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.     

Establishing native plants on newly‐constructed and older‐reclaimed sites along West Virginia highways

Many state highway departments in the USA must use native plants for revegetating roadsides. We conducted two field studies in West Virginia to assess native plant establishment under two different conditions. On newly‐constructed sites, native species were seeded alone or combined with non‐native species. On older roadsides, native species were seeded in disturbed existing vegetation. In the first study, we used four seed mixtures comprised of seeds of native and non‐native species, and two N‐P‐K fertilizer treatments at three newly‐constructed sites. Native, warm‐season grasses were slow to establish and only contributed 25 per cent cover in some plots after three years. Indiangrass (Sorghastrum nutans [L.] Nash), big bluestem (Andropogon gerardii Vitman), Brown‐Eyed Susan (Rudbeckia triloba L.), and wild senna (Cassia hebecarpa Fernald) were the only seeded native species found. Fertilizer at 150 kg ha⁻¹ of 10‐20‐10 showed little influence on increasing plant cover. In the second study, we disturbed three different‐aged established stands of vegetation composed of tall fescue (Festuca arundinacea Screb.) and crownvetch (Coronilla varia L.) by mowing, herbicide, or tillage, and native plants were seeded with and without fertilizer. Native cover was <10 per cent in all plots during the first year, but greatly increased by the second year to as much as 45 per cent in tilled plots, indicating that disturbance was necessary for natives to become important contributors within 2 years. Only switchgrass (Panicum virgatum L.), little bluestem (Andropogon scoparius Vitman), partridge pea (Chamaecrista fasciculate Michx.), and Brown‐Eyed Susan were observed in plots. Fertilizer at 300 kg ha⁻¹ of 10‐20‐10 did not increase native plant cover on these sites. Based on our results, introducing or increasing the cover of native species along roadsides requires (1) reducing competition from non‐native species, and (2) longer time periods for these slower‐establishing species to be observed. Copyright © 2008 John Wiley & Sons, Ltd.     

Selection of Adequate Species for Degraded Areas by Oil‐Exploitation Industry as a Key Factor for Recovery Forest in the Ecuadorian Amazon

One of the requirements for the forest restoration of soils disturbed by the oil‐exploitation industry is that saplings be able to endure soil‐adverse conditions. In this study, saplings of 20 species susceptible to be used in reforestation programs were evaluated for their ability to grow on substrates derived from soils disturbed by petroleum extractions in the Ecuadorian Amazon. Seeds of each species were planted in germination trays. Once seedlings reached 5 cm in height they were transplanted to plastic bags with three treatment substrates: two derived from petroleum‐exploitation activity (soils from mud and drill cutting cells and from areas surrounding oil wells) and a control soil. Plant survival rate, stem height, and diameter were measured on a weekly basis until 14 weeks after transplantation, when we harvested the plants and also measured plant biomass and calculated the Dickson quality index for each species. Oil‐exploitation by‐product substrates impaired the performance of many saplings, with the substrate from mud and drill cutting cells being the one that most affected plant performance. Only saplings of five native species in the Amazon basin—Apeiba membranaceae, Cedrelinga cateniformis, Inga densiflora, Myroxylon balsamum, and Pouroma cecropiifolia—exhibited high or similar Dickson quality index values in all soil treatments and performed better than the rest. The use of these five species in remediation of soils disturbed by petroleum extraction in the Amazon basin could prove important because of their high potential to adapt to these disturbed sites. Copyright © 2016 John Wiley & Sons, Ltd.     

The relative efficiency of four representative cropland conversions in reducing water erosion: evidence from long‐term plots in the Loess hilly area,China

Large areas of traditional slope cropland were recently converted to other land‐use types in the semiarid Loess Plateau of China. In this study, we selected four representative conversion options of slope croplands, i.e., pastureland rotated with cropland (cultivated with Medicago sativa L. and rotated with Triticum aestivum L.), shrubland and woodland (afforested with Hippophae rhamnoides L. and Pinus tabulaeformis), and grassland (native herbage Stipa breviflora) to study the effect of land‐use conversion by comparing with traditional cropland. Compared with slope cropland, the relative effects of different conversion options on surface runoff and soil erosion were assessed over a 14‐year measurement period. Observations showed that distinct features and consequences of vegetation succession were found among the conversion options. Plots of shrubland had the highest vegetation coverage with dense undergrowth; natural herbaceous and subshrub species gradually spread into plots of grassland resulting in higher vegetation cover. Neither bushes nor herbs colonized the plots of Pinus tabulaeformis, which resulted in a higher percentage of bare soil. Significant differences in runoff generation, sediment yield and conservation efficiencies among the selected conversion options were detected through an analyses of variance (ANOVA). Compared with cropland, total runoff and sediment decreased by 65 per cent and 95 per cent in shrubland, 41 per cent and 92·5 per cent in grassland, 18 per cent and 77 per cent in woodland, and 12 per cent and 58 per cent in pastureland, respectively. The ranking of soil and water conservation efficiencies was shrubland > grassland > woodland > pastureland > cropland. Based on the effectiveness of soil and water conservation, shrubland and grassland are highly recommended as promising options for cropland conversion projects. However, pastureland and woodland are not suggested as potential options for slope‐cropland conversion because of low soil and water conservation in the long term. Copyright © 2006 John Wiley & Sons, Ltd.     

Avoidance of degradation of alpine pasture through grazing management: Investigations of change in vegetation nutrition characteristics as a consequence of sheep grazing at different periods of the growing season

The maintenance of animal husbandry in mountain areas can prevent the general degradation of the landscape due to the disuse of pastures and meadows. This study investigated the changes over the productive season of the nutritional characteristics of an Alpine pasture with the objective of maintaining grazing sheep fed only on the available herbage. Four homogeneous areas of an Alpine pasture located in northeast Italy were cut at the end of June, July, August, and September, simulating different grazing periods by the animals. the herbage was sampled to estimate the botanical and chemical composition and fed to four Lamon breed wethers (76-5 kg average bodyweight) measuring voluntary intake, digestibility and energy value. the botanical composition of the pasture changed as the vegetative season advanced, with a progressive increase in grass species. the protein content decreased from 16-3 per cent dry matter in the first grazing period, to 9-6, 9-9 and 7-9 per cent, respectively, in the following, while the neutral detergent fibre increased from 62-1 per cent in the first period to 78-4, 77-7 and 79-4 per cent in July, August, and September, respectively. The nutritional evaluation of the forage material was carried out using four Lamon wethers housed in single metabolic cages. the voluntary intake of herbage was 1151 g d⁻¹ at the end of June, decreasing significantly to values below the recommended requirement for maintenance in the subsequent periods of the study. No selectivity was observed for specific botanical species. the in vivo digestibility of the herbage was lowered by the delay in the use of the pasture and the resulting energy intake met the recommended maintenance requirements for grazing only in the earlier period of pasture consumption. the late use of the pasture and the corresponding underfeeding of the animals would necessitate a feed supplementation to limit excessive loss of bodyweight. the conclusion is that the objective of maintaining grazing animals in mountain areas without any supplementation can be carried out exclusively by adopting an efficient grazing management able to provide good quality pasture throughout the vegetative season.     

Leaf litter decomposition and nitrogen concentration in decomposing leaves of a quercus seme‐carpifolia smith forest stand of Kumaun Himalaya

Abstract

Decomposition patterns of Quercus semecarpifolia (Kharsu oak; tree species), Viburnum cotinifolium, and Berberis asiatica (shrub species), Senecio rufinervis, Polygonum amplexicaule, and Selinum candollii (herb species) were studied. Sixty‐five per cent weight loss occurred in Kharsu oak in 360 days, whereas total disappearance of leaf litter was achieved in 360 days in both the shrub species and in 210 days in case of herb species. A highly negative correlation (r² = 0.861 to 0.949) was established between nitrogen (N) concentration and per cent weight remaining during decomposition. The absolute amount of N at various periods was calculated and N was never found more than 100% of initial mass.     

Soil degradation in Kabd area,southwestern Kuwait City

Adverse environmental impacts of human activities are the main causes of soil degradation in the desert of Kuwait in general, and in Kabd area in particular. In this study, assessment of soil degradation in open and protected sites has been carried out using field measurements and laboratory investigations. The overall status of vegetation is nearly twice as low in vegetation cover in the open sites than in the protected ones due to overgrazing and off‐road transport. Compaction of soil due to pressure exerted on the soil by vehicles led to a significant reduction in its porosity, permeability and infiltration capacity. The average infiltration rate of the compacted soils is 51 per cent lower than that of the non‐compacted soils. The bulk density of the non‐compacted soils is 3.4 per cent lower than that of compacted soil. The average topsoil resistance of compacted soils has increased by 83 per cent in comparison with non‐compacted soil. Using the least squares method a relation between infiltration rate (IR) and penetration resistance (PR) of the topsoil for the study areas is found (i.e. IR = −0.148 PR + 1.85 with R² = 25 per cent). Soil strength within the soil profile shows maximum penetration resistance readings at 11.5 cm depth in average in compacted soils, while it shows maximum readings at 34.6 cm depth in average in non‐compacted soils. The adverse changes in the chemical properties due to soil compaction is also investigated. A restoration plan is needed in order to reduce land degradation. Copyright © 2002 John Wiley & Sons, Ltd.     

Three hydro‐seeding revegetation techniques for soil erosion control on anthropic steep slopes

Erosion control at low–medium radioactive waste disposal sites is an important concern. A study was carried out in El Cabril (Córdoba, Spain) on two 40 per cent anthropic steep slopes in order to test the effectiveness of hydro‐seeding techniques for controlling soil erosion. Two groups of 10 m × 3 m plots were established. The treatments tested were: hydro‐seeding with the application of vegetal mulch (VM); hydro‐seeding with added humic acids (HA); hydro‐seeding with vegetal mulch and humic acids added (VM + HA); and a control without hydro‐seeding or soil amendment (C). Fifteen run‐off producing rainfall events were recorded during the study period, with intensities ranging between 2 mm h⁻¹ and 33·6 mm h⁻¹. All treatments significantly reduced runoff and soil loss (p < 0·05). The VM+HA treatment was the most effective, reducing 98·5 per cent of total soil loss. The HA treatment (97·1 per cent reduction) was also more effective than the VM treatment (94·8 per cent reduction). A great reduction in runoff and sediment yield was observed in the treated plots during the first stages after hydro‐seeding. This result may be attributed to the combined effect of: (a) the protection against raindrop impact due to the application of straw and mulch to the soil surface, and (b) a general improvement in the soil's structure brought by the organic amendments. Seven months after hydro‐seeding, an increase in the density of the plant cover could be added to the beneficial effects mentioned above. Copyright © 2000 John Wiley & Sons, Ltd.     

Reclamation and salt leaching efficiency for tile drained saline‐sodic soil using marginal quality water for irrigating rice and wheat crops

Due to increased population and urbanization, freshwater demand for domestic purposes has increased resulting in a smaller proportion for irrigation of crops. We carried out a 3‐year field experiment in the Indus Plains of Pakistan on salt‐affected soil (EC_e 15·67–23·96 dS m⁻¹, pH_s 8·35–8·93, SAR 70–120, infiltration rate 0·72–0·78 cm h⁻¹, ρ _b 1·70–1·80 Mg m⁻³) having tile drainage in place. The 3‐year cropping sequence consisted of rice (Oryza sativa L.) and wheat (Triticum aestivum L.) crops in rotation. These crops were irrigated with groundwater having electrical conductivity (EC) 2·7 dS m⁻¹, sodium adsorption ratio (SAR) 8·0 (mmol L⁻¹)^1/2 and residual sodium carbonate (RSC) 1·3 mmol_c L⁻¹. Treatments were: (1) irrigation with brackish water without amendment (control); (2) Sesbania (Sesbania aculeata) green manure each year before rice (SM); (3) applied gypsum at 100 per cent soil gypsum requirement (SGR) and (4) applied gypsum as in treatment 3 plus sesbania green manure each year (GSM). A decrease in soil salinity and sodicity and favourable infiltration rate and bulk density over pre‐experiment levels are recorded. GSM resulted in the largest decrease in soil salinity and sodicity. There was a positive relationship between crop yield and economic benefits and improvement in soil physical and chemical properties. On the basis of six crops, the greatest net benefit was obtained from GSM. Based on this long‐term study, combined use of gypsum at 100 per cent soil gypsum requirement along with sesbania each year is recommended for soil amelioration and crop production. Copyright © 2010 John Wiley & Sons, Ltd.     

Enhancing the productivity of high‐magnesium soil and water resources in Central Asia through the application of phosphogypsum

Recent evidences from some irrigated areas worldwide, such as Central Asia, suggest that water used for irrigation contains magnesium (Mg²⁺) at levels higher than calcium (Ca²⁺). Excess levels of Mg²⁺ in irrigation water and/or in soil, in combination with sodium (Na⁺) or alone, result in soil degradation because of Mg²⁺ effects on the soil's physical properties. More than 30 per cent of irrigated lands in Southern Kazakhstan having excess levels of Mg²⁺ are characterized by low infiltration rates and hydraulic conductivities. The consequence has been a gradual decline in the yield of cotton (Gossypium hirsutum L.), which is commonly grown in the region. These soils require adequate quantities of Ca²⁺ to mitigate the effects of excess Mg²⁺. As a source of Ca²⁺, phosphogypsum—a byproduct of the phosphorous fertilizer industry—is available in some parts of Central Asia. In participation with the local farming community, we carried out a 4‐year field experiment in Southern Kazakhstan to evaluate the effects of soil application of phosphogypsum—0, 4·5, and 8·0 metric ton per hectare (t ha⁻¹)—on chemical changes in a soil containing excess levels of Mg²⁺, and on cotton yield and economics. The canal water had Mg²⁺ to Ca²⁺ ratio ranging from 1·30 to 1·66 during irrigation period. The application of phosphogypsum increased Ca²⁺ concentration in the soil and triggered the replacement of excess Mg²⁺ from the cation exchange complex. After harvesting the first crop, there was 18 per cent decrease in exchangeable magnesium percentage (EMP) of the surface 0·2 m soil over the pre‐experiment EMP level in the plots where phosphogypsum was applied at 4·5 t ha⁻¹, and a 31 per cent decrease in EMP in plots treated with phosphogypsum at 8 t ha⁻¹. Additional beneficial effect of the amendment was an increase in the soil phosphorus content. The 4‐year average cotton yields were 2·6 t ha⁻¹ with 8 t ha⁻¹ phosphogypsum, 2·4 t ha⁻¹ with 4·5 t ha⁻¹ phosphogypsum, and 1·4 t ha⁻¹ with the control. Since the amendment was applied once at the beginning, exchangeable Mg²⁺ levels tended to increase 4 years after its application, particularly in the treatment with 4·5 t ha⁻¹ phosphogypsum. Thus, there would be a need for phosphogypsum application to such soils after every 4–5 years to optimize the ionic balance and sustain higher levels of cotton production. The economic benefits from the phosphogypsum treatments were almost twice those from the control. Copyright © 2007 John Wiley & Sons, Ltd.     

The effect of land management on carbon and nitrogen status in plants and soils of alpine meadows on the Tibetan plateau

Large‐scale grassland rehabilitation has been carried out on the severely degraded lands of the Tibetan plateau. The grasslands created provide a useful model for evaluating the recovery of ecosystem properties. The purposes of this research were: (1) to examine the relative influence of various rehabilitation practices on carbon and nitrogen in plants and soils in early secondary succession; and (2) to evaluate the degree to which severely degraded grassland altered plant and soil properties relative to the non‐disturbed native community. The results showed: (1) The aboveground tissue C and N content in the control were 105·97 g m⁻² and 3·356 g m⁻², respectively. The aboveground tissue C content in the mixed seed treatment, the single seed treatment, the natural recovery treatment and the severely degraded treatment was 137 per cent, 98 per cent, 49 per cent and 38 per cent, respectively, of that in the control. The corresponding aboveground tissue N content was 109 per cent, 84 per cent, 60 per cent and 47 per cent, respectively, of that in the control. (2) Root C and N content in 0–20 cm depths of the control had an average 1606 g m⁻² and 30·36 g m⁻², respectively. Root C and N content in the rehabilitation treatments were in the range of 26–36 per cent and 35–53 per cent, while those in the severely degraded treatment were only 17 per cent and 26 per cent of that in the control. (3) In the control the average soil C and N content at 0–20 cm was 11 307 g m⁻² and 846 g m⁻², respectively. Soil C content in the uppermost 20 cm in the seeded treatments, the natural recovery treatment and the severely degraded treatment was 67 per cent, 73 per cent and 57 per cent, respectively, while soil N content in the uppermost 20 cm was 72 per cent, 82 per cent and 79 per cent, respectively, of that in the control. The severely degraded land was a major C source. Restoring the severely degraded lands to perennial vegetation was an alternative approach to sequestering C in former degraded systems. N was a limiting factor in seeding grassland. It is necessary for sustainable utilization of seeding grassland to supply extra N fertilizer to the soil or to add legume species into the seed mix. Copyright © 2005 John Wiley & Sons, Ltd.     

Evaluation of alternative approaches to rainforest restoration on abandoned pasturelands in tropical North Queensland,Australia

The lag time for natural recruitment of tropical rainforest species in abandoned pastureland is very long, therefore artificial restoration techniques have been employed to accelerate natural seedling recruitment. The objectives of this study were to investigate: (1) the success/failure of establishment 502 seedlings belonging to 15 species from 11 families planted approximately ten years ago; and (2) the influence of different restoration techniques on enhancing natural recruitment during this period. The study was conducted in the wet tropical rainforest region of northeast Queensland, Australia as a completely randomized block design involving five treatments with two replicates. In each plot, 63 tropical rainforest seedlings from one or a combination of species were planted randomly. Two control plots were laid out where no seedlings were planted. Survival, height and diameter data were taken on the seedlings ten years after planting. Each 11×17 m² plot was further divided into 187, 1×1 m² subplots. Within each subplot all seedlings recruited were located and identified. Canopy cover was estimated using belt transects 1 m apart that ran in an east–west direction across the plots. Within each plot the percentage of grass, and the crown cover were estimated using the Braun‐Blanquet cover abundance scale. Survival rate of planted seedlings varied across the treatment plots. The survival rate ranged from 65 to 75 per cent for primary‐promoter species, 85 to 100 per cent in middle‐phase species and 42 to 57 per cent for mature‐phase species. No Pilidiostigma tropicum seedlings survived in any treatment. Fourteen species recruited naturally across the treatment plots. A total of 410 seedlings were naturally recruited from 11 different families in the ten‐year‐old reforested site. The highest natural recruitment (236 seedlings) occurred in Treatment 3, where Omalanthus novo‐guineensis seedlings were planted with eight primary‐promoter species, followed by 99 in Treatment 5 where a group of primary‐promoters, middle phase species and mature‐phase species were planted together, 36 in Treatment 4 (Alphitonia petriei planted with eight primary‐promoter species), 10 in Treatment 2 where only Omalanthus novo‐guineensis seedlings were planted, and 13 in control plots. Grass cover declined with increasing species diversity and increased canopy cover. The results indicate that the diversity of species used in restoration had a major influence on natural recruitment. Copyright © 2004 John Wiley & Sons, Ltd.     

Seedbank phytosociology of the Strandveld Succulent Karoo,South Africa: a pre‐mining benchmark survey for rehabilitation

Prior to the mining of heavy minerals, the seedbank of the Strandveld Succulent Karoo was investigated to serve as a benchmark for the future rehabilitation of the area. Seedbank composition and species' abundance were determined with the seedling emergence method. By using the Braun‐Blanquet method, five main vegetation units were identified in concordance with results obtained for the standing vegetation. A total of 108 species were recorded in the seedbank, which represents c. 50 per cent of the species recorded in the standing vegetation of the total study area. Seven annual species (3 per cent) were unique to the soil seedbank. On community level, similarity in species composition between the standing vegetation and the soil seedbank ranged between 39·2 per cent and 48·8 per cent, with a similarity of 54·3 per cent for the total study area. Annual and perennial species' similarity in species composition between the standing vegetation and the seed bank totalled 74·8 per cent and 43·1 per cent respectively. Post‐mining topsoil replacement as well as seeding and transplanting of selected local species will be essential to revegetate this area. Copyright © 2001 John Wiley & Sons, Ltd.     

Physical properties of some intensively cultivated soils of Ireland amended with spent mushroom compost

In this paper, spent mushroom compost (SMC), a by‐product of the mushroom industry, is proposed as a suitable organic amendment for soil structure restoration. A 4‐month incubation pot trial was conducted in which fresh and composted SMC was amended at three different rates (50, 100 and 200 t ha⁻¹) to a range of structurally degraded tillage soils (n = 10). Soil OC content and aggregate stability as determined by the three disrupting tests of the Le Bissonnais method (fast‐wetting, slow‐wetting and mechanical breakdown) were investigated. Applications of 50, 100 and 200 t ha⁻¹ fresh SMC increased the OC content by 2·71 per cent, 2·69 per cent and 2·49 per cent respectively, while amendments of composted SMC increased the OC content by 3·28 per cent, 2·94 per cent and 2·87 per cent for each application rate, respectively. The effect of SMC on aggregate stability was generally positive and statistically significant in most soils. However, in soils 3 and 4 an application rate of 200 t ha⁻¹ SMC decreased the aggregate stability, on average, by 15 per cent, in comparison to the control, for the fast‐wetting test. Aggregate stability was strongly controlled by the inherent OC content of the study soils; that is, the OC content prior to SMC addition. A positive correlation coefficient was also evident for the dithionite‐extractable iron, most pronounced for slow‐wetting and mechanical breakdown treatments (r = 0·844 and r = 0·817 respectively). It is clear from this research that SMC amendments have the capacity to improve soil structural stability. Copyright © 2007 John Wiley & Sons, Ltd.     

Plasticity of high and low nutrient‐adapted grasses to added sulfur and nitrogen

Crop and native plants can be characterized as high and low nutrient‐adapted based on their expected response to native and applied nutrients. Our objective was to compare the plasticity of biomass allocation and tissue nutrient concentrations to added sulfur (S) and nitrogen (N) across a continuum of high and low nutrient‐adapted grasses, represented by barley (Hordeum vulgare), smooth brome (Bromus inermis), bluebunch wheatgrass (Pseudoroegneria spicata), and Idaho fescue (Festuca idahoensis). In our greenhouse study, treatments included two S sources (pyrite and gypsum), at 150 and 300 kg S ha^‐1, N at 50 kg ha^‐1, and a check. Shoot biomass of barley, smooth brome, and bluebunch wheatgrass was enhanced by S plus N. Shoot biomass of barley and smooth brome was greater with pyrite than with gypsum. Root biomass of smooth brome and bluebunch wheatgrass was greater with pyrite than with gypsum. Plant S concentrations of barley and Idaho fescue were enhanced by added S. Plant S concentrations in barley and smooth brome were greater with gypsum than with pyrite. Except for barley, plant S pools (shoot biomass x shoot S concentration) were enhanced with S plus N compared with no added nutrients. Nitrogen pools of barley, smooth brome, and bluebunch wheatgrass were higher with pyrite than with gypsum. Soil sulfate (SO₄) was greater when S or S plus N was added than without any added nutrients. For barley and smooth brome, soil sulfate tended to be lower with pyrite than with gypsum. For all soils, pH was lower with added S or added S plus N compared with unamended soils. While pyrite lowered soil pH, gypsum tended to increase soil pH. Overall, barley and smooth brome were highly plastic in responding to enhanced nutrient levels, bluebunch wheatgrass was relatively responsive, and Idaho fescue was least responsive.     

Phosphorus acquisition and wheat growth are influenced by shoot phosphorus status and soil phosphorus distribution in a split‐root system

Root proliferation and greater uptake per unit of root in the nutrient‐rich zones are often considered to be compensatory responses. This study aimed to examine the influence of plant phosphorus (P) status and P distribution in the root zone on root P acquisition and root and shoot growth of wheat (Triticum aestivum L.) in a split‐root soil culture. One compartment (A) was supplied with either 4 or 14 mg P (kg soil)^–1, whereas the adjoining compartment (B) had 4 mg P kg^–1 with a vertical high‐P strip (44 mg kg^–1) at 90–110 mm from the plant. Three weeks after growing in the split‐root system, plants with 4 mg P kg^–1 (low‐P plants) started to show stimulatory root growth in the high‐P strip. Two weeks later, root dry weight and length density in the high‐P strip were significantly greater for the low‐P plants than for the plants with 14 mg P (kg soil)^–1. However, after 8 weeks of growth in the split‐root system, the two P treatments of compartment A had similar root growth in the high‐P strip of compartment B. The study also showed that shoot P concentrations in the low‐P plants were 0.6–0.8 mg g^–1 compared with 1.7–1.9 mg g^–1 in the 14 mg P kg^–1 plants after 3 and 5 weeks of growth, but were similar (1.1–1.4 mg g^–1) between the two plants by week 8. The low‐P plants had lower root P concentration in both compartments than those with 14 mg P kg^–1 throughout the three harvests. The findings may indicate that root proliferation and P acquisition under heterogeneous conditions are influenced by shoot P status (internal) and soil P distribution (external). There were no differences in the total root and shoot dry weight between the two P treatments at weeks 3 and 5 because enhanced root growth and P uptake in the high‐P strip by the low‐P plants were compensated by reduced root growth elsewhere. In contrast, total plant growth and total root and shoot P contents were greater in the 14 mg P kg^–1 soil than in the low‐P soil at week 8. The two P treatments did not affect the ratio of root to shoot dry weight with time. The results suggest that root proliferation and greater P uptake in the P‐enriched zone may meet the demand for P by P‐deficient plants only for a limited period of time.     

Soil degradation by Erosion of a typic hapludalf in central Ohio and its rehabilitation

Soil erosion and runoff were monitored from 1988 to 1990 on a Miamian soil (Typic Hapludalf) of 5-6 per cent slope using field runoff plots. Four treatments were studied: (i) disk-plough up and down the slope to 0.3 m depth (DP); (ii) disk-plough up and down the slope followed by a protective netting (PN); (iii) uncultivated fallow without any vegetation followed by surface soil removal (R); (iv) uncultivated fallow with natural vegetation followed by ploughing (F). Mean annual runoff losses were 6, 114 and 128 mm, or 4, 20 and 18 per cent of the rainfall, and mean annual soil losses were 1.2, 85.0 and 64.0 Mg ha⁻¹ in 1988, 1989 and 1990, respectively. Mean runoff amounts were 26, 69, 116 and 118mm and mean annual soil losses were 0.4, 23.2, 58.6 and 118 Mg ha⁻¹ for the F, PN, DP and R treatments, respectively. In comparison with DP, PN decreased annual runoff by 40.3 per cent and annual soil loss by 79.5 per cent. The high mean soil loss for the R treatment was due to erosion following soil removal. An additional 2920 Mg ha⁻¹ of surface soil was removed from the R treatment in May 1990. The F treatment reduced runoff by 78, 77 and 62 per cent and reduced soil loss by 99.7, 99.4 and 98.4 per cent compared with the R, DP and PN treatments, respectively. Mean losses of K, Ca, Mg and P were 1.3, 4, 1 and 01 kg ha⁻¹, respectively for F, 3, 16, 5 and 0.3kg ha⁻¹, respectively, for PN, 5, 31, 1 and 0.6kg ha⁻¹, respectively, for DP, and 3, 32, 12 and 0.4 kg ha⁻¹, respectively, for R. Soil and nutrient losses for each treatment were in the order R > DP > PN > F. The soil organic carbon (SOC) content was significantly affected by soil erosion and management treatments, and ranged from 0.98 per cent for the R treatment to 2.3 per cent for the F treatment. Soil surface removal for the R treatment in 1990 reduced water-stable aggregates (WSA) by 9.0 per cent, SOC by 0.6 per cent, and clay content of the uppermost 0-50 mm depth by about 7.0 per cent. Mean total porosity (f_t) ranged from 0.43 for the F to 0.52 for the DP treatment. Cumulative infiltration for 3h ranged from 13 cm for R to 34cm for PN, with corresponding infiltration rates of 4 cm h⁻¹ and 13 cm h⁻¹, respectively. Regardless of the treatment, there were also temporal changes in soil properties. In comparison with 1988, measurements made in 1990 showed a significant decrease in WSA of 21.3 per cent, an increase in clay content of 2.8 per cent, and a decrease in SOC of 0.39 per cent. Runoff and soil losses were significantly correlated with the mean weight diameter (MWD), SOC, bulk density (p_b) and available water capacity (AWC). Plant height measured 8 weeks after planting (WAP) for the R treatment was reduced by 33.3 per cent, 33.0 per cent and 29.0 per cent compared withh DP, PN and F, respectively. Nitrogen uptake by maize plants (Zea mays L.) 10 WAP for the R treatment was lower by 15 per cent, 8 per cent, and 6 per cent compared with the DP, PN and F treatments, respectively, while P uptake was lower by 33 per cent, 32 per cent and 29 per cent, respectively, compared with the same treatments. Grain yield was 9.78 Mg ha⁻¹ for PN, 9.76 Mg ha⁻¹ for DP, 8.64 Mg ha⁻¹ for F and 6.60 Mg ha⁻¹ for R during the 1990 crop season. Grain yield was reduced by about 32.4 per cent in the R treatment compared with the PN treatment, representing a maize grain yield reduction of 158 kg ha⁻¹ for each centimeter of soil lost.     

REVEGETATION OF DECOMPOSED GRANITE ROADCUTS IN KOREA: DEVELOPING DIGGER,EVALUATING COST EFFECTIVENESS,AND DETERMINING DIMENSIONS OF DRILLING HOLES,REVEGETATION SPECIES,AND MULCHING TREATMENT

Decomposed granite roadcuts are difficult to revegetate after losing the topsoil and vegetation cover. We developed a new drilling machine, Digger, to efficiently drill six holes simultaneously on decomposed granite roadcuts to facilitate revegetation. The Digger consists of a base machine (0.7 m³‐level excavator) and a mounting body with six hydraulic motors instead of a bucket. We tested its performance on two roadcuts in southwest Korea using time‐motion studies, which showed that the Digger can drill 240 m² of decomposed granite roadcuts daily. The unit cost of the Digger was less than a half of other roadcut stabilization and revegetation techniques in Korea, making the Digger a cost‐effective revegetation technology. Field germination and growth tests were also conducted to identify appropriate diameter and depth of drilling holes, suitable revegetation species, and mulching treatment. We drilled holes with three different diameters and depths, filled the holes with a mixture of plant seeds and cultivated soil, applied mulching treatments (coir geotextile, shade net, and no mulching), and measured the germination and growth results at two field plots after 1 month and 1 year. The results showed that drilling diameter 10 cm and depth 10 cm were large enough to result in better plant germination and growth. Erosion control species, Poa pratensis L. and Eragrostis curvula (Schrad.) Nees, survived and grew better than native woody species. Coir geotextile improved the plant germination and growth. The time‐motion and revegetation results show that the Digger can be a promising technology to restore decomposed granite roadcuts. Copyright © 2013 John Wiley & Sons, Ltd.     

Cover crop nitrogen availability to conventional and no‐till corn: Soil mineral nitrogen,corn nitrogen status,and corn yield

Abstract

Understanding seasonal soil nitrogen (N) availability patterns is necessary to assess corn (Zea mays L.) N needs following winter cover cropping. Therefore, a field study was initiated to track N availability for corn in conventional and no‐till systems and to determine the accuracy of several methods for assessing and predicting N availability for corn grown in cover crop systems. The experimental design was a systematic split‐split plot with fallow, hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), wheat (Triticum aestivum L.), rye+hairy vetch, and wheat+hairy vetch established as main plots and managed for conventional till and no‐till corn (split plots) to provide a range of soil N availability. The split‐split plot treatment was sidedressed with fertilizer N to give five N rates ranging from 0–300 kg N ha^‐1 in 75 kg N ha^‐1 increments. Soil and corn were sampled throughout the growing season in the 0 kg N ha^‐1 check plots and corn grain yields were determined in all plots. Plant‐available N was greater following cover crops that contained hairy vetch, but tillage had no consistent affect on N availability. Corn grain yields were higher following hairy vetch with or without supplemental fertilizer N and averaged 11.6 Mg ha^‐1 and 9.9 Mg ha^‐1 following cover crops with and without hairy vetch, respectively. All cover crop by tillage treatment combinations responded to fertilizer N rate both years, but the presence of hairy vetch seldom reduced predicted fertilizer N need. Instead, hairy vetch in monoculture or biculture seemed to add to corn yield potential by an average of about 1.7 Mg ha^‐1 (averaged over fertilizer N rates). Cover crop N contributions to corn varied considerably, likely due to cover crop N content and C:N ratio, residue management, climate, soil type, and the method used to assess and assign an N credit. The pre‐sidedress soil nitrate test (PSNT) accurately predicted fertilizer N responsive and N nonresponsive cover crop‐corn systems, but inorganic soil N concentrations within the PSNT critical inorganic soil N concentration range were not detected in this study.     

Nitrogen requirements associated with improved conservation tillage for corn production

Abstract

Excessive soil erosion and use of nitrogen fertilizer are costly to the Atlantic Coastal Plain corn (zea mays L., ’Funks G 4507') producer and both may serve to create environmental hazards. An in‐row chisel (36 cm deep) tillage method was compared with the standard 5 cm fluted coulter method for planting corn in premature wheat (Triticim aestivum L.) residues grown on an Orangeburg sandy loam (Typic Paleudult). Five orthogonal N levels ranging up to 440 kg of N/ha were used to determine an economic N optimum for each tillage method.

The in‐row chisel tillage method provides a possible yield advantage in the Atlantic Coastal Plain because of observed restricting soil layers within the normal corn rooting zone. The estimated profit‐maximizing quantities of N fertilizer were 262 and 295 kg of N/ha (234 and 263 1b of N/acre) for the fluted coulter and in‐row tillage procedures, respectively. Corn grain yields associated with these inputs were 9.6 × 10³ and 12.6 × 10³ kg/ha (153 and 200 bu/acre), respectively. The yield increase associated with in‐row chiseling through a 2.5 metric ton mulched surface is attributed to potentially improved rooting and more efficient water storage and use.