Short-term effect of cultivation and crop rotation systems on soil quality indicators in a coastal newly reclaimed farming area

Purpose

Soil quality (SQ), a measure of the sustainability of land use and soil management practices, can be assessed by indicators including soil physical, chemical, and biological properties. Our primary objectives were to investigate the influence of consecutive cultivation and different crop rotation systems on individual SQ indicators and to examine the impact of rotation systems on SQ using soil quality index (SQI) model.

Materials and methods

A site-specific selection of 17 potential SQ indicators representing soil chemical and physical attributes (0–10 cm) and groundwater features on 60 sampling locations and 10 representative soil profiles was chosen in a typical coastal newly reclaimed farmland of north Jiangsu Province, China. Using ANOVA analysis, the crop rotation effect was analyzed by comparing SQ indicators between rice/rape rotation soil and cotton/barley rotation soil. An overall SQI was calculated to examine whether plant biomass indices exactly responded to the SQI value.

Results and discussion

Results indicated that cultivation had significant effect on some soil profile characteristics, including SOM, SOCD, AP, CEC, AK, EC_e, and I _f. Crop rotation systems also had significant influence on some SQ indicators. Compared with cotton/barley rotation soil, rice/rape rotation soil was characterized by higher organic matter, undifferentiated nutrient storage and salinity/alkalinity, lower water accommodation and infiltration, and adverse groundwater conditions. Cotton/barley rotation had higher SQI values over rice/rape rotation (0.523 vs. 0.422). SQ indicators of SAR_e, EC_e, and WT_g contributed the most to the overall SQI value for each rotation system. Plant biomass indices significantly correlated with the SQI values for both rotation systems, suggesting that the SQI values essentially reflected the status of SQ.

Conclusions

Such results allowed us to conclude that cotton/barley rotation system contributed more to the improvement of SQ than rice/rape rotation system in coastal farming area. Also, we suggested SOCD, AK, ρ _b, WT_g, and EC_g as the minimum data set for SQ assessment, as they had potential in discriminating the effect of rotation systems on SQ between the rotation systems used here.     

Long‐term effects of fertilizer and manure applications on soil quality and yields in a sub‐humid tropical rice‐rice system

Widespread yield stagnation and productivity declines in the rice–rice cropping system have been reported and many of the associated issues are related to soil quality. A long‐term experimental study was initiated in 1969 to assess the impact of continuous cultivation of rice as a single crop grown in wet as well as dry seasons using varying levels of chemical fertilizer and manure applications on soil quality indicators (physical, chemical and biological), a sustainable yield index (SYI) and a soil quality index (SQI). The treatments comprised chemical fertilizers and farmyard manure (FYM) either alone or in combination viz. control, N, NP, NK, NPK, FYM, N+FYM, NP+FYM, NK+FYM and NPK+FYM, laid out in a randomized complete block design with three replications. Soil samples were collected after the wet season rice harvest in 2010 and were analysed for physical, chemical and biological indicators of soil quality. A SYI based on long‐term yield data and SQI using principal component analysis (PCA) and nonlinear scoring functions were calculated. Application of NPK fertilizers in combination with FYM significantly increased the average grain yield of rice in both wet and dry seasons and enhanced the sustainability of the system compared to the control and plots in receipt of fertilizers. The SYI for the control was higher in the wet season than in the dry one, whereas the reverse was true for NPK+FYM treatment. The value of the dimensionless SQI varied from 1.46 in the control plot to 3.78 in the NPK+FYM one. A greater SYI and SQI in the NPK+FYM treatment demonstrated the importance of using a chemical fertilizer in combination with FYM. For the six soil quality indicators selected as a minimum data set (MDS), the contribution of DTPA‐Zn, available‐N and soil organic carbon to the SQI was substantial ranging from 59.4 to 85.7 per cent in NPK+FYM and control plots, respectively. Thus, these soil parameters could be used to monitor soil quality in a subhumid tropical rice–rice system.     

Cumulative effects of a 17‐year chemical fertilization on the soil quality of cropping system in the Loess Hilly Region,China

Soil‐quality assessment provides a tool for evaluating the sustainability of alternative soil‐management practices. Understanding the effects of the long‐term use of chemical fertilizers on soil quality is essential for sustaining soil productivity. The cumulative effect of a 17‐y‐old chemical‐fertilizer application on integrated soil quality was investigated in the surface (0–15 cm) and subsurface (15–30 cm) soils of a soy–broomcorn–millet cropping system with an experiment design of two factors with three levels for each factor. The treatments were N0P0, N0P1, N0P2, N1P0, N1P1 (local farmer' fertilization strategy), N1P2, N2P0, N2P1, N2P2, and a control NF. The objectives were to describe and quantify the effect of continuous applications of chemical fertilizer through soil‐quality index (SQI) and attempt to offer an efficient and appropriate nutrient‐supply strategy for the local region. Following 17 y of chemical fertilization, the SQI increased markedly in the studied soil layers, and soil chemical indicators changed more significantly than physical properties. The soil‐quality indicators in the surface soil layer were more variable and sensitive to fertilizer application than the subsurface layer. The indicators that sensitively responded to long‐term fertilization could be classified into three types: soil‐fertility indicators (soil organic matter [SOM], total P, and available N), soil‐texture indicators (clay, silt), and soil‐structure indicators (bulk density, mean weight diameter [MWD]). The simplified indicators (SOM, sand, available N, bulk density, and total P in the surface soil and SOM, MWD, and silt content in the subsurface soil) preferably reflected the status of the integrated soil quality as influenced by continuous fertilization. Among the fertilized treatments, the combined‐fertilizer treatments maintained a higher SQI than the single‐fertilizer treatments in the surface and subsurface soils. The N1P2 treatment maintained the highest SQI in both soil layers, followed by N1P1 treatment. However, for the slope cropland, given the relative costs, soil resource, and environmental protection, the traditional treatment of N1P1 may be the optimal fertilizer treatment in the local region.     

Long‐term effects of organic manure and manufactured fertilizer additions on soil quality and sustainable productivity of finger millet under a finger millet–groundnut cropping system in southern India

In a 20‐yr‐old long‐term experiment, the impact of continuous application of organic manures and inorganic fertilizers on soil quality and the sustainability of finger millet production was conducted on two cropping systems: finger millet and finger millet–groundnut on an Alfisol of semi‐arid southern India. The study was conducted from 1992 to 2011 at the All India Coordinated Research Project for Dryland Agriculture, UAS, Bangalore, using a randomized block design. The treatments comprised of T₁: control [no fertilizer and no farmyard manure (FYM) applied], T₂: FYM 10 t/ha, T₃: FYM 10 t/ha + 50% of recommended NPK (50:50:25 kg/ha), T₄: FYM 10 t/ha + 100% of recommended NPK and T₅: 100% recommended NPK. Comparison of long‐term yield data between treatments was used to calculate a ‘sustainability yield index’ (SYI), which was greatest for T₄ (FYM 10 t/ha + 100% of recommended NPK), in both rotational (0.68) and monocropping (0.63) situations. Soil quality indices were determined using principal component analysis linear scoring functions. The key indicators which contributed to the soil quality index (SQI) under rotation were organic C; potentially available N; extractable P, K and S; exchangeable Ca and Mg; dehydrogenase activity and microbial biomass C and N. The largest SQI (7.29) was observed in T₄ (FYM 10 t/ha + 100% NPK), and the smallest (3.70) SQI was for the control. Application of 10 t/ha FYM together with NPK (50:50:25 kg/ha) sustained a mean yield of 3884 kg/ha.     

Characterization of field‐scale dryland salinity with depth by quasi‐3d inversion of DUALEM‐1 data

To understand the limitations of saline soil and determine best management practices, simple methods need to be developed to determine the salinity distribution in a soil profile and map this variation across the landscape. Using a field study in southwestern Australia, we describe a method to map this distribution in three dimensions using a DUALEM‐1 instrument and the EM4Soil inversion software. We identified suitable parameters to invert the apparent electrical conductivity (EC_a – mS/m) data acquired with a DUALEM‐1, by comparing the estimates of true electrical conductivity (σ – mS/m) derived from electromagnetic conductivity images (EMCI) to values of soil electrical conductivity of a soil‐paste extract (EC_e) which exhibited large ranges at 0–0.25 (32.4 dS/m), 0.25–0.50 (18.6 dS/m) and 0.50–0.75 m (17.6 dS/m). We developed EMCI using EM4Soil and the quasi‐3d (q‐3d), cumulative function (CF) forward modelling and S2 inversion algorithm with a damping factor (λ) of 0.07. Using a cross‐validation approach, where we removed one in 15 of the calibration locations and predicted EC_e, the prediction was shown to have high accuracy (RMSE = 2.24 dS/m), small bias (ME = ?0.03 dS/m) and large Lin's concordance (0.94). The results were similar to those from linear regression models between EC_a and EC_e for each depth of interest but were slightly less accurate (2.26 dS/m). We conclude that the q‐3d inversion was more efficient and allowed for estimates of EC_e to be made at any depth. The method can be applied elsewhere to map soil salinity in three dimensions.     

中国东北农田土壤质量评价的最小数据集选择

Soil quality assessment provides a tool for agriculture managers and policy makers to gain a better understanding of how various agricultural systems afect soil resources.Soil quality of Hailun County,a typical soybean (Glycine max L.Merill) growing area located in Northeast China,was evaluated using soil quality index(SQI)methods.Each SQI was computed using a minimum data set(MDS) selected using principal components analysis(PCA)as a data reduction technique.Eight MDS indicators were selected from 20 physical and chemical soil measurements.The MDS accounted for 74.9% of the total variance in the total data set(TDS).The SQI values for 88 soil samples were evaluated with linear scoring techniques and various weight methods.The results showed that SQI values correlated well with soybean yield (r=0.658**) when indicators in MDS were weighted by the regression coefcient computed for each yield and index.Stepwise regression between yield and principal components (PCs) indicated that available boron(AvB),available phosphorus (AvP),available potassium (AvK),available iron (AvFe) and texture were the main factors limiting soybean yield.The method used to select an MDS could not only appropriately assess soil quality but also be used as a powerful tool for soil nutrient diagnosis at the regional level.     

World's Oldest Cotton Experiment: Relationships between Soil Chemical and Physical Properties and Apparent Electrical Conductivity

Abstract

Measuring and mapping apparent soil electrical conductivity (EC_a) is a potentially useful tool for delineating soil variability. The “Old Rotation,” the world's oldest continuous cotton (Gossypium hirsutum L.) experiment (ca. 1896), provides a valuable resource for evaluating soil spatial variability. The objectives of this study were to determine the relationship between soil chemical and physical properties and EC_a in the Old Rotation, to determine spatial differences in these properties, and to relate differences in these properties to long‐term management effects. Soils at the site classified as fine, kaolinitic, thermic Typic Kanhapludults. Soil EC_a was measured at 0–30‐ and 0–90‐cm depths (EC_a‐30 and EC_a‐90) using a Veris^® 3100 direct contact sensor with georeferencing. Soils were grid sampled (288 points) at close intervals (1.5×3.0 m) for chemical properties and grid sampled (65 cells, 7.5×6.9 m) for soil texture. Soil organic carbon (SOC) and total nitrogen (N), extractable phosphorus (P), potassium (K), calcium (Ca), pH, buffer pH, and estimated cation exchange capacity (CEC_est) were measured at two depths (0–5‐ and 5–15‐cm). Soil EC_a was highly spatially correlated. The EC_a‐30 was more highly correlated with clay content (r=0.58, P≤0.01) and P(r=0.43, P≤0.01) than other soil properties. Total nitrogen and SOC had little or no relationship with EC_a‐30. Cropping systems affected chemical properties in the Old Rotation, indicating crop rotation and cover crops are beneficial for soil productivity. The relatively poor relationship between soil chemical parameters and EC_a suggest that mapping plant nutrients and SOC using EC_a is problematic because of strong dependence on clay content.     

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.     

Potassium‐fertilizer management in winter oilseed‐rape production in China

Optimal potassium (K) fertilization is beneficial for oilseed‐rape (Brassica napus L.) yield and quality. However, the discrepancy between the high K demand of winter oilseed rape and low soil fertility and insufficient potassium input has limited the sustainable development of oilseed‐rape production. A series of on‐farm experiments in the key winter oilseed‐rape domains of China was conducted from 2004 to 2010 to evaluate K‐fertilizer management for winter oilseed rape. Currently, the average NH₄OAc‐extractable K content in the 0–20 cm soil layer is 89.1 mg kg^–1 indicative of “slight deficiency”. In addition, farmers in China usually fail to use sufficient K fertilizer in oilseed‐rape production, the average mineral‐potassium‐fertilizer input in 2010 being only 35 kg K ha^–1, far lower than the recommended rate of potassium for winter oilseed rape. Adequate potassium fertilization significantly raises seed yield. The average yield‐increase rate for the major production regions due to K‐fertilizer application was 18.5%, and the average K fertilizer–use efficiency 36.1%. Based on the negative correlation between yield response to potassium fertilization and available soil K content, a soil‐K‐test index was established for winter oilseed rape with a threshold value for NH₄OAc‐extractable soil K of 135 mg kg^–1. When available soil K‐content is below this threshold value, more K fertilizer should be applied to achieve high seed yield and to increase soil fertility. The major challenge for K‐fertilizer management in winter oilseed‐rape production in China will be to guide farmers in the different regions in making reasonable use of K fertilizer through soil K‐testing technology in order to maintain both seed yield and soil fertility.     

Assessment of Horizantal and Vertical Variabilities of Soil Quality using Multivariate Statistics and Geostatistical Methods

The aim of this study is to examine the horizantal and vertical spatial changes of soil quality (SQ) in rice-cultivated soils located on the Bafra Deltaic Plain—one of the most important alluvial deltaic plains and production centers of Turkey. The study examines these spacial changes by calculating the soil quality index (SQI) for soils 0–30 cm and 30–60 cm deep. For SQI calculations, seventeen potential physicochemical SQ indicators of eighty-three soil samples were assessed. Quality indicators to be used in these calculations were selected by considering the clay content, correlation relationship, and principal components analysis (PCA) of potential quality indicators. Clay, silt, sand, electrical conductivity (EC), exchangeable calcium (Ca_exc), and exchangeable magnesium (Mg_exc) were selected as quality indicators, and silt was found to be the most important quality indicator for both soil depths. The SQ of researched soils changed from low to high for both soil depths.     

Changes in N leaching and crop production as a result of measures to reduce N losses to water in a 6‐yr crop rotation

The effects of various measures introduced to increase nitrogen (N)‐use efficiency and reduce N losses to water in a 6‐yr crop rotation (winter wheat, spring barley, green manure, winter wheat, spring barley, spring oilseed rape) were examined with respect to N leaching, soil mineral N (SMN) accumulation and grain yield. An N‐use efficient system (NUE) with delayed tillage until late autumn and spring, direct drilling of winter wheat, earlier sowing of winter and spring crops and use of a catch crop in winter wheat was compared with a conventional system (CON) in a field experiment with six separately tile‐drained plots in south‐western Sweden during the period 1999–2011 (two crop rotation cycles). Total leaching of NO₃‐N from the NUE system was significantly 46 and 33% lower than in the CON system during the first and second crop rotation cycle, respectively, with the most pronounced differences apparently related to management strategies for winter wheat. Differences in NO₃‐N leaching largely reflected differences in SMN during autumn and winter. There was a tendency for lower yields in the NUE system, probably due to problems with couch grass. Overall, the measures for conserving N, when frequently used within a crop rotation, effectively reduced NO₃ concentrations in drainage water and NO₃‐N leaching losses, without severely affecting yield.     

Soil Quality Indicators Response to Land Use and Soil Management Systems in Northern Ethiopia's Catchment

Assessment of soil quality (SQ) indicators that detect soil degradation in different land use and soil management systems (LUSMS) is desirable to achieve sustainable management strategies. The LUSMS identified for evaluation included natural forest (LS1), plantation of protected area (LS2), grazed land (LS3), teff (Eragrostis tef)‐faba bean (Vicia faba) rotation (LS4), teff‐wheat (Triticum vulgare)/barley (Hordeum vulgare) rotation (LS5), teff mono‐cropping (LS6), maize (Zea mays) mono‐cropping (LS7), and uncultivated marginal land (LS8). The SQ indicators were significantly influenced (p ≤ 0·05) by the LUSMS. The first four principal components with eigenvalue > 1 explain about 88% of the SQ variability across the LUSMS. The final principal component chosen indicators that mainly influence SQ variability were organic carbon, total nitrogen, cation exchange capacity, total phosphorus, silt, bulk density, and iron. In this study, a higher SQ was found in LS1 followed by LS2, whereas a seriously degraded SQ was observed in LS8 followed by LS6. Copyright © 2013 John Wiley & Sons, Ltd.     

Short-term changes in chemical and microbial characteristics of paddy soil in response to consecutive addition of organic ameliorants in a rice–rice–vegetable rotation system

With regard of the problems of soil acidification and soil degradation caused by high intensive planting in south China, a 2-year pot experiment consisting of six harvests under a rice–rice–vegetable rotation cropping system was conducted to assess the effects of NPK+ rice straw (RS) and combined application of RS with peanut bran, biochar, and organic fertilizer on soil chemical and microbial characteristics in paddy soil. The control treatment received chemical fertilizer alone. Results showed that RS and the combination of RS with organic ameliorants, especially NPK+ rice straw + biochar (RSBC) treatment led to the greatest improvement of soil pH, soil organic carbon, microbial biomass carbon, and total nitrogen (TN) content, and urease (UE), acid phosphatase (ACP) and catalase (CAT) activities concurrently without yield sacrificing, which inferred that RSBC treatment could be an effective measure to alleviate soil acidification, boost carbon sequestration and nutrients content as well as soil enzyme activities in rice-rice-vegetable rotation system. Besides, Pearson’s correlation analysis showed that soil mineral nitrogen (N_min) content was negatively related to pH, and the available potassium (AK) content was positively related to UE and CAT activity but negatively related to ACP activity. Canonical correspondence analysis demonstrated the N_min and AK explained 27.2% and 13.7% of the variation in microbial species, respectively. Therefore, it is believed that soil N_min and AK content could be the primary factors of soil microbial properties under the rice-rice-vegetable rotation system.     

Conservation Tillage,Rotations, and Cover Crop Affecting Soil Quality in the Tennessee Valley: Particulate Organic Matter,Organic Matter,and Microbial Biomass

Abstract

The impact of conservation tillage, crop rotation, and cover cropping on soil‐quality indicators was evaluated in a long‐term experiment for cotton. Compared to conventional‐tillage cotton, other treatments had 3.4 to 7.7 Mg ha^?1 more carbon (C) over all soil depths. The particulate organic matter C (POMc) accounts for 29 to 48 and 16 to 22% of soil organic C (SOC) for the 0‐ to 3‐and 3‐ to 6‐cm depths, respectively. Tillage had a strongth influence on POMc within the 0‐ to 3‐cm depth, but cropping intensity and cover crop did not affect POMc. A large stratification for microbial biomass was observed varing from 221 to 434 and 63 to 110 mg kg^?1 within depth of 0–3 and 12–24 cm respectively. The microbial biomass is a more sensitive indicator (compared to SOC) of management impacts, showing clear effect of tillage, rotation, and cropping intensity. The no‐tillage cotton double‐cropped wheat/soybean system that combined high cropping intensity and crop rotation provided the best soil quality.     

Improving dryland cropping system nitrogen balance with no‐tillage and nitrogen fertilization

Studies on N balance due to N inputs and outputs and soil N retention to measure cropping system performance and environmental sustainability are limited due to the complexity of measurements of some parameters. We measured N balance based on N inputs and outputs and soil N retention under dryland agroecosystem affected by cropping system and N fertilization from 2006 to 2011 in the northern Great Plains, USA. Cropping systems were conventional tillage barley (Hordeum vulgaris L.)–fallow (CTB‐F), no‐tillage barley–fallow (NTB‐F), no‐tillage barley–pea (Pisum sativum L.) (NTB‐P), and no‐tillage continuous barley (NTCB). In these cropping systems, N was applied to barley at four rates (0, 40, 80, and 120 kg N ha^?1), but not to pea and fallow. Total N input due to N fertilization, pea N fixation, soil N mineralization, atmospheric N deposition, nonsymbiotic N fixation, and crop seed N and total N output due to grain N removal, denitrification, volatilization, N leaching, gaseous N (NO_x) emissions, surface runoff, and plant senescence were 28–37% greater with NTB‐P and NTCB than CTB‐F and NTB‐F. Total N input and output also increased with increased N rate. Nitrogen accumulation rate at the 0–120 cm soil depth ranged from –32 kg N ha^?1 y^?1 for CTB‐F to 40 kg N ha^?1 y^?1 for NTB‐P and from –22 kg N ha^?1 y^?1 for N rates of 0 kg N ha^?1 to 45 kg N ha^?1 y^?1 for 120 kg N ha^?1. Nitrogen balance ranged from 1 kg N ha^?1 y^?1 for NTB‐P to 74 kg N ha^?1 y^?1 for CTB‐F. Because of increased grain N removal but reduced N loss to the environment and N fertilizer requirement as well as efficient N cycling, NTB‐P with 40 kg N ha^?1 may enhance agronomic performance and environmental sustainability while reducing N inputs compared to other management practices.     

Soil quality indices for evaluation of long‐term land use and soil management practices in semi‐arid sub‐tropical India

Land use changes and soil management can potentially alter soil quality. A study was conducted to assess the long‐term (>20 years) effects of perennial trees (PT), vegetable crops (VC), rice–wheat (RW) system, sewage‐irrigated fields (SF), maize–wheat (MW) system and uncultivated soils (US) on soil quality. Soil physical quality parameters were significantly affected only in the SF system when compared with the US soil, particularly for bulk density (BD 1·51 Mg m⁻³ in SF vs. 1·34 in US). Among chemical parameters, electrical conductivity was high in SF, and soil nutrients (N, P, K, S, Zn, Fe, Cu and Mn) were well above the critical limits of deficiency in all the systems. Soil parameters were integrated into soil quality indices (SQIs) by unscreened transformation and principal component analysis (PCA). SQI observed under each system were compared with the US to assess the degree of degradation. Mean SQI differences showed that PT (+16·02 per cent), VC (+4·80 per cent), RW (+10·04 per cent), and MW (+11·30 per cent) are aggrading, whereas SF (−2·06 per cent) is degrading with respect to the reference soil (US). Adoption of MW system proved to be better than traditional RW; and in general agricultural crops have a significant advantage than VC, in terms of maintaining soil quality. Sewage irrigation is not a sustainable practice and long‐term use may degrade the soil. Among the SQIs, PCA with nonlinear scoring function (NLSF) based SQI was effective in judging land degradation due to soil quality changes as affected by long‐term land use and soil management practices. Copyright © 2008 John Wiley & Sons, Ltd.     

Cropping systems and bed width effects on runoff,erosion and soil properties in a rainfed Vertisol

The effects of two bed widths (1 and 2 m) and four rainfed cotton‐based cropping systems on soil properties, runoff and erosion were evaluated in a Vertisol (1 per cent slope; 21 g per 100 g sand, 12 g per 100 g silt, 67 g per 100 g clay) in subtropical central Queensland, Australia. The cropping systems were: early cotton (Gossypium hirsutum L.) sown between August and October; wheat (Triticum aestivum L.) sown in May, sprayed out and followed by early cotton; wheat allowed to mature, harvested and followed by late cotton sown between October and December; and grain sorghum (Sorghum bicolor (L.) Moench.) followed by cotton. Land preparation was by minimum tillage and traffic was restricted to the furrows between the beds. Rainfall runoff and soil erosion were monitored with water‐height recorders, flumes and troughs. Soil structure was evaluated as air‐filled porosity of oven‐dried soil in the 0–0.15, 0.15–0.30, 0.30–0.45 and 0.45–0.60 m depths. Soil chemical properties measured in the 0–0.15 m depth were organic carbon, pH (in 0.01 M CaCl₂), electrical conductivity (EC_1:5) of a 1 : 5 soil : water suspension and exchangeable Ca, Mg, K and Na. In comparison with 1 m beds, 2 m beds resulted in lower runoff and soil erosion, lower exchangeable Na, exchangeable sodium percentage and higher EC_1:5/exchangeable Na, higher rate of soil organic matter decrease and better soil structure in the 0–0.15 m depth. Runoff and erosion were reduced, and cotton lint yields increased either by cropping systems sown early to intercept most of the seasonal rainfall or by those which produced a high level of ground cover. Soil physical and chemical properties were best, and runoff and erosion lowest with 2 m beds and cropping systems producing a high level of ground cover. Copyright © 2002 John Wiley & Sons, Ltd.     

Investigating soil physical properties and yield response in a grassland field using a dual‐sensor penetrometer and EM38

Precision‐farming applications are mainly based on site‐specific information of soil properties at the field scale. For this purpose, a number of novel sensor techniques have been developed but not intensively tested under different field conditions. This study presents a combined application of a self‐developed dual‐sensor vertical penetrometer (DVP) for measuring volumetric soil water content (VSWC) and cone index (CI), and an EM38 for soil apparent electrical conductivity (EC_a) in a pasture (1.4 ha). To verify the feasibility of the DVP for interpreting the depth‐specific information in the field, not only the soil physical properties and their geographical coordinates were measured, but also geo‐referenced yield data were collected. We found that the yield pattern was quite similar to the soil water‐content pattern of each layer (layer‐1: 5–15 cm; layer‐2: 15–25 cm, layer‐3: 25–35 cm) and EC_a pattern. Using the map‐based comparisons in conjunction with the statistical analyses, the effect of each measured soil physical property (VSWC, CI, and EC_a) on the yield was investigated. The regression between the yield and VSWC at each layer fitted a quadratic equation (R² = 0.515 at 5–15 cm; R² = 0.623, at 15–25 cm; R² = 0.406 at 25–35 cm). The negative correlation between yield and CI at each layer fitted a linear model with R² ≥ 0.510.     

Effects of different cropping systems on soil water properties of a Boralf soil

Abstract

A long‐term field experiment utilizing five different cropping systems was established on a Boralf soil in 1968 in the Peace River region of Alberta, Canada. The cropping systems consisted of: continuous barley (CB), barley/forage (Bf) (3 y of barley followed by 3 y of forage), forage/barley (Fb) (3 y of forage followed by 3 y of barley), continuous grass (CG) as bromegrass and continuous legume (CL) as red clover. The saturated conductivity (K_sat) was improved by growing forage crops as the CG and CL cropping systems had a higher K_sat (1.20×10^‐2 and 1.57×10^‐2 cm h^‐1) than the Fb, Bf, and CB cropping systems (4.41×10^‐3, 5.01×10^‐3 and 4.50×10^‐4 cm hr^‐1, respectively) for the 15–30 cm depth. At the 30–45 cm depth the CL cropping system K_sat was a hundred fold greater, at 10^‐2 compared to 10^‐4 cm hr^‐1. The infiltration and the depth of accumulated water over time also reflected forage production cropping practices as the CG and CL cropping systems had the highest infiltration rates at 30 min of 9.7 and 9.4 mm hr^‐1 while the Fb, Bf, and CB cropping systems had infiltration rates of 4.8, 7.1 and 8.3 mm hr^‐1. The ratio of the infiltration rate at the beginning versus the end of the infiltration period (30 to 480 min) of 4.0, 5.6, 6.4, 6.4, and 7.0 although not significant indicated decreasing structural stability in the order of: CG > CL > Bf > Fb > CB cropping systems, respectively. It was observed that differences in soil water properties due to cropping history were reflected.     

Effects of short‐rotation Eucalyptus plantations on soil quality attributes in highly acidic soils of the central highlands of Ethiopia

In recent decades, conversion of agricultural land to short‐rotation (5–10 years) Eucalyptus plantations has become a common practice in the highlands of Ethiopia. Yet, we have a poor understanding of the effect of these land conversions on soil quality attributes under acidic soil conditions. Previous studies along the same line but based merely on physico‐chemical properties of soils were inconsistent and contradictory. We compared soil physical, chemical and biological properties under 5‐ and 10‐year‐old Eucalyptus plantations with adjacent grassland soils. Results revealed that soil bulk density of adjacent grassland was significantly smaller than in the two Eucalyptus plantations. Although land‐use change from grassland to short‐rotation Eucalyptus did not affect soil texture significantly, values of soil pH, organic carbon, total nitrogen, calcium and cation exchange capacity (CEC) values in adjacent grassland were greater at both 0–10 cm and 10–20 cm depths compared with 5‐ and 10‐year‐old Eucalyptus plantations. Available phosphorus, exchangeable potassium and magnesium were not significantly affected under the three land‐use systems. Generally, no differences were observed in available phosphorus, potassium, calcium and magnesium concentrations or in CEC between the two sampling depths (0–10 cm and 10–20 cm). The microbial biomass carbon and microbial biomass nitrogen recorded in 5‐ and 10‐year‐old Eucalyptus plantations were comparable but significantly smaller than in adjacent grasslands. Kinetics parameters calculated using a first‐order equation (C_t = C_o (1?e^?kt)) showed potentially mineralizable carbon (C_o) was significantly larger (P < 0.001) under grassland compared with 5‐ and 10‐year‐old Eucalyptus plantations. Conversion of grassland to 5‐year‐old and 10‐year‐old Eucalyptus reduced the values of C_o by 21 and 43%, respectively. However, soil physical and chemical properties were not adversely affected by age of Eucalyptus over a 5‐year period. It is concluded that Eucalyptus plantations degrade soil ecosystem functioning and environmental sustainability compared with grassland.