Deschampsia cespitosa subalpine tussockland on the Green Lake landslide, Hunter Mountains, Fiord Ecological Region, New Zealand

The continuous use of heavy machinery and vehicular traffic on agricultural land led to an increase in soil compaction, which reduces crop yield and deteriorates the physical conditions of the soil. A pot experiment was conducted under greenhouse conditions to study the effects of induced soil compaction on growth and yield of two wheat (Triticum aestivum) varieties grown under two different soil textures, sandy loam and sandy clay loam. Three compaction levels [C0, C1, and C2 (0, 10 and 20 beatings)], two textural classes (sandy loam and sandy clay loam), and two genotypes of wheat were selected for the experiment. Results indicated that induced soil compaction adversely affected the bulk density (BD) and total porosity of soil in both sandy loam and sandy clay loam soils. Compaction progressively increased soil BD from 1.19 Mg m−3 in the control to 1.27 Mg m−3 in C1 and 1.40 Mg m−3 in C2 in sandy loam soil while the corresponding increase in BD in sandy clay loam was 1.56 Mg m−3 in C1 and 1.73 Mg m−3 in C2 compared to 1.24 Mg m−3 in the control. On the other hand, compaction tended to decrease total porosity of soil. In case of sandy loam, porosity declined by 5% and 17% in C1 and C2, respectively, and declined in sandy clay loam by 29% and 54%, respectively. Averaged over genotypes and textures, shoot length decreased by 15% and 26% at C1 and C2, respectively, and straw yield decreased by 21% and 61%, respectively. The compaction levels C1 and C2 significantly decreased grain yield by 12% and 41%, respectively, over the control. The deleterious effect of compaction was more pronounced on root elongation and root mass, and compaction levels C1 and C2 decreased root length by 47% and 95% and root mass by 41% and 114%, respectively, over the control. Response of soil texture to compaction was significant for almost all the parameters, and the detrimental effects of soil compaction were greater in sandy clay loam compared to sandy loam soil. The results from the experiment revealed that soil compaction adversely affected soil physical conditions, thereby restricting the root growth, which in turn may affect the whole plant growth and grain yield. Therefore, appropriate measures to avoid damaging effects of compaction on soil physical conditions should be practiced. These measures may include soil management by periodic chiseling, controlled traffic, conservation tillage, addition of organic manures, and incorporating crops with deep tap root systems in a rotation cycle.

Soybean is a good source of protein and calories and therefore important for food security. Soybean yields in small scale farmers field stand at less than 1.0 t ha-1 against a potential of 3 to 3.6 t ha-1. This has been attributed to low soil fertility. Although a lot of work has been carried out on Soybean nitrogen (N) and phosphorus (P) nutrition, but research findings indicate that yields are still low, raising suspicion that other nutrients could also be limiting. To investigate this, a nutrient omission trial was used in the greenhouse to find out the nutrients that limit soybean production in four distinct soil textures - clay loam, sandy clay loam, sandy clay and sandy loam following the recommended rate of 20:40:20:5:20 Kg/ha for N,P,K,Zn, and S respectively. Similarly we applied 1 ton/ha of poultry manure with thirty six treatments combinations arranged in a completely randomized design. The results revealed that soybean performance and nutrient uptake varied significantly (p<0.05) between the soil texture andnutrients application. Sandy clay loam and sandy loam textures respond significantly to nitrogen, phosphorus, potassium and manure application whereas zinc and NPK nutrients limits soybean performance and uptake in sandy clay and clay loam soils. In conclusion, to increase soybean production in sandy loam and clay loam of Sudan savanna of Nigeria, fertilizer formulations containing N, P, K and Zn should be used. Manure may be used to improve soybean production in sandy clay and sandy clay loam together with application of NPK fertilizer.

Spatial variability mapping of soil properties is essential to understand the differences among soils found in a geographical region for their better management. This study aimed at spatial variability mapping of selected soil properties of district Tando Allahyar, Sindh which is one of the most important districts of Sindh province. The results revealed that majority of soils (35.6%) had loamy slightly medium-textured type, including 30.8% silt loam, 3.8% loam and 1.0% silt, followed by clayey, fine-textured heavy type (27.9%), including 18.3% clay, 6.7% silty clay and 2.9% sandy clay. Soils with sandy, coarse-textured light type were 20.2%, including 16.3% sandy loam and 1.9% loamy sand and sand each. Soils with loamy, moderately medium-textured type were 16.3%, including 9.6% clay loam and 6.7% sandy clay loam, while silty clay loam soil texture was total missing. The EC ranged from 0.14 to 4.44 dS m-1 (mean: 0.69 dS m-1, mode: 0.42 dS m-1). Majority (91%) of soils had low (46%) to medium (45) level of salinity. Soil pH ranged from 6.2 to 8.6 (mean: 7.7, mode: 8.3). Majority of soils (84%) had either slightly (24%), medium (22%) or strongly alkaline (38%) soil pH. Interestingly, some soils (13%) had slightly acidic pH. Organic matter ranged from 0.10 to 1.6% (mean: 0.64%, mode: 0.17%). Majority (84%) of soils were deficient in organic matter. Soil ABDTPA-P ranged from 1.2 to 18.8 mg kg-1 (mean: 5.38 mg kg-1, mode: 2.4 mg kg-1). More than half (55%) of the soils had low P, while soils with marginal (14%) or adequate (31%) P were also present. Soil ABDTPA-K ranged from 31 to 376 mg kg-1 (mean: 154 mg kg-1, mode: 230 mg kg-1). Majority of soils (62%) had adequate K, while soils with marginal (28%) or low (11%) K were also found. Spatial variability mapping revealed the dominance of loam, sandy clay loam, sandy loam, silty clay and clay loam textures, medium > low and high > salinity, slightly to medium alkaline soils > strongly alkaline soils, low organic matter content, medium to adequate > low soil P, and adequate soil K. The spatial variation found in various soil properties of district Tando Allahyar, Sindh must be taken in mind while deciding about their site-specific management, using the recently developed maps.

Accurate evaluation of the soil water reserves available for plant use is vital in developing optimum water management for crop production in marginally dry regions. Laboratory estimates of the upper and lower limits of soil water availability used to calculate the soil water reservoir often deviate significantly from the limits measured in the field. To make a unified and broad assessment of the accuracy of laboratory measurements for estimating field soil water, we obtained and evaluated a comprehensive data base of field‐measured upper and lower limits of the soil water reservoir. The field‐measured upper limit was taken as the water content at which drainage from a prewetted soil had practically ceased. The lower limit was taken as the water content of the soil at which plants were practically dead or dormant as a result of the soil water deficit. These field‐measured limits were compared to laboratory measurements at −0.33 and −15 bar made on samples removed from each field site. A total of 401 observations were available for the comparisons of −15 bar measurements to the field‐measured lower limits and 282 observations of −0.33 bar measurements were available for comparison with the field‐measured upper limit. Variation often existed within a soil series at a particular site for the field‐measured upper and lower limits. However, the differences between the field‐measured limits, the total available water reservoir, were relatively constant. Crop species caused only minor differences in the lower limit water content for the upper part of the soil profile where root length density was apparently above some critical limit. However, some annuals extracted water to greater depths than others. The laboratory estimates of the upper limit obtained by −0.33 bar water contents were significantly less than the field‐measured drained upper limit for sands, sandy loams, and sandy clay loams and were significantly more than field measurements for silt loams, silty clay loams, and silty clays. The laboratory estimates of the lower limit obtained by −15 bar water content measurements were significantly less than field lower limit measurements for sands, silt loams, and sandy clay loams and significantly more than field observations for loams, silty clays, and clays. Because our study included relatively few measurements of loamy sands, silts, sandy clays, and clays, it was difficult to generalize about differences in field‐measured and laboratory‐estimated water limits for those textures. The results suggest that if absolute accuracy is necessary in water balance calculations, laboratory‐estimated soil water limits should be used with caution and field‐measured limits, if available, would be preferred.

Stress relaxation of five different soil samples when uniaxially compacted at different water contents

Mapping fine scale spatial variations of soil properties is important for site specific agriculture. The current study explores the potentials of remote sensing (RS) and geographical information system (GIS) techniques in studying the spatial variability of surface soil attributes. Around 170 surface (0–30 cm) soil samples collected from the soils of Shorkot Tehsil, Punjab, Pakistan were analyzed for surface soil texture and organic matter (O.M.). A multivariate linear regression (MLR) analysis technique was employed to relate surface soil variables with the spectral data from Landsat TM5 satellite. The MLR analysis showed significant (p<0.05) relationship of band 4 and band 6 with silt% (R2 = 0.724) and clay% (R2 = 0.509) while soil O.M. was best modeled using data from band 1, 6 and 7 (R2 = 0.545). The resulting MLR equations were then used for the spatial modeling of these attributes for the entire study area. For developing surface soil texture map, the USDA textural triangle limits for clay% and silt% were used to develop a code in Visual Basic Language in ArcGIS environment. The results showed that ‘sandy clay loam’ was the most abundant textural class in the area followed by ‘sandy loam’ and ‘clay loam’ classes. Moreover, the status of O.M. in the entire study area soils was very poor (<1%). The results indicate that RS and GIS techniques could be successfully used for fine scale mapping of soil texture and O.M. of a larger area.

Mineralogy of fadama soils of southern Taraba state was carried alongside its influence on the soil’s physical and chemical properties. The three local government areas selected for this study were Ibi, Wukari and Donga. The mineralogical compositions of the soils were evaluated using the clay fraction. X- ray diffraction (XRD) analysis showed ibi had quartz (21%), microcline (47%) and kaolinite (25%), Wukari Tsukundi had quartz (17%), microcline (20%) and kaolinite (32%), phlogopite (15.4%) and gibbsite (23%) while Donga had mineral composition of quartz (20%), microcline (33%) and kaolinite (47%) and therefore the clay minerals are interstratified (mixed mineralogy). The soil textures in these mapping units (MUs) are sandy clay loam (SCL), loam sand (LS) and sandy loam (SL) in the Ap horizons of pedons I, 2 and 3 respectively. The subsurface horizons are Silt Loam, SCL and LS. The silt clay ratio (SCR) indicated that the soils are relatively young soils with reserved weatherable minerals, mean SCR were 1.40, 1.50 and 4.00 in pedons 1, 2 and 3 respectively. The acidity decreased as the profile depth increased and it was moderately acidic soil with pH(KCl) ranged from 5.92- 4.75 for pedons. The delta pH (\(\Delta\)pH) of the soils showed all negative values; this indicated that the soil colloids contained appreciable silicate clay minerals with relatively constant surface charge while C/N ratios indicated advanced stage of organic matter decomposition. Percentage Al saturation to the TEA stood at 15%, 19% and 9% for pedons I, 2 and 3 respectively, The exchangeable Ca constitutes above 70 % of the total exchangeable bases (TEB). The percentage base saturation (%BS), was largely dominated by exchangeable cations in moderately to very high rating and their mean values are 80%, 77% and 74% for pedons I, 2 and 3 respectively. The arrays of minerals are at different stages of weathering- quartz and phlogopite at moderate stage of weathering, microcline at minimal stage of weathering while kaolinite and gibbsite are at intense weathering stages. These minimally and moderately weathered soils are generally considered to be of good fertility status. The soils were classified as Alfisols/Entisols mix.

Estimating soil thermal diffusivity at different water contents from easily available data on soil texture, bulk density, and organic carbon content

Growth performance of exotic and indigenous tree species in saline soils in Turkana, Kenya

Invited article: The impacts of non‐native species: a review of the British Ornithologists’ Union's Autumn 2008 Scientific Meeting

Incubation experiment was conducted on four soil types in Nigeria using cattle dung (CD) at the rate -1 -1 of 2.5g/kg soil ( 5 t ha ), Urea fertilizer at the rate of 0.1g/kg soil ( 200 kg ha ) and cattle dung -1 (2.5g/kg soil) combined with Urea 0.05g/kg soil (100 kg ha ) as treatments. The objective of the experiment was to compare the rate of OC, NH 4 – N, NO3 – N and available P release on soils selected from different agro ecological zones of Nigeria. Ten soil samples were collected and bulked from each of the sandy clay, sandy loam, sandy clay loam and loamy sand soils from three different locations within each soil type. The soils were arranged on completely randomized design in laboratory for 60 days. All the treatments reacted differently in each of the soil type in relation to OC, total N, NH4 – N, NO3 – N and available P. In sandy clay and sandy loam soils, all the treatments significantly increased (p < 0.05) OC, total N, NH4 – N, NO3 – N and available P except OC in sandy loam compared with control. In sandy clay loam and loamy sand soils, all the treatments significantly increased (p< 0.05) NH4 – N, NO3 – N and available P. Among all the treatments, CD had the highest OC in all the soil textural classes,, urea had the highest NH4-N and NO3-N while CD + urea had the highest available P (except sandy clay). Cow dung had the highest P in sandy clay. Sand loam and sandy clay loam had highest total N but urea recorded highest value of N in sandy clay while urea+CD mineralized equal amount of total N

O conhecimento do comportamento de herbicidas no ambiente, sobretudo no solo, permite a predição de possíveis impactos do seu uso em sistemas agrícolas. Com o intuito de avaliar a sorção do herbicida imazapyr no solo, foi realizado um experimento, utilizando sorgo (Sorghum bicolor) como planta bioindicadora. A sorção do imazapyr foi avaliada em areia lavada e em três solos, com as seguintes texturas: muito argilosa, franco-argilo-arenosa e areia-franca, provenientes, respectivamente, das cidades de Sete Lagoas, João Pinheiro e Rio Casca, em Minas Gerais. Foram determinados: o valor de I50 (dose que inibiu 50% no acúmulo de massa seca da planta-teste) e a relação de sorção [RS = (I50 solo -I 50 areia)/I50 areia]. Os valores de I50 observados foram: 29,41; 10,20 e 7,33 mg kg-1, e a relação de sorção (RS): 9,77; 2,73 e 1,68, respectivamente para os solos muito argiloso, franco-argilo-arenoso e areia franca. O herbicida imazapyr apresentou a seguinte ordem de sorção nos substratos: muito argiloso &gt; franco-argilo-arenoso &gt; areia-franca &gt; areia lavada. Em solos arenosos e com baixos teores de matéria orgânica, a baixa sorção do imazapyr predispõe o produto à lixiviação no perfil do solo, podendo contaminar mananciais de águas subterrâneas.

Soil detachment is the initial phase of soil erosion and is of great significance to study in seasonal freeze-thaw regions. In order to elucidate the effects mechanism of freeze-thaw cycles on soil detachment capacity of different soils, a sandy loam, a silt loam, and a clay loam were subjected to 0, 1, 5, 10, 15, and 20 freeze-thaw cycles before they were scoured. The results revealed that with increased freeze-thaw cycles, soil bulk density and water-stable aggregates content decreased after the first few times and then kept nearly stable after about 10 cycles, especially for sandy loam. The shear strength of all soils gradually decreased as freeze-thaw cycles increased, except the values of clay loam increased subsequent to the 5th and 15th cycles. After the 20th cycle, the degree of decline of silt loam was the greatest (77.72%), followed by sandy loam (63.18%) and clay loam (39.77%). The soil organic matter of clay loam was much greater than silt loam and sandy loam and all significantly increased after freeze-thaw. Soil detachment capacity of silt loam and sandy loam was positively correlated with freeze-thaw cycle, which was contrary to findings for clay loam. The values of clay loam increased at first and then decreased during the cycles, reaching minimum values at about the 15–20th cycle. After the 20th cycle, the values of sandy loam and silt loam significantly increased 1.62 and 4.74 times over unfrozen, respectively, which was greater than clay loam (0.53 times). A nonlinear regression analysis indicated that the soil detachment capacity of silt loam could be estimated well by soil properties (R2 = 0.87, p &lt; 0.05). This study can provide references for the study of the soil erosion mechanism in seasonal freeze-thaw regions.

Sodic soils of sandy loam, silt loam and clay loam textures having exchangeable sodium percentage (ESP) classes of 20, 40, 60 and 80 were reclaimed with 0, 10, 20, 30 and 40 % solutions of distillery effluent (DE) and gypsum in columns. Soil texture, types of amendment and initial ESP had a larger impact on chemical properties, aggregate stability and size distribution. With increase in concentration of DE, a significant reduction in ESP, pH and insignificant increase in electrical conductivity (EC) of soil was observed for all three textures. Organic carbon (OC) content was also increased significantly in soils amended with DE. Size distribution of water-stable aggregates (WSA) of soils reclaimed using 40 % solution of DE and gypsum were found at par. Depending upon initial ESP and type of amendments used, mean weight diameter (MWD) of WSA varied from 0.51 to 1.14, 0.61 to 1.37 and 0.54 to 1.63 mm for sandy loam, silt loam and clay loam soils respectively. The percentage of water-stable macro-aggregates (WSMA) (>2 mm diameter) ranged from 2.2 to 18.2 in sandy loam, from 2.2 to 19.5 in silt loam and from 4.6 to 28.5 in clay loam soils. Combined as well as individual effects of initial ESP, EC, pH, and OC were found highly significant on WSMA and MWD of WSA in distillery effluent amended soils.

The combined effects of slope gradient, rainfall intensity, and nitrogen fertilizer source on infiltration, runoff, soil loss, and nitrogen (N) leaching in agricultural areas are not thoroughly understood, despite their critical importance in sustainable agriculture. Previous studies have focused on these factors individually, leaving a significant gap in knowledge regarding their synergistic impact. Investigating the interplay between slope gradients, rainfall intensities, and N fertilizer sources is vital to developing effective soil and water conservation strategies and implementing sustainable agricultural practices. This study is comprised of two experiments. Experiment 1 was designed as a 3 × 2 × 3 factorial arrangement, incorporating three levels of rainfall intensity (RI) (45, 70, and 100 mm/h), two slope gradients (5 and 8°), and three soil types (sandy loam, silt loam, and clay loam), aimed at assessing runoff, infiltration, and soil loss. Experiment 2, laid out as 3 × 2 × 3 × 3 factorial, expanded on this, adding N fertilizer source (urea, CaCN2, and limestone ammonium nitrate (LAN) at 130 kg/ha N) and assessing N leaching alongside the previous metrics. Both experiments used a rotating disc rainfall simulator and were replicated four times. Results revealed that steeper slopes (8°) led to increased runoff and soil loss, impeding infiltration, while gentler slopes (5°) facilitated greater infiltration and minimized soil loss. Rainfall intensity played a significant role, with 70 mm/h/5° combinations promoting higher infiltration rates (48.14 mm/h) and 100 mm/h/8° resulting in lower rates (37.07 mm/h for sandy loam and silt loam, 26.09 mm/h for clay loam). Nitrogen leaching varied based on N source; urea at 130 kg/ha N led to higher losses (7.2% in sandy loam, 6.9% in silt loam, 6.5% in clay loam), followed by LAN (6.9% in sandy loam, 6.7% in silt loam, 6.3% in clay loam) while CaCN2 at the same rate resulted in lower N losses (6.4% in sandy soil, 4.4% in silt loam, 4.2% in clay soil). This research highlights the critical need to consider both slope gradient and rainfall intensity in conjunction with appropriate nitrogen fertilizer sources when developing strategies to mitigate soil erosion and nutrient loss in agricultural settings.