be suitable for relay-intercropping and controlling weeds, be brown in colour, have large grain size, be pest resistant as well as give high yields of grain and fodder. At the same time, it is important that the farmer's criteria should be considered in breeding and varietal selection programmes.     

Soil chemical and biological characteristics influence mineralization processes in different stands of a tropical wetland

In the Caribbean, Pterocarpus officinalis swamp forest, a coastal freshwater wetland, has been locally transformed by human activities into Colocasia esculenta monoculture (under the swamp forest) or pasture (where deforestation has occurred). The aim of this study was to evaluate the impact of three land uses of this tropical wetland (swamp forest, C. esculenta monoculture and pasture) on soil abiotic and biological features. We hypothesized that increasing the level of ecosystem alteration by agricultural intensification would negatively impact soil chemical characteristics, soil fauna diversity and carbon mineralization. As expected, land use significantly affected soil characteristics and changes followed the increasing intensity of land use. The ‘undisturbed system’, that is swamp forest, was characterized by a large soil organic matter content, a high level of soil moisture, a small phosphorus content and a slightly lower pH. These characteristics were correlated with a small faunal abundance and diversity and slow carbon (C) mineralization. The ‘low disturbance system’, that is C. esculenta monoculture, was the closest to swamp forest characteristics and changes between the both systems principally concerned a very slight decrease in organic matter content and very small increase in C mineralization and Coleoptera diversity. By contrast, all parameters (soil chemical characteristics, C mineralization and faunal abundance and diversity) were impacted in the most intensive land‐use, pasture. Our study confirmed that agricultural practices have an influence on soil fauna and C mineralization processes in wetlands. Moreover, our study suggested that a C. esculenta traditional agroecosystem under swamp forest cover could be considered as an ‘eco‐friendly’ agricultural practice.     

Fodder production and soil health with conjunctive use of saline and good quality water in ustipsamments of a semi‐arid region

Food and fodder shortage in arid and semi‐arid regions force farmers to use marginal quality water for meeting the water requirement of crops which result in low quality, reduced production and an adverse impact on soil properties. A field study on loamy‐sand (Hyperthermic Typic Ustipsamments) saline soil was conducted during 1999–2001 at Central Institute for Research on Buffaloes, Hisar. This involved assessment of effects of conjunctive use of saline water, EC = 4·6–7·4 dSm⁻¹, SAR = 14–22 ((mmol⁻¹)^½ with good quality water on five fodder crop rotations: oat‐sorghum (Avena sativa‐–Sorghum bicolor), rye grass–sorghum (Loleum rigidum—Sorghum bicolor), Egyptian clover—sorghum (Trifoleum alexandrinum—Sorghum bicolor), Persian clover—sorghum (Trifoleum resupinatum—Sorghum bicolor) and Indian clover–sorghum (Melilotus indica—Sorghum bicolor) and certain soil properties associated with it. Leguminous winter fodder crops were more sensitive to poor quality water use. Reductions in fodder yield with use of saline water alone throughout season were 85, 68, 54, 42, 36 and 26 per cent in Indian clover, Egyptian clover, Persian clover, oat, rye grass and sorghum respectively as compared to good quality water. Leguminous fodder crops produced protein rich (12–14 per cent) and low fibre (18–20 per cent) fodder as compared to poor quality grassy fodder under good quality water irrigation but their quality deteriorated when saline water was used. These leguminous crops accumulated proportionately higher Na⁺ (1·58 per cent) resulting in adverse impact on their growth as compared to grassy fodder crops. Higher soil salinity (12·2 dSm⁻¹), SAR = 20 (mmol⁻¹)^½ was recorded with saline water irrigation; and slight adverse impact was noticed on infiltration rate and contents of water dispersible clay. Alternate cyclic use of canal and saline water could be an option for fodder production under such conditions. Copyright © 2006 John Wiley & Sons, Ltd.     

A social learning video method: Identifying and sharing successful transformation knowledge for sustainable soil management in Switzerland

To enhance sustainable land use, a From Farmer to Farmer project was conducted in Switzerland (2001–2010). A multi‐stakeholder discussion group co‐produced nine videos with experienced farmers and wine producers showing sustainable soil management practices. We analysed the video audio‐visual content and drew on reflections of the co‐production process, referring to concepts of system, target and transformation knowledge, as well as on social learning. The analysis showed a broad range of means (or actions) for sustainable soil management in arable land management, fodder production and wine growing that are aligned to transformation knowledge. The research showed that farmers refer to three phases of social learning, light‐bulb moments, coping with challenges and gaining successful expertise. These are not just linear processes of individuals. Four types of social learning were found in the video analysis: (a) learning from observing actions of others, (b) sharing experiences with storytelling, (c) informal social interactions and (d) being a role model with a large social network. Videos enable transformation knowledge to be shared with peers using storytelling; this powerful narrative communication style provides credibility and respects the ‘thought style’ of the target audience group. We conclude that for successful implementation of sustainable actions, it is important to address a specific target group and share their transformation knowledge built upon system and target knowledge. The social learning video method is a viable way to enable social learning between science, administration and practice and has potential for fostering change in sustainable soil management.     

Mixed tree‐vegetative barrier designs: experiences from project works in northern Vietnam

There has been an increased interest in the use of vegetative barriers in acid‐infertile upland management systems in Southeast Asia. This paper analyses the experimental designs and policies in early‐1990s of using vetiver grass barriers (Vetiveria zizanioides L.) in microwatersheds with short‐rotation tree plantations in Vinh Phu Province, Vietnam. Four different mixed tree‐vetiver models on degraded Ferric‐Plinthic Acrisols are discussed. It is concluded that the institutional approach of demonstrating vetiver barriers as a model had a poor cost‐wise performance, and that the model itself did not address the underlying issues of land degradation due to uncontrolled harvest of organic matter from the forest floors. The institutional approach was tainted with price distortions and ‘disbursement‐oriented’ actions. Alternative and more flexible on‐farm approaches, using V. zizanioides or the indigenous leguminous shrub Tephrosia candida (Roxb.) DC as vegetative barriers, were found to be more cost‐effective and likely to have a higher rate of adoption among farmers. The institutional changes in land allocation policies (securing long‐term usufruct users and transfer rights of agricultural and forest land) that took place in Vietnam in the early 1990s, in combination with a reorientation of programme policies to support needs of individuals and farmers' households, are hypothesized to have contributed more to the ‘regreening’ of the hills, than any single approaches of technical barrier designs by the Swedish‐Vietnamese Forestry Co‐operation Programme (FCP) in northern Vietnam. Copyright © 2002 John Wiley & Sons, Ltd.     

Protea Nutritional Problems and Soil Nutrient Status in Norton-Darwendale and Juliasdale Farming Areas,Zimbabwe

A study was conducted from November 2000 to February 2001 to establish causes of poor protea plant growth in the Juliasdale and Norton-Darwendale commercial farming areas of Zimbabwe. Soil and leaf samples from farmer-perceived “deficient” and “normal” areas were analyzed. Soils perceived by farmers to be deficient had lower levels of phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) compared with the normal soils. In Juliasdale, all cultivars from perceived-deficient samples had lower levels of zinc (Zn) in leaves compared with normal leaves. Leucospermum cultivar ‘Tango’ and Protea cultivar ‘Moonshine’ also had low levels of P and Zn in the deficient plants compared with the normal plants. In Norton-Darwendale, the Protea cultivar ‘Moonshine’ had lower levels of nitrogen (N), P, K, and boron (B) in perceived-deficient samples compared with normal samples. Soil-analysis data were generally comparable to leaf-analysis data, indicating the potential use of leaf analysis to determine nutritional requirements of proteas.     

The Effects of Expansive Shrubs on Plant Species Richness and Soils in Semi‐arid Communal Lands,South Africa

Expansion by expansive species can have severe ecological, social and economic impacts through the reduction of ecosystem goods and services and species richness. However, expansion by expansive species may also offer benefits to ecosystems and humans, through the supply of ecosystem goods and services (such as firewood, fodder and fruits), as well as potentially offering refugia in heavily used landscapes. Here, we examine the effects of four expansive dwarf shrub species (Aspalathus subtingens , Dicerothamnus rhinocerotis , Pteronia incana and Oedera genistifolia ) on plant species richness (at the point scale), vegetation cover, soil properties and whether the expansive species offer refugia to other species. Plant species richness, cover and soil properties were recorded in 1‐m² quadrats located within a mosaic of expanded and non‐expanded patches for the four expansive shrub species. Plant species richness was significantly higher in the non‐expanded areas compared to the expanded ones for all four expansive species. Some of the expansive shrubs provided refugia to certain plant species and limited the frequency of other species. With regard to species composition, there was little separation of expanded and non‐expanded samples within sites, indicating that the site factors were stronger determinants of plant species richness and composition than expansion. Therefore, it is more likely that the reduction in species richness in expanded sites is caused by multiple drivers, including vegetation attributes cover, litter cover and soil nutrients (organic C, Zn and P) and soil compaction. Copyright © 2017 John Wiley & Sons, Ltd.     

Clone selection of woody ornamentals in Finland

Fifty clones of the genera Forsythia, Hydrangea, Lonicera, Philadelphus and Viburnum were cultivated in comparative field trials at five sites in Finland in 1989–93. The aim was to find the hardiest and the most valuable clones to be recommended for landscape gardening. The evaluation covered about 30 traits which were recorded annually. Most attention was paid to winter‐hardiness, resistance to diseases and pests, and ornamental value. The data were analysed using both statistical and non‐statistical methods. A combination of these proved to be a successful method for selecting the clones with the highest value for production. Nine clones were selected as recommendable clones. The Hydrangea paniculata cultivars ‘Grandiflora’, ‘Praecox’ and ‘Mustila’ were found to be valuable and recommendable. Several Lonicera clones succeeded well and were renamed. Three clones were selected as being suitable for different purposes: L. tatarica ’Sanna’ suits well for hedges, L. x bella ’Dropmore’ is white‐flowered, and L. x bella ’Sakura’ has a special growth habit. A true‐to‐type Philadelphus pubescens clone was renamed ‘Tuomas’ and an abundantly blossoming and hardy P. lewisii hybrid was renamed ‘Tähtisilmä’. Finnish Viburnum opulus clones representing a hardy type with plenty of blossoms were renamed ‘Pohjan Neito’.     

A software tool for estimating the capacity of agricultural land in England and Wales for recycling organic materials (ALOWANCE)

Agricultural Land and Organic ‘Waste’: A National Capacity Estimator (ALOWANCE) is a GIS‐based tool that estimates the available agricultural landbank in England and Wales for recycling organic materials based on a number of physical and practical constraints, and legislative restrictions. It can be used to identify areas where there is a potential shortage or surplus of available agricultural land and to determine the length of time for which the agricultural landbank would continue to be available to receive organic materials. Two versions of ALOWANCE have been developed. ALOWANCE‐PLUS is a PC‐based tool that provides the full functionality of ALOWANCE to a small number of ‘expert’ users. It incorporates scenario testing capabilities, allowing the agricultural landbank capacity to be calculated interactively. ALOWANCE‐ONLINE is a web‐based version that provides information to ‘general’ users, including pre‐selected map ‘layers’ (generated from ALOWANCE‐PLUS) and a simple query tool. Results from ALOWANCE‐PLUS showed that after exclusions and after accounting for current sources of organic materials (livestock manures, biosolids, compost, paper crumble and digestate), the estimated agricultural landbank in England and Wales for the addition of ‘new’ sources of organic materials was c. 5.1 million ha. Spatial representations showed that in some parts of the country (e.g. north‐west England), the agricultural landbank was already under ‘pressure’ and transport of any future emerging sources of organic materials away from these areas may be required.     

The soil-protective role of specially-shaped plant roots

Some trees and shrubs which grow on steep slopes, abrupt banks alongside watercourses, or the sides of sunken roads, shape their secondary roots of the first order, and sometimes even the main root, in such a way as to develop in them a knee-like curvature, turning back into the more compact soil. This feature, here referred to as ‘edaphoecotropism’, is considered to be the results of a number of interacting physical of this phenomenon may be cited the response by roots to undesirable extreme topographic conditions of the site—some kind of ‘escape’ by the root into a more favourable environment—and a one-sided provocation of the root's growing portion, which produces variations in the distribution of auxin and thus the peculiar curvature of the root. This ‘edaphoecotropic’ orientation of the main root-branches in trees and shrubs is of importance in the safe anchoring of plants in the soil and, hence, increasing the stability of the earth or other slope or ‘cliff’.     

What drives farmers to increase soil organic matter? Insights from the Netherlands

Soil organic matter (SOM) is an important resource base for arable farming. For policies on SOM to be effective, insight is needed on why and under which conditions farmers are willing to increase SOM content. This study used the theory of planned behaviour to analyse what prevents or encourages Dutch farmers to increase the SOM content of their fields. In an online survey, 435 arable farmers were asked questions to understand their attitude (perceived benefits), subjective norm (social pressure) and perceived behavioural control (anticipated impediments and obstacles) related to management of SOM. Farmers’ answers were related to their intention to increase SOM content, use of organic materials and perceived increase in SOM content. Our results showed that Dutch farmers are well aware of the possible benefits of SOM content for crop productivity. Farmers’ attitude, subjective norm and perceived decrease in SOM content were significantly related to their intention to increase SOM content. In our farm survey, this intention was very strong: 90% of the farmers stated a high or very high intention to increase the SOM content of their fields. A higher intention to increase SOM content was correlated with the use of organic materials as expressed as total and effective C (P  = 0.003 and P  = 0.002, respectively), but this did not lead to a perceived increase in SOM content. From a farmer's point of view, this indicates that increasing SOM content is to a large degree beyond their direct influence. The Dutch Manure and Fertiliser Act, costs of organic inputs and the need to cultivate profitable crops (such as potatoes or sugar beet) were indicated as important impeding factors for increasing SOM content.     

Characterization of zinc in contaminated soils: complementary insights from isotopic exchange,batch extractions and XAFS spectroscopy

Isotopic exchange (IE) of trace metals is an established method for characterizing metal reactivity in soils, but it is still unclear which metal species are isotopically exchangeable. In this study, we used IE to quantify ‘labile’ zinc (Zn) in 51 contaminated soils that were previously studied by Zn K‐edge X‐ray absorption fine structure (XAFS) spectroscopy and sequential extraction (SE). All soils had been contaminated by runoff water from 17‐ to 74‐year‐old galvanized power‐line towers. They covered a wide range in pH (4.0–7.7), organic carbon (0.9–10.2%), clay (3.8–45.1%) and Zn concentrations (251–30 090 mg kg^?1). Isotopic exchange was also performed on selected Zn minerals used as references for linear combination fitting of XAFS spectra. The isotopically exchangeable fraction (%E) of Zn generally decreased with increasing pH, but small %E values were also observed for acidic soils with a large fraction of Zn in hydroxy‐interlayered minerals (Zn‐HIM). The fraction of Zn identified by XAFS spectroscopy as (tetrahedrally and octahedrally coordinated) ‘sorbed Zn’ agreed reasonably well with the isotopically exchangeable fraction but was in many cases larger than the %E, indicating that some ‘sorbed Zn’ may be isotopically non‐exchangeable, such as Zn sorbed in micropores of Fe oxyhydroxides. Zinc identified by XAFS spectroscopy as Zn precipitates (Zn phyllosilicates, Zn‐layered double hydroxide (Zn‐LDH) or hydrozincite) or as Zn‐HIM was largely isotopically non‐exchangeable (‘non‐labile’). Comparison between IE and extraction results suggested that the isotopically exchangeable Zn was mainly extracted in the first two fractions of the SE. However, non‐labile Zn was also extracted in these first two fractions for some soils, including a hydrozincite‐containing soil. Despite the presence of Zn‐LDH and/or Zn phyllosilicates in almost all soils, the Zn concentrations in solution and labile Zn increased with increasing soil total Zn at a given pH, which contradicts the concept of precipitation control by a single phase. Solution Zn was well predicted from the labile Zn following a sorption model.     

MRI studies of flow and dislocation of model NAPL in saturated and unsaturated sediments

In this article, we explore the possibilities of studying transport phenomena that involve non‐aqueous phase liquids (NAPL) by means of magnetic resonance imaging (MRI) with a paramagnetic contrast agent. We studied n‐octanol as a model NAPL, especially in alcohol flooding in a water‐saturated sediment, and flood‐drainage‐cycles in a temporally unsaturated sediment column. While the ‘natural’ relaxation time contrast between water and n‐octanol often allows a distinction of the two liquids in a quartz‐sand sediment, the use of Mn²⁺‐ions dissolved in the water phase as a ‘biphasic’ contrast agent allows much better discrimination between the different liquid phases and also considerably faster imaging. Using a 3D FLASH sequence, a NAPL‐saturated region can be visualized against a background of water‐saturated sediment in 11 s with a resolution of 1.9 × 1.9 × 3.2 mm³.     

Ozone tolerances of soybean cultivars and near‐isogenic lines in a fumigation chamber

Ozone (O₃) toxicity is a potential yield‐limiting factor for soybean (Glycine max L. Merr.) in the United States and worldwide. The most economical solution to the problem is to use O₃‐tolerant cultivars. Thirty‐four cultivars and 87 near‐isogenic lines (NILS) of soybean were screened for O₃ tolerance in a fumigation chamber (250 ppb for three hrs). Most tolerant cultivars tested were ‘Cloud’, ‘T‐276’, ‘T263’, and ‘Kindu’. Moderately tolerant cultivars included ‘Davis’, ‘T‐210’, and ‘Elton’. Most sensitive cultivars were ‘Corsoy 79’, ‘Noir’, and ‘Midwest’. The original ‘Clark’ cultivar was not tested, but ‘Clark 63’ tended to be more tolerant than ‘Harosoy’. The aluminum (Al)‐tolerant ‘Perry’ cultivar also tended toward greater O₃ tolerance than the Al‐sensitive ‘Chief’, as observed earlier. Our rankings of ‘Hark’ as moderately sensitive and ‘Davis’ as moderately tolerant are also in agreement with earlier reports. Among NILS, the order of O₃ tolerance was generally Williams>Clark>Harosoy, but differences were also observed within these parental groups. For example, L68–560 was more tolerant than some other NILS of ‘Harosoy’. ‘L76–1988’ appeared more tolerant to O₃ than other NILS of ‘Williams’, but all ‘Williams’ NILS were more tolerant than most NILS of ‘Harosoy’ and ‘Clark’. Ozone‐tolerant and ‐sensitive soybean cultivars or NILS identified in our study may be useful tools in studies on mechanisms of 03 tolerance and differential 03 tolerances in plants and in the development of ameliorative measures.     

How to characterize ‘good’ and ‘greening’ in the EU Common Agricultural Policy (CAP): the case of clay soils in the Netherlands

The change in the Common Agricultural Policy (CAP) of the European Union from product to producer support, including requirements for ‘good agricultural and environmental conditions’ and ‘greening’, is excellent. However, these requirements are now defined in rather general terms. Questions can be raised about suitable indicators, and there is a recognized need for effective management recommendations to support farmers in achieving the required ‘good’ conditions. These recommendations are bound to be quite different for different soils in different countries. A study of Dutch clay soils was based on a storyline describing current problems and management options for improvement, which were quantified using a soil–water–crop simulation model. Indicators were defined for agricultural conditions and suggestions made for the use of the model in a predictive mode to help farmers improve their soil management. Environmental conditions were judged by current environmental guidelines for water and air. When modelling, implicit assumptions that soils are homogeneous were shown to be unrealistic for these clay soils, requiring development of innovative methods and procedures, presenting a challenge for soil research.     

Investigating Iranian Farmers' Satisfaction With Agricultural Extension Programs Using the American Customer Satisfaction Index

The aim of this article is to investigate and measure farmers' satisfaction regarding extension services to better understand why farmers do or do not participate in such programs in Iran. Our study sample consisted of 240 farmers selected through simple quota random sampling (160 male and 80 female) from a list of names from the extension organization. Data were gathered through a face-to-face survey of farmers. Structural equation modeling analysis revealed that perceived quality and perceived value significantly predicted farmers' overall satisfaction. Furthermore, farmer satisfaction can predict farmers' loyalty to extension program activities. From a practical point of view, the present study provides a justification for using perceived quality and perceived value in policy and decision making that seeks to encourage farmers to use agricultural extension programs (AEPs).     

Soil acidity under multiple land-uses: assessment of perceived causes and indicators,and nutrient dynamics in small-holders’ mixed-farming system of northwest Ethiopia

Knowledge on farmers’ perspectives is of paramount importance in order to design appropriate agricultural research and development interventions attuned to local farming systems. A participatory rural appraisal was conducted in order to understand perceived causes and indicators of soil acidity under multiple land-uses in three Districts of northwest Ethiopia. Soil samples were also collected from five dominant land-uses. The samples were analysed for soil pH, exchangeable acidity and other physico-chemical properties. The result indicated that the pH_(H2O) of most of the soils in the study sites were in a strongly acidic range (4.6–5.5). Gashena Akayita of the Banja District was the most acidic of all. Among the land-uses, eucalyptus fields were the most acidic followed by crop outfields and grazing lands in that order. At all the study sites, exchangeable Al was detected in soils having a pH of less than 5.0. Overall, the nutrient dynamics showed variation across land-uses and study sites. Farmers’ perceived causes of soil acidity included: soil erosion; contending use of fertility replenishing local resources; abandoning traditional fertility management practices and minimal use of external inputs. The farmers attributed the exclusive use of acid-forming inorganic fertilizers to exhaustion of the soil. Various land and soil characteristics, plant growth attributes, changes in genetic diversity were mentioned as indicators of soil acidity. Particularly, the farmers used prevalence of acidophilic weed species on crop fields and grazing lands as marker of strongly acidic soil. Farmers’ perceived causes and indicators were in agreement with scientific facts and can be utilized as input in designing sustainable acid soil management strategies. Decline in genetic diversity of the once widespread crop species and land races, and expansion of newly introduced soil acidity tolerant species, suggests the need to undertake rescue collections in these areas.     

Influence of nitrogen and potassium on micronutrient content of fifteen cultivars of bermudagrass

Abstract

There is limited information concerning the micronutrient composition of different turfgrass species and cultivars. Bermudagrass [Cynodon dactylon (L.) Pers.] is an important turfgrass utilized throughout the Southeastern and Southwestern states and the transition zone of the United States. A study was conducted to determine the effects of different rates of nitrogen (N) and potassium (K) on the micronutrient content of fifteen bermudagrass cultivars. The cultivars utilized were: ‘Ormond’, ‘Texturf 10’, ‘Tiflawn’, ‘Tufcote’, and ‘U‐3’ [Cynodon dactylon (L.) Pers.]; ‘Everglades’, ‘Midiron’, ‘Midway’, ‘Pee Dee’, ‘Santa Ana’, ‘Tifdwarf, ‘Tifgreen’, ‘Tifway’, and ‘Tifway II’ [Cynodon dactylon (L.) Pers. x Cynodon transvaalensis Burtt‐Davey]; and ‘Sunturf [Cynodon magennisii Hurcombe]. The study was a 2x2 factorial with the factors being two levels each of N and K imposed on the fifteen cultivars. It was a completely randomized design with three replications. The N and K rates were 227 g N and 227 g K 93 m^‐2 month^‐1 (low rates) and 454 g N and 454 g K 93 m^‐2 month^‐1 (high rates) that resulted in four N:K treatment combinations as follows: 1) high N:high K; 2) high N:low K; 3) low N:high K; and 4) low N:low K. Plant tissue samples were collected in late August and analyzed for boron (B), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn). There were differences for the Cu, Fe, Mn, and Zn concentrations for several cultivare under certain treatment combinations. Zinc concentrations exceeded the sufficiency range in all but one instance, while there were several cases in which Fe and Mn concentrations were above the sufficiency range. The levels of B and Cu were within the sufficiency range and there were no differences for B.     

Aluminum toxicity in tomato. Part 2. leaf gas exchange,chlorophyll content,and invertase activity

The effect of aluminum (Al) toxicity on leaf gas exchange, leaf chlorophyll content, and sucrose metabolizing enzyme activity of two tomato cultivars (Lycopersicon esculentum Mill. ‘Mountain Pride’ and ‘Floramerica') was studied to determine the mechanism of growth reduction observed in a related study (Simon et al., 1994, Part 1). Plants were grown in diluted nutrient solution (pH 4.0) with 0, 10, 25, or 50 μM. Al for 16 days. Leaf gas exchange was reduced 2–3 fold in both cultivars as Al concentration increased. Gas exchange of ‘Mountain Pride’ was more sensitive to Al toxicity than ‘Floramerica’, agreeing with growth responses observed. Reductions in carbon dioxide (CO₂) assimilation rate appeared to be due to nonstomatal factors in ‘Floramerica’, but stomatal and non‐stomatal limitations in ‘Mountain Pride’. Chlorophyll content of leaves was not affected by Al. Acid invertase (AI) and neutral invertase (NI) activity of roots responded consistently to Al concentration in both cultivars. Root AI and NI activity decreased to a greater extent for ‘Mountain Pride’ than for ‘Floramerica’.