Abstract The kinetics of Pb sorption were investigated on clay (silty clay, Torrifluvents), CaCO3‐rich (sandy clay, Calciorthids), and sandy (sandy loam, Quartzipasmments) soils at two different temperatures. Equilibrium in Pb sorption was attained in 2, 12, and 24 h for CaCO3‐rich, sandy, and clay soils, respectively. The kinetics of Pb sorption were evaluated using Elovich, modified Freundlich, parabolic diffusion, and first‐order equations. The first‐order equation adequately described the kinetics of Pb sorption for all the soils, temperatures, and initial concentrations used. The choice of the first‐order equation among the others investigated was based on the lower standard error of estimate (SE) obtained and on the more realistic assumptions of the equation. The sorption rate coefficient (k a) values, at 298 K, ranged from 1.46 × 10‐3 to 6.58 × 10‐3 min‐1 in the sandy soil, from 2.42 × 10‐3 to 11.72 × 10‐3 min‐1 in the clay soil, and from 33.16 × 10‐3 to 58.42 × 10‐3 min‐1 in the CaCO3‐rich soil. T...

Resumen Se ha estudiado la pérdida de peso en el proceso de descomposición de hojarasca en tres ecosistemas forestales de la zona semiárida Cuenca del Duero: un encinar climácico de Quercus rotundifolia Lam., un pinar paraclimácico de Pinus pinea L., y un pinar disclimácico de P. pinaster Ait. No se encuentran diferencias significativas entre la dinámica de descomposición de las hojas en cada ecosistema, salvo cuando las hojas de encina se colocan en otros ecosistemas. La pérdida de peso se ajusta a una curva exponencial negativa. En todos los casos, durante los cuatro primeros meses de experimentación, el peso original se reduce en un 30%. Ello parece indicar que es la climatología quien dirige fundamentalmente, a corto plazo, el proceso de descomposición. En condiciones naturales, los índices de descomposición (K j y K o) siguen la secuencia: encina > pino piñonero > pino marítimo, tanto en hojas como en hojarasca total.

Abstract The availability of N, P, K, and organic‐C content of soil at 0‐ to 15‐, 15‐to 30‐, and 30‐ to 45‐cm depths were estimated in a long‐term field experiment testing farmyard manure and fertilizer‐N doses in a pearl millet‐wheat cropping sequence. Application of farmyard manure increased available P, K, and organic‐C content of soil at all depths and doses of fertilizer‐N. Available N content decreased from its original content (100 mg N kg‐1) with the application of farmyard manure as well as fertilizer‐N due to cropping of pearl millet and wheat crops during the last 20 years. Application of increasing doses of fertilizer‐N had very little effect on available P, K, and organic‐C content of soil; however, available N increased significantly (p = 0.05). Available P, K, and organic‐C content of soil can be maintained to their original contents with the application of 8.2, 2.4, and 7.5 Mg farmyard manure ha‐1 year‐1, respectively, along with 120 kg N ha‐1.

Abstract A laboratory sprinkler (rain) infiltration experiment was carried out on long stratified columns of sandy soil (Typic Torripsamments) packed to 1.50 g cm‐3 bulk density to investigate the effect of gel‐forming conditioner (Jalma) on wetting front advance Z, water distribution, and redistribution profiles under different sprinkler intensities I using a simple sprinkler simulator. Five concentrations of Jalma J, 0.0, 0.25, 0.50, 0.75, and 1.0% (on dry weight basis), were uniformly applied to the upper layer (10‐cm depth) at three sprinkler intensities of 1.25, 2.25, and 3.25 cm h‐1. The time required for the wetting front to reach 10‐cm depth t° was significantly increased either by increasing J added to the upper layer or decreasing I applied on soil surface. However, the treatment of 1% J caused surface ponding before Z had advanced to 10‐cm depth for the three values of I. A fairly uniform water profile was produced in the homogeneous soil (J = 0%), and the constant water content as fractional volume θT was found equal to the ratio of the sprinkler intensity I to the velocity of the wetting front v. Addition of Jalma to the upper layer increased the water content in that layer, which was magnified by increasing I, but did not affect the value of θT in the untreated lower layer. The higher water content observed at the soil surface due to Jalma application never approached the corresponding value of the saturation water content θs under sprinkler infiltration. The experimental results revealed that the water movement in the untreated lower layer was unaffected by Jalma applied to the treated upper layer. Equations based on Darcy's law along with the physical properties of the resulted water distribution profile were derived to compute Z and θT under sprinkler infiltration as affected by Jalma applied to the upper layer of sandy soil. The development of water redistribution profiles indicated that the amount of water retained in the treated upper layer was much higher than that in the untreated upper and lower layers at the same corresponding redistribution times and sprinkler intensity. However, the same uniform water content θT, which was associated with —10 kPa matric potential on average, was approximately achieved in the untreated lower layer 3 days after sprinkler infiltration regardless of Jalma applied to the treated upper layer. In general, the study may suggest application of Jalma conditioner at 0.75% to the upper layer (10‐cm depth) of sandy soil under medium sprinkler intensity I around 2 cm h‐1 and a wetted depth not more than 20 cm for the benefit of water use efficiency.

Abstract Surface (0–15 cm) soil samples (906) collected from arid and semi‐arid regions of the Punjab state, India, were analyzed for DTPA‐(diethylenetriaminepentaacetic acid) extractable micronutrient cations of Zn, Fe, Mn, and Cu, and other soil properties. The textural classes of soils were loamy sand, sandy loam, and loam. The majority of soils were free of any salt problems and their pH values ranged from 7.0 to 10.5. The content of DTPA‐extractable Fe, Mn, and Cu was directly related to soil texture. The finer the texture, the higher was the content of these micronutrients. There was a significant positive correlation between soil organic carbon and DTPA‐extractable micronutrients. Polynomial regressions of 1st to 3rd degree best defined the relationship between soil organic carbon and DTPA‐extractable ions. In these arid and semiarid soils, the micronutrient cations are likely to constrain crop production in coarse‐textured soils having low levels of soil organic carbon.

Abstract Sodic soil reclamation requires replacing exchangeable Na+ with Ca2+ and leaching the excess Na+ from the soil. Cottage cheese whey has an electrical conductivity (EC) of 6–10 dS m‐1, pH values of 4.2 or less, low sodium adsorption ratios (SAR), and contains 40–50 g kg‐1 of readily decomposable organic matter. These whey characteristics should all be beneficial in reclaiming sodic soils. This study was conducted to determine the effects of cottage cheese whey on the chemical and physical properties of a sodic soil (SAR = 16.3, ECe = 3.8, and pH 8.3). Cottage cheese whey was applied to 300‐mm‐deep sodic soil columns at 0‐, 20‐, 40‐, and 80‐mm rates followed by 80, 60, 40, and 0 mm of distilled water, respectively. The columns were then incubated at 10°C for 21 days, and then leached until 96 mm (0.60 pore volumes) of leachate was collected. All whey applications lowered the soil pH, SAR, and exchangeable sodium percentage (ESP) in both the upper and lower 150‐mm‐depth increments. Aggregate stability in the surface 150‐mm‐depth increment increased from 11% in the water‐leached soil to 22% in the 80‐mm whey‐treated soil. The results of this study suggest that cottage cheese whey can be used as an effective sodic soil amendment.

Abstract Soil disturbance by livestock hooves and by mechanical cultivation has been suggested as a way to increase soil water intake on crusted rangeland soils. In conjunction with a seedling establishment study on a sandy loam soil in southern Arizona, soil water content and temperature were measured continuously for the 1988 and 1989 summer rainy seasons on seedbeds that were one‐time intensively trampled by cattle, furrowed with a land imprinter, or left undisturbed. Diurnal surface temperatures (1‐cm depth) fluctuated up to 31°C even when surface soils were wet. Maximum temperatures were lowest at the basin or bottom and highest on the south‐facing slope of the imprint furrows. Soils disturbed by trampling or imprinting wet up more (had a higher maximum water content) than undisturbed soils after summer rains in mid July to early August, but wet up less than undisturbed soils near the end of the rainy season, presumably due to reformation of the surface crust. Increased wetting of trampled or imprinted soils compared to undisturbed soils resulted in longer periods of soil water availability after some storms at some depths. Slightly longer periods of surface soil water availability (1–2 days at 1–3 cm deep) were associated with greater emergence of seeded grasses on trampled and imprinted soils than on undisturbed soils in 1988. Two periods of surface soil water availability of 5–7 days long separated by a dry period of 6–33 h long in July 1988 were associated with successful grass seedling emergence, while available water periods of only 2–3.5 days in July 1989 were associated with limited seedling emergence. One‐time heavy trampling by cattle and land imprinting could be expected to temporarily increase soil water availability and seedling emergence of seeded species on similar soils during some years. These treatments should not be expected to greatly increase the time of soil water availability or ensure revegetation success during dry years.

Abstract Plants of Hedysarum confertum Desf. and Hedysarum spinosissimum L. inoculated with five Glomus species (G. epigaeum, G. etunicatum, G. fasciculatum, G. macrocarpum and G. mosseae) were grown in a marl soil for 14 weeks. Both legumes became colonized with VAM fungi, although colonization percentages were lower than those observed in nature. For H. confertum, G. epigaeum, G. fasciculatum, and G. macrocarpum increased growth significantly when compared to controls. For H. spinosissimum the most efficient fungi for growth improvement were G. macrocarpum, G. mosseae, and G. etunicatum. A clear growth‐depressing effect of G. fasciculatum on H. spinosissimum was observed. Root/shoot ratio increases with inoculation in H. confertum but can decrease in H. spinosissimum. P uptake was not markedly improved by mycorrhizal inoculation. The greatest amounts of P occurred in both legumes colonized by G. macrocarpum.