Tillage and agricultural sustainability

Agricultural sustainability implies an increasing trend in per capita productivity to meet the present needs without jeopardizing the future potential. Soil tillage, soil surface management to alleviate soil-related constraints to crop production, is a basic and an important input with short- and long-term effects on sustainability. An important effect of soil tillage on sustainability is through its impact on the environment e.g. soil degradation, water quality, emission of greenhouse gases from soil-related processes, etc. The need to attain agricultural sustainability is particularly urgent in several tropical eco-regions and soils of low-carrying capacity in the tropics.

Soil tillage influences atricultural sustainability through its effects on soil processes, soil properties, and crop growth. However, there is no one blueprint of a universally applicable sustainable tillage system. Appropriate tillage systems are soil- and crop-specific and their adaptation is governed by both biophysical and socio-economic factors. In addition to increasing crop yields, tillage methods must also facilitate soil and water conservation, improve root system development, maintain a favorable level of soil organic matter content, and reverse degradative in the soil's life-support processes.

Important components or sub-systems of conservation-effective tillage systems include mulch farming, no-till or reduced tillage systems, use of cover crops and planted fallows, agroforestry, raised beds or ridge-tillage, and soil inversion or deep plowing. The ecological limits for the applicability of these components or sub-systems differ widely. The efforts of a multi-disciplinary team (comprising soil scientists, agricultural engineers, agronomists, economists and social scientists) are needed to develop site-specific tillage methods to achieve both short- and long-term goals of agricultural sustainability.     

Improved management of Vertisols in the semiarid tropics for increased productivity and soil carbon sequestration

Abstract. This study was undertaken to test the hypothesis that an improved system of catchment management in combination with appropriate cropping practices can sustain increased crop production and improve soil quality of Vertisols, compared with prevailing traditional farming practices. Initiated in 1976, the improved system consisted of integrated land management to conserve soil and water, with excess rainwater being removed in a controlled manner. This was combined with improved crop rotation (legume based) and integrated nutrient management. In the traditional system, sorghum or chickpea was grown in the post-rainy season with organic fertilizers, and in the rainy season the field was maintained as a cultivated fallow. The average grain yield of the improved system over 24 years was 4.7 t ha⁻¹ yr⁻¹, nearly a five-fold increase over the traditional system (about 1 t ha⁻¹ yr⁻¹). There was also evidence of increased organic C, total N and P, available N, P and K, microbial biomass C and N in the soil of the improved system. A positive relationship between soil available P and soil organic C suggested that application of P to Vertisols increased carbon sequestration by 7.4 t C ha⁻¹ and, in turn, the productivity of the legume-based system, thus ultimately enhancing soil quality.     

Reduced tillage and increasing cropping intensity in the Great Plains conserves soil C

Concern about soil organic matter losses as a result of cultivation has been voiced consistently since the early part of the 20th century. Scientists working in the US. Great Plains recognized that organic matter losses from an already small pool could have major negative consequences on soil physical properties and N supplying capacity. The advent of reduced- and no-till systems has greatly improved our ability to capture and retain precipitation in the soil during the non-crop periods of the cropping cycle, and has made it possible to reduce fallow frequency and intensify cropping systems. The purpose of this paper is to summarize the effects of reduced tillage and cropping system intensification on C storage in soils using data from experiments in North Dakota, Nebraska, Kansas, Colorado, and Texas. Decades of farming with the wheat (Triticum aestivum L.)–fallow system, the dominant farming system in the Great Plains, have accentuated soil C losses. More intensive cropping systems, made possible by the greater water conservation associated with no-till practices, have produced more grain, produced more crop residue and allowed more of it to remain on the soil surface. Combined with less soil disturbance in reduced- and no-till systems, intensive cropping has increased C storage in the soil. We also conclude that the effects of cropping system intensification on soil C should not be investigated independent of residue C still on the surface. There are many unknowns regarding how rapidly changes in soil C will occur when tillage and cropping systems are changed, but the data summarized in this paper indicate that in the surface 2.5 cm of soil, changes can be detected within 10 years. It is imperative that we continue long-term experiments to evaluate rates of change over an extended period. It is also apparent that we should include residue C, both on the surface of the soil and within the surface 2.5 cm, in our system C budgets if we are to accurately depict residue–soil C system status. The accounting of soil C must be done on a mass basis rather than on a concentration basis.     

Controlled traffic farming—From research to adoption in Australia

Efficient mechanisation is a major factor underlying the high productivity and low cost of most Australian crop production systems. Efficiency has generally been associated with greater work rates, achieved by using equipment of greater power and weight. This trend has continued until very recently, despite a reduction in tillage for weed control.

Scientists have warned of erosion and soil structural degradation caused by tillage and traffic, but tillage, rather than field traffic was seen as the major problem, and reduction of tillage as the solution. Reduced tillage has provided major benefits, but adoption has occurred slowly and sustained zero tillage is still rare, except in controlled traffic farming systems.

The first part of this paper presents research evidence of the direct cost, practical impact and long-term effects of wheel traffic on cropped soil. Direct cost is associated with the energy requirements of disturbing wheeled soil. Practical impact occurs as a result of the lost opportunities and additional operations associated with wheel ruts. Long-term productivity and environmental impact occur because wheel traffic reduces plant available water and increases runoff and erosion.

In controlled traffic all equipment wheels are restricted to compacted permanent traffic lanes, so that soil in the crop beds and traffic lanes can be managed respectively for optimum cropping and optimum trafficability. Controlled traffic farming recognizes the symbiosis between controlled traffic and zero tillage in providing opportunities for more productive and sustainable farming of soil uncompromised by wheel effects.

The beneficial effects of controlled traffic have been demonstrated in widely different soils and mechanisation systems (e.g. Australia and China), and it has been vigorously advocated in both the USA and Europe, but large-scale adoption has been rare. The second part of this paper discusses cropping system response to controlled traffic farming, and the program which led to large-scale adoption in Australia. This happened first in extensive grain production, but adoption has since occurred in many Australian farming systems, supported by the availability of high-precision field guidance systems and a greater range of compatible equipment.

Controlled traffic farming reduces soil degradation and the energy requirements of cropping. It is also more productive, and its practicality and economic viability have been clearly demonstrated in enthusiastic farmer adoption, and the formation of an Australian Controlled Traffic Farming Association.     

Changes in soil microbial properties with no-tillage in Chinese cropping systems

No-tillage (NT) has revolutionized agricultural systems because it has potential benefits including soil conservation and reduced production costs though saving in fuel, equipment, and labor. Soil quality is of great importance in determining the sustainability of land management systems, and soil microbial properties are becoming increasingly used to assess the effect of farming practices on soil quality due to their quick response, high sensitivity, ecological relevance, and capacity to provide information that integrates many environmental factors. In China, research and application of NT have developed quickly since 1970s. Numerous studies have been conducted in this country to evaluate the effect of NT on soil microbial properties. From these studies, it is evident that NT can lead to an increase in soil microbial size or activity or both and a consequent increase in soil microbial biomass in upland cropping systems. However, there are still several issues that remain unaddressed or inadequately specified. Further investigations are needed (1) to determine the effect of NT on soil microbial diversity by using molecular biological techniques in both upland and rice-based cropping systems; (2) to fully understand the changes of soil microbial properties with NT in rice-based cropping systems, especially for double rice cropping systems; and (3) to clarify the relationship between rhizosphere microbial properties and crop growth in NT rice cropping systems.     

Role of Soil Organic Matter in Maintaining Sustainability of Cropping Systems

Soil organic matter (SOM) has long been recognized as an important indicator of soil productivity. The SOM refers to the organic fraction of the soil exclusive of undecayed plant and animal residues. It plays a crucial role in maintaining sustainability of cropping systems by improving soil physical (texture, structure, bulk density, and water-holding capacity), chemical (nutrient availability, cation exchange capacity, reduced aluminum toxicity, and allelopathy), and biological (nitrogen mineralization bacteria, dinitrogen fixation, mycorrhizae fungi, and microbial biomass) properties. The preservation of SOM is crucial to ensure long-term sustainability of agricultural ecosystems. Improvement/preservation of soil organic matter can be achieved by adopting appropriate soil and crop management practices. These practices include conservation tillage, crop rotation, use of organic manures, increasing cropping intensity, use of adequate rate of chemical fertilizers, incorporation of crop residues, liming acidic soils, and keeping land under pasture. Organic matter can adsorb heavy metals in the soils, which reduce toxicity of these metals to plants and reduce their escape to ground water. Similarly, SOM also adsorbs herbicides, which may inhibit contamination of surface and ground water. Furthermore, SOM also functions as a sink to organic carbon and mitigates carbon dioxide (CO₂) gas escape to the environment. Globally, soil organic matter contains about three times as much carbon as found in the world's vegetation. Hence, organic matter plays a critical role in the global carbon balance that is thought to be the major factor affecting global warming. Overall, adequate amounts of soil organic matter maintain soil quality, preserve sustainability of cropping systems, and reduce environmental pollution.     

Conceptual methodologies in agro-environmental systems

When continuous measurement of relevant above- and below-ground environmental factors is made, and the dynamics of crop growth and phenology is followed, it is shown that small-plot agronomic experimentation can provide information vital to the development and testing of simulation models. Such models for crops of maize (Zea mays) and the legume cowpea (Vigna unguiculata), grown as sole crops and in an intercrop system, were used to simulate yield at two separate sites in the main savanna farming zones in Ghana, West Africa. Simulation was carried out for these three cropping systems using 20 years of historical rainfall data for the two sites, investigating the effect on yield of management options which included time of planting, rate of nitrogen fertilizer application, and crop planting density.

The yield results of this series of simulations were then subject to two different types of analysis in order to assist the evaluation of agricultural options for the nation. The first analysis was an economic evaluation based on gross margins, but using the stochastic-dominance technique to rank the profitability of the alternative cropping and management systems.

The second, more general methodology employed was multi-criteria analysis (MCA). This analysis covered economic returns and their variability, the amount and quality of residue returned to the soil, and the aerial cover provided by the crop. Other factors which could affect the sustainability of production in the long term, but which could only be evaluated qualitatively, were also included in the analysis, as allowed in MCA methodology. The MCA was then carried out for three scenarios in which different weightings were given to economic outcomes and to factors which are believed to encourage ecological sustainability. These scenarios allow recognition of different priorities which might be given by traditional subsistence farmers as compared to commercial producers.

Outcomes of this broad analysis of development alternatives provided scientific support for the traditional Ghanaian practice of grain/legume intercropping which is also widespread in the tropics. The suite of methodologies illustrated by the case study appears to be suitable for the evaluation of alternative farming systems at the scale of a small nation such as Ghana.     

Soil quality indicators under continuous cropping systems in the Argentinean Pampas

Over the last two decades, soil cultivation practices in the southern Argentinean Pampas have been changing from a 7 year cash-crop production system alternated with 2–3 years under pasture, to a continuous cropping system. A better understanding of the impact of the period of time a field has been under continuous cropping on a broad spectrum of soil properties related to soil quality is needed to target for sustainable cropping systems. The objectives of this study were to: (i) assess the relationship between physical and chemical soil parameters related to soil quality and (ii) identify soil quality indicators sensitive to soil changes under continuous cropping systems in the Argentinean Pampas.

Correlation analysis of the 29 soil attributes representing soil physical and chemical properties (independent variables) and years of continuous cropping (dependent variable) resulted in a significant correlation (p < 0.05) in 78 of the 420 soil attribute pairs. We detected a clear relationship between hydraulic conductivity at tension h (K_h) and structural porosity (ρ_e); ρ_e being a simple tool for monitoring soil hydraulic conditions.

Soil tillage practice (till or no-till) affected most of the soil parameters measured in our study. It was not possible to find only one indicator related to the years under continuous cropping regardless of the cultivation practice. We observed a significant relationship between years under continuous cropping and K_h under no-till (NT) and wheat fallow (p < 0.001, R² = 0.70). Under these conditions, K₋₄₀ diminished as the number of years under continuous cropping increased.

The change in mean weight diameter (CMWD) was the only physical parameter related to the number of years under continuous cropping, explaining 36% of the variability in the number of years under continuous cropping (p < 0.001) The combination of three soil quality indicators (CMWD, partial R² = 0.38; slope of the soil water retention curve at its inflexion point (S), partial R² = 0.14 and cation exchange capacity (CEC), partial R² = 0.13) was able to explain, in part, the years under continuous cropping (R² = 0.65; p value > 0.001), a measure related to soil quality.     

No-till effects on organic matter, pH, cation exchange capacity and nutrient distribution in a Luvisol in the semi-arid subtropics

No-till (NT) system for grain cropping is increasingly being practised in Australia. While benefits of NT, accompanied by stubble retention, are almost universal for soil erosion control, effects on soil organic matter and other soil properties are inconsistent, especially in a semi-arid, subtropical environment. We examined the effects of tillage, stubble and fertilizer management on the distribution of organic matter and nutrients in the topsoil (0–30 cm) of a Luvisol in a semi-arid, subtropical environment in southern Queensland, Australia. Measurements were made at the end of 9 years of NT, reduced till (RT) and conventional till (CT) practices, in combination with stubble retention and fertilizer N (as urea) application strategies for wheat (Triticum aestivum L.) cropping.

In the top 30 cm depth, the mean amount of organic C increased slightly after 9 years, although it was similar under all tillage practices, while the amount of total N declined under CT and RT practices, but not under NT. In the 0–10 cm depth, the amounts of organic C and total N were significantly greater under NT than under RT or CT. No-till had 1.94 Mg ha⁻¹ (18%) more organic C and 0.20 Mg ha⁻¹ (21%) more total N than CT. In the 0–30 cm depth, soil under NT practice had 290 kg N ha⁻¹ more than that under the CT practice, most of it in the top 10 cm depth. Microbial biomass N was similar for all treatments. Under NT, there was a concentration gradient in organic C, total N and microbial biomass N, with concentrations decreasing from 0–2.5 to 5–10 cm depths.

Soil pH was not affected by tillage or stubble treatments in the 0–10 cm depth, but decreased significantly from 7.5 to 7.2 with N fertilizer application. Exchangeable Mg and Na concentration, cation exchange capacity and exchangeable Na percentage in the 0–10 cm depth were greater under CT than under RT and NT, while exchangeable K and bicarbonate-extractable P concentrations were greater under NT than under CT.

Therefore, NT and RT practices resulted in significant changes in soil organic C and N and exchangeable cations in the topsoil of a Luvisol, when compared with CT. The greater organic matter accumulation close to the soil surface and solute movement in these soils under NT practice would be beneficial to soil chemical and physical status and crop production in the long-term, whereas the concentration of nutrients such as P and K in surface layers may reduce their availability to crops.     

有机农业的环境效益评估

常规农业所带来的环境破坏影响越来越被人们所认识。有机农业作为一种新型农业发展模式 ,以保持农业可持续发展和环境影响最小化为其基本原则 ,近 10 a在全球得到迅速发展和推广。与常规农业相比 ,有机农业的环境破坏风险较低。介绍了有机农业的发展现状 ,并就有机农业可能影响到的水环境、土壤环境、大气环境、生物多样性以及人类健康等方面进行探讨 ,以全面评估有机农业的环境效益     

长期施用氮磷和有机肥对不同种植体系土壤有效硫累积的影响

以22年定位试验为基础,研究了长期施用氮磷和有机肥（NPM）对不同种植体系土壤有效硫在剖面上分布与累积状况。结果表明,在60–80 cm土层各处理出现第一个累积峰,累积峰值为:粮饲轮作31.3、玉米连作29.2、小麦连作27.9、粮豆轮作25.6、苜蓿连作24.0 mg/kg;在140–180 cm 土层各处理又出现有效硫的第二个累积峰,累积峰值为:粮饲轮作44.7、粮豆轮作43.1、小麦连作41.0、玉米连作39.7、苜蓿连作36.5 mg/kg。第二累积峰值均大于第一累积峰值。0–200 cm土层有效硫总累积量粮饲轮作高达746.3 kg/hm2,其次为玉米连作640.6、粮豆轮作为638.3、小麦连作为622.4、苜蓿连作最小为557.3 kg/hm2。长期施用磷肥和有机肥是有效硫在土壤中累积的主要因素,有效硫在土壤剖面上有向深层迁移的趋势。不同作物对硫的吸收利用差异和不同种植方式对有效硫的累积与分布产生影响。     

Effects of organic versus conventional arable farming on soil structure and organic matter dynamics in a marine loam in the Netherlands

Abstract. We compared the effects of conventional and organic arable farming on soil organic matter (SOM) content, soil structure, aggregate stability and C and N mineralization, which are considered important factors in defining sustainable land management. Within one soil series, three different farming systems were selected, including a conventional and an organic arable system and permanent pasture without tillage. The old pasture represents optimal conditions in terms of soil structure and organic matter inputs and is characterized by high earthworm activity. More than 70 years of different management has caused significant differences in soil properties. SOM content, mineralization, earthworm activity and water-stable aggregation decreased as a result of tillage and arable cropping when compared with pasture, but were significantly greater under organic farming than under conventional farming. Total SOM contents between 0 and 20 cm depth amounted to 15, 24 and 46 g kg⁻¹ for the conventional arable, organic arable and permanent pasture fields, respectively. Although less sensitive to slaking than the conventionally managed field, the soil under organic farming was susceptible to compaction when high pressures were exerted on the soil under wet conditions. The beneficial effects of organic farming are generally associated with soil biochemical properties, but soil physical aspects should also be considered. Depending on soil type and climate, organic farmers need to be careful not to destroy the soil structure, so that they can enjoy maximum advantage from their organic farming systems.     

Soil C, N and crop yields in Alabama's long-term ‘Old Rotation' cotton experiment

The Old Rotation cotton experiment at Auburn, Alabama, is the oldest, continuous cotton experiment in the world (cf. 1896). Long-term cropping systems provide a unique opportunity to observe the effects of 100 years of cropping on soil organic carbon (SOC). The objective of this paper was to summarize limited data on SOC and N cycling in this historic experiment. Soil organic C has been measured on the 13 plots (6 cropping systems) in 1988, 1992 and 1994. Long-term planting of winter legumes with no other source of N applied resulted in higher SOC (9.5 g C kg⁻¹) in the plow layer (0–20 cm depth) compared to continuous cotton with no winter cover crops (4.2 g C kg⁻¹). A 3-year rotation of cotton–winter legumes–corn–small grain–soybean resulted in 12.1 g C kg⁻¹. There was a significant (P<0.05), quadratic cotton yield response (R²=0.54) to increasing SOC. Winter legume cover crops supplied between 90 and 170 kg N ha⁻¹. Where no N has been applied in fertilizer or from a legume crop, annual N removal in the cotton crop is around 13 kg ha⁻¹, about the same as that fixed in precipitation.     

Earthworms in a 15 years agricultural trial

Alternative cropping systems have been proposed to enhance sustainability of agriculture, but their mid and long-term effects on soil biodiversity should be studied more carefully. Earthworms, having important agro-ecological functions, are regarded as indicators of soil biological health. Species composition, abundance, and biomasses of earthworms were measured in autumn 2005–2007 (period 1) and 2011–2013 (period 2) in a trial initiated in 1997 near Paris, France. A conventional, an organic and a direct seeded living mulch-based cropping systems were compared. Earthworms were sampled in a wheat crop by combining the application of a chemical expellant and hand-sorting.In period 1, earthworm abundance did not usually differ in the three cropping systems, but sometimes it was higher in the conventional system. Mean total abundance was 122, 121 and 149 individuals m⁻² in period 1 and 408, 386 and 216 in period 2 in the organic, living mulch and conventional systems respectively. While earthworm abundance and biomass increased slightly in the conventional system between the two periods, they at least tripled in the other two systems. This was mainly due to the species Aporrectodea caliginosa and Aporrectodea longa in the living mulch cropping system, and to A. caliginosa, Lumbricus castaneus, Lumbricus terrestris and A. longa in the organic system.After at least 14 years, organic and living mulch cropping systems contained between 1.5 and 2.3 times more earthworms than the conventional system. Considering the inter-annual variations in earthworm communities due to climatic conditions and cultural practices, earthworm communities should be assessed over several years before conclusions can be drawn. Moreover, since changes in cultural practices may take a long time to affect earthworm communities, mid and long-term trials are needed to assess the effects of cropping systems on soil biodiversity.     

”The principles of rational agriculture” by Albrecht Daniel Thaer (1752–1828). An approach to the sustainability of cropping systems at the beginning of the 19th century

The identification of quantitative fertility indicators for evaluating the sustainability of cropping and farming systems has become a major issue. This question has been extensively studied by the German agronomist Albrecht Daniel Thaer at the beginning of the 19^h century. In this paper Thaer's work is set in its historical background, from the end of the 16^th century (Palissy, 1580) to the middle of the 19^th century (Liebig, 1840). Then the paper focuses on Thaer's quantitative and complex fertility scale (expressed in “fertility degrees”), which was based on soil properties, on the requirement of nutrients by plants, and on the cropping system (including crop rotation). Thaer expressed soil fertility and economic results as a function of rye production in “scheffel of rye per journal” (ca. 200 kg per hectare). He also proposed a scale to describe the intrinsic fertility of soil. Thaer used this approach to assess the effect of major German cropping systems on soil fertility. He applied it to eight theoretical systems and nine existing systems in a true modeling approach. Thaer completed the fertility evaluation for the nine existing systems with a detailed economical analysis commenting the limits and potentialities of each system. Thaer's approach was used with success during half a century as it combined numerous empirical findings on soils and fertilization with organic substances in a sophisticated model. Unfortunately and despite effective practical applications, the scientific foundations of Thaer's “Humus Theory” proved definitively false as soon as 1840 when Sprengel and Liebig published on mineral nutrition of plants. Thaer's work deserves to be rediscovered since it approaches the modern issue of the sustainability of cropping and farming systems.     

Evaluation of soil health in organic vs. conventional farming of basmati rice in North India

Conventional agricultural practices that use excessive chemical fertilizers and pesticides come at a great price with respect to soil health, a key component to achieve agricultural sustainability. Organic farming could serve as an alternative agricultural system and solve the problems associated with the usage of agro‐chemicals by sustainable use of soil resources. A study was carried out to evaluate the impact of organic vs . conventional cultivations of basmati rice on soil health during Kharif (rainy) season of 2011 at Kaithal district of Haryana, India, under farmers' participatory mode. Long‐term application of organic residues in certified organic farms was found to improve physical, chemical, and biological indicators of soil health. Greater organic matter buildup as indicated by higher soil organic carbon content in organic fields was critical to increase soil aggregate stability by increasing water holding capacity and reducing bulk density. Proper supplementation of nutrients (both major and micro nutrients) through organic residue addition favored biologically available nutrients in organic systems. Further, the prevalence of organic substrates stimulated soil microorganisms to produce enzymes responsible for the conversion of unavailable nutrients to plant available forms. Most importantly, a closer look at the relationship between physicochemical and biological indicators of soil health evidenced the significance of organic matter to enzyme activities suggesting enhanced nutrient cycling in systems receiving organic amendments. Enzyme activities were very sensitive to short‐term (one growing season) effects of organic vs . conventional nutrient management. Soil chemical indicators (organic matter and nutrient contents) were also changed in the short‐term, but the response was secondary to the biochemical indicators. Taken together, this study indicates that organic farming practices foster biotic and abiotic interactions in the soil which may facilitate in moving towards a sustainable food future.     

Improving soil organic carbon pools through inclusion of summer mungbean in cereal-cereal cropping systems in Indo-Gangetic plain

Long-term effect of mungbean inclusion in lowland rice-wheat and upland maize-wheat systems on soil carbon (C) pools, particulate organic C (POC), and C-stabilization was envisaged in organic, inorganic and without nutrient management practices. In both lowland and upland systems, mungbean inclusion increased very-labile C (Cfrac₁) and labile C (Cfrac₂) in surface soil (0–0.2 m). Mungbean inclusion in cereal-cereal cropping systems improved POC, being higher in lowland (107.4%). Lowland rice-based system had higher passive C-pool (11.1 Mg C ha^?1) over upland maize-based system (6.6 Mg C ha^?1) indicating that rice ecology facilitates the stabilization of passive C-pool, which has longer persistence in soil. Organic nutrient management (farmyard manure + full crop residue + biofertilizers) increased Cfrac₁ and carbon management index (CMI) over inorganic treatment. In surface soil, higher CMI values were evident in mungbean included cropping systems in both lowland and upland conditions. Mungbean inclusion increased grain yield of cereal crops, and yield improvement followed the order of maize (23.7–31.3%) > rice (16.9–27.0%) > wheat (lowland 7.0–10.7%; upland 5.4–16.6%). Thus, the inclusion of summer mungbean in cereal-cereal cropping systems could be a long-term strategy to enrich soil organic C and to ensure sustainability of cereal-cereal cropping systems.     

Effect of tillage,cropping, and mulching pattern on crop yield,soil C and N accumulation,and carbon footprint in a desert oasis farmland

The desert oasis is one of the major grain production areas in arid land, and many intensive farming practices have been adopted to improve the land utilization in the agriculture system. However, there remains little consensus on how to improve such farming practices for increasing both productivity and environment benefits in this system. A 4-year experiment was conducted in a typical desert oasis farmland to determine the effects of the farming practices on crop yield, soil carbon (C) and nitrogen (N) accumulation, and carbon footprint (CF). The farming practices included two tillage patterns: conventional (CT) and reduced tillage (RT), two cropping patterns: continuous (Con) and rotation cropping (Rot), and two mulching pattern: film (F) and straw mulching (S) with eight combined treatments. The RT did not significant decrease crop yield but increase soil C and N accumulation rate by 59% and 130%, and thus decrease CF for crop production compared with the CT. S can also improve soil C and N accumulation, and cause low CF for crop production, but leading to 14–41% decrease in maize yield compared with F. Rot result in a 14% increase on maize yield also has extra benefit to decrease CF for crop production, but no significant effect on soil C and N accumulation compared with Con. Our study adds a reasonable perspective on how to improve the conventional farming systems in desert oasis, the information about RT, straw mulching, and maize–soybean rotation have positive effect on improving soil quality and decreasing CF for crop production in this desert soil area is critical to develop the sustainable agriculture system in this desert oasis farmland, which both maintaining crop productivity and minimizing negative environmental impacts.     

北方农牧交错带不同农作制度对土壤风蚀因子的影响

不合理的农作制度是引发北方农牧交错带土壤风蚀的重要原因。以内蒙古武川旱农试验区为基地,研究了撂荒制、压青休闲制、粗放轮作制、保护性耕作制4种农作制度对风速、土壤紧实度、地表粗糙度、地表覆盖度、土壤有机质含量、表层土壤含水率、土壤风蚀量等因子的影响。结果表明,保护性耕作能够显著降低土壤风蚀,有效防止土地荒漠化。当前,北方农牧交错带应重点推广保护性耕作制,促进农业生产的可持续发展。     

Changes in soil properties and the availability of soil micronutrients after 18 years of cropping and fertilization

Micronutrient deficiencies are common in many parts of China's Loess Plateau. The objective of this experiment was to study the effects of long-term cropping and fertilization practices on soil properties and micronutrient availability in this region. The field plot experiment began in 1984. It included five cropping systems and four fertilizer treatments. In September 2002, soil samples were collected and soil pH, organic matter content, available P, and CaCO₃ were measured. Total and available Zn, Cu, Mn, and Fe were also determined. The relationship between soil properties and available micronutrients was determined by correlation and path analysis. After 18 years, soil pH and CaCO₃ levels were lower in the cropped and fertilized treatments compared to the fallow treatment. In contrast, soil organic matter and available P levels were higher in cropped compared to fallow treatments. A comparison of unfertilized treatments indicated that available Zn and Cu levels in cropped treatments were lower compared to the fallow treatment, probably due to the removal of these micronutrients from the system through crop uptake and harvest. In contrast, available Mn and Fe levels were higher in cropped treatments compared to the fallow treatment. The impacts of fertilization on available micronutrients varied with cropping systems. Generally, available Zn and Fe were higher in fertilized compared to unfertilized treatments, but available Cu was not significantly influenced by fertilization. Fertilization tended to increase available Mn in continuous wheat and maize, but reduced available Mn in continuous clover and the crop–legume rotation. The total (plant available + unavailable) micronutrient contents were lower in the four cropped-treatments compared to the fallow treatment. The addition of manure or P fertilizer increased total Zn, Fe, and Mn, but had no significant effect on total Cu. The results of correlation analysis and path analysis indicated that soil organic matter exerts a significant and direct effect on the availability of Zn, Mn, and Fe, but has little influence on available Cu. The effects of available P, CaCO₃, and pH on micronutrient availability were indirect, passing through soil organic matter. The results of this study suggest that long-term cropping and fertilization altered several important soil properties and increased the plant available micronutrient content of this loess-derived soil.