Soil Use and Management

We studied the effects of applying different composts (urban organic waste, green waste, manure and sewage sludge), mineral fertilizer and compost plus mineral fertilizer on chemical, biological and soil microbiological parameters over a 12‐year period. The organic C and total N levels in soils were increased by all compost and compost + N treatments. Microbial biomass C was significantly (P ≤ 0.05) increased for some compost treatments. In addition, basal respiration and the metabolic quotient (qCO₂) were significantly higher in all soils that had received sewage sludge compost. The Shannon diversity index (H), based on community level physiological profiling, showed a higher consumption of carbon sources in soils treated with compost and compost + N compared with the control. The utilization of different guilds of carbon sources varied amongst the treatments (compost, compost + N or mineral fertilizer). Cluster analysis of polymerase chain reaction‐denaturing gradient gel electrophoresis patterns showed two major clusters, the first containing the mineral fertilization and compost treatments, and the second, the composts + N treatments. No differences in bacterial community structure could be determined between the different types of compost. However, the results suggest that long‐term compost treatments do have effects on the soil biota. The results indicate that the effects on the qCO₂ may be due to shifts in community composition. In this study, it was not possible to distinguish with certainty between the effects of different composts except for compost derived from sewage sludge.

Increased awareness of the role of soil structure in defining the physical fertility or quality of soil has led to the need for a simple assessment relevant to the environmental and economic sustainability of soil productivity. A test is required that is usable by farmer, consultant and researcher alike. Here an assessment of soil structure quality (Sq) is described which is based on a visual key linked to criteria chosen to be as objective as possible. The influences of operator, tillage and crop type on Sq value were tested. The test takes 5–15 min per location and enough replicates were obtained for statistical comparison of data sets. The assessments of individual operators were influenced to an extent by differences between fields, making the use of multiple operators desirable. Differences in soil management were revealed by the test and related to differences in soil physical properties (bulk density, penetration resistance and porosity) and crop growth. Indicative thresholds of soil management are suggested. The assessment should be viewed as complementary to conventional laboratory assessments of soil structure. Visual soil structure assessment can indicate to the soil scientist where to sample and what soil measurements are likely to be worthwhile.

Abstract. Eleven precipitated phosphates were evaluated as sources of phosphorus (P) for plant growth by comparing their effectiveness with that of monocalcium phosphate, a source of water soluble P that is generally considered to be fully plant available. The precipitated phosphates comprised struvites recovered from waste water discharges (mainly magnesium ammonium phosphate), laboratory synthesised struvites, a synthetic iron phosphate and a recovered calcium phosphate. Precipitating phosphates in these forms could be a way for removing P from waste water before it is discharged to rivers, so reducing the risk of eutrophication. Application to agricultural land would be one potential use for such phosphates. Evaluation was by pot experiments with a sandy loam soil and with a sandy clay loam soil using perennial ryegrass (Lolium perenne) as the test crop. The soils differed in pH (6.6 and 7.1) and in Olsen P (28 and 11 mg L⁻¹). Measured variables were grass dry matter (DM) yield and grass P concentration which were used to calculate offtake of P in the harvested grass. DM yields of ryegrass and P offtakes given by the synthetic and recovered struvites were not significantly different statistically either between themselves or to MCP applied at the same rate. On this basis these struvites could be used to recycle P to similar soils and the effect of the P on crop yield should be similar to that of MCP

Conservation tillage (CT) is an umbrella term encompassing many types of tillage and residue management systems that aim to achieve sustainable and profitable agriculture. Through a global review of CT research, the objective of this paper was to investigate the impacts of CT on greenhouse gas (GHG) emissions. Based on the analysis presented, CT should be developed within the context of specific climates and soils. A number of potential disadvantages in adopting CT practices were identified, relating mainly to enhanced nitrous oxide emissions, together with a number of advantages that would justify its wider adoption. Almost all studies examined showed that the adoption of CT practices reduced carbon dioxide emissions, while also contributing to increases in soil organic carbon and improvements in soil structure.

Abstract. A decision support system to predict the plant availability of nitrogen (N) following organic manure applications to land has been developed, drawing together the latest UK research information on factors affecting manure N availability and losses. The ADAS MANure Nitrogen Evaluation Routine (MANNER) accounts for manure N analysis, ammonia volatilization, nitrate leaching and mineralization of manure organic N. Only a few easily available inputs are required to predict the amount of N volatilized or leached, and the fertilizer N value for the next crop grown. Predictions from MANNER have been evaluated by comparison with independently collected data from a range of experimental studies where pig, cattle and poultry manures were applied to arable crops. Good agreement was found (r² 60–79%, P<0.001), confirming that MANNER can provide a reliable estimate of the fertilizer N value of farm manures spread to arable land under a range of conditions.

Abstract. Geostatistics is basically a technology for estimating the local values of properties that vary in space from sample data. Research and development in the last 15 years has shown it to be eminently suited for soil and ripe for application in soil survey and land management. The basic technique, ordinary kriging, provides unbiased estimates with minimum and known variance. Data for related variables can be incorporated to improve estimates using cokriging. By more elaborate analysis using disjunctive kriging the probabilities of deficiency and excess can be estimated to aid decision.

The variogram is crucial in all geostatistics; it must be estimated reliably from sufficient data at a sensible scale and modelled properly. Once obtained it can be used not only in the estimation itself but also to choose additional sampling sites, improve a monitoring network or design an optimal sampling scheme for a survey. It may also be used to control a multivariate classification so that the resulting classes are not too fragmented spatially to manage.

Abstract. Các cuộc khảo sát tài nguyên đất và đất đai khoa học chỉ có tác động hạn chế đến thực tiễn phát triển và mở rộng công nghệ ở các vùng nhiệt đới. Chúng được cho là không có nhiều liên quan đối với các nông dân tự cấp. Việc không thể đáp ứng các ưu tiên xã hội và văn hóa địa phương là một yếu tố. Các nhà khoa học đất đai cho đến gần đây đã ít chú ý đến sự hiểu biết của người khác về đất hoặc ‘nhân văn đất’. Việc kết hợp kiến thức về đất và tài nguyên đất từ dân tộc bản địa gần đây đã được đề xuất nhằm cải thiện tính liên quan của chúng. Tuy nhiên, một sai lầm phổ biến là áp đặt một mô hình khoa học phương Tây mà không phê phán, điều này có thể bóp méo sự hiểu biết. Kiến thức không thông suốt và không theo ngữ cảnh có thể dẫn đến các can thiệp tiêu cực. Bài báo này chỉ trích ý tưởng hạn hẹp về ‘kiến thức kỹ thuật bản địa’, trích dẫn bằng chứng từ Papua New Guinea, Bangladesh và Indonesia. Trong khi chúng tôi nhận thấy rằng nông dân nhất quán sử dụng một số thông tin tương tự như các nhà khoa học để đánh giá đất, các định nghĩa của họ về đất và các loại hình đất thường mâu thuẫn. Các nhà khoa học xác định các lớp dựa trên một loạt các đặc tính được đánh giá kỹ thuật, trong khi nông dân có thể không làm như vậy. Cách tiếp cận tổng thể hơn của họ cũng góp phần vào sự thiếu kết nối này, thường bao gồm cả các khía cạnh xã hội và văn hóa ngoại lai. Việc sử dụng rộng rãi hơn các khái niệm đất đai bản địa trong việc chuyển giao công nghệ nông nghiệp cũng có thể bị giới hạn bởi một số đặc điểm nội tại của chúng, có xu hướng đặc thù theo vị trí và tương đối theo văn hóa.

Arenosols cover extensive areas in coffee producing, humid tropical countries of Sub‐Sahara Africa (Angola, DR Congo) and Southern America (Brazil). A laboratory experiment was undertaken to examine the potential of using coffee waste to improve the physico‐chemical properties of an Arenosol from DR Congo. The amendment was applied at three rates to the topsoil and incubated in soil columns at field moisture capacity for 24 months. A control without any amendment was integral to the completely randomized experimental design involving three replicates. The soil columns were watered weekly with an amount of distilled water approximating to 87% of the average rainfall. Every 3 months, the soil chemical properties and the fraction of leached water and cations were measured. All application rates raised soil pH above 5.5 within 3 months. Exchangeable Ca, Mg and K showed respectively, 5 to 7‐, 2 to 3‐ and 7 to 14‐fold increases with increasing application rates. Organic C and total N significantly increased within 6 months to ca. 1.5 and 0.12% respectively, inducing a decrease in the C/N ratio from 17 to 13. The combined action of increasing soil pH and organic C contributed to a significant increase in cation exchange capacity. Increases in available P were significant, but temporary, with maximum values attained at 9 months. Coffee waste application significantly increased the fraction of retained soil water from 53% to 60%. It promoted the retention of basic cations, immobilized Mn, but increased the mobility of Fe. Coffee waste has the potential to be used as a liming material, an NPK fertilizer and has the benefits also of increasing water and nutrient retention.