The effect of different rates of potassium (K) fertilizer on the yield and quality of sugar beet was studied in a series of 26 trials on soils of different type and K index between 1992 and 1997. There were few yield responses even though the majority of trials were on soils of low K index, and large quantities of fertilizer were applied (0-600 kg K\ha). Potassium offtakes (kg\ha) in the harvested beet increased asymptotically, not linearly, with yield and were much larger for a given yield on high K index soils than on low index soils. Commercially acceptable concentrations of beet K for processing are in the range 700 to 1000 mg K\100 g sugar. Concentrations in excess of this decrease the amount of sugar crystallized from the extracted juice. They were not greatly affected by large applications of fertilizer K but were strongly influenced by long-established differences in soil exchangeable K (K ex ) due to soil type, previous cropping or manuring history.The asymptotic nature of the K offtake : yield relationship was confirmed by factory tarehouse measurements relating to the national sugar beet crop delivered during the 1993-97 UK processing campaigns. Potassium offtakes generally increased linearly with yield up to 60-70 adjusted t of clean beet\ha, but increased little beyond that. The amount of K removed by a 60-70 t\ha crop of beet varied from 70 kg K\ha on low K index sandy loams to 120 kg K\ha on clay soils of K index 3 and above. Further increases in yield decreased the amount of K in fresh beet from 1n7 to 1n4 kg K\t on low K index soils, and from 3n6 to 2n5 kg K\t on high K index soils.An analysis of data from individual fields of commercially grown sugar beet showed that much of the site and season variation in the K content of beet was due to differences in K uptake driven by K ex , and to differential effects of nitrogen (N) supply on K uptake and sugar yield. Regressions on K ex and total crop N (kg\ha) accounted for c. 30 and 50 % of the variance in beet K content, respectively, and the two together for over 60 %. Total N uptake by the crops ranged from 100 to 550 kg N\ha. The total K content of the crop and the amounts of K in the beet (kg\ha) both increased linearly with crop N over the whole of this range, whereas sugar yield increased asymptotically with total uptakes of N up to 250-300 kg N\ha. Consequently, low yielding crops grown on soils in which N and K were freely available produced beet of poor K quality. However, the asymptotic relationship between beet K (kg\ha) and yield implies that, in many situations, the processing quality of the beet could be improved by increasing yield through better agronomy.
INTRODUCTIONThe natural decay of enteric micro-organisms in soil following the application of sewage sludge, or any other type of faecal manure including livestock wastes, provides a final environmental barrier to the potential transmission of infectious disease. Understanding the survival characteristics of pathogenic micro-organisms in soil is therefore important for managing the potential microbiological risk to human and animal health associated with the use of biosolids as soil amendments in agriculture.In general, enteric organisms are poorly adapted to survival in the environment, and pathogens which are introduced to soil (in sewage sludge) are influenced by climatic and agronomic variables. Soil and environmental factors (including moisture, temperature, sunlight, competitive organisms, nutrients and type of soil) and the method and timing of sludge application, influence the decay of faecal micro-organisms in biosolids treated soil. Crops which are ready to eat from the field are not produced in the UK on recently amended soil, and specified minimum harvesting periods apply to these and other types of crop to allow the natural decay of enteric organisms to control the potential risk of infection".2'.The harvesting restrictions for agricultural land receiving biosolids are matched to the degree of pathogen removal which is achieved by different sludge-treatment processes. Conventionally treated sludge is regarded as having undergone stabilisation by a range of defined treatment methods (e.g. mesophilic anaerobic digestion), to ensure at least a 2 login removal of E. coli, and should contain less than lo5 E. coli per g of dry solids (DS) l3) . (Note: l ogm is used throughout the paperJ The absence of epidemiological evidence linking disease outbreaks in the human populationI4l, or in farm live~tock'~' from the agricultural use of sewage sludge, strongly supports the role and effectiveness of these dual barriers in preventing the potential spread of infectious diseases from re-use on farmland.Enhanced treatment is regarded as virtually eliminating the pathogenic content of sludge, and less-stringent management restrictions are applied when this category of biosolids is spread on farmland, compared with conventionally treated material. However, it could be argued that cropping, planting or harvesting restrictions are unnecessary for this type of biosolids product, because the sludge-treatment process provides a critical control point for managing the microbiological risk from land application. Nevertheless, a minimum 10-month harvesting restriction is a precautionary requirement of the 'safe sludge matrix' for enhanced treated biosolids which are used in fruit, salad and vegetable cultivation and other horticultural applications, consistent with the waiting period which is stipulated in the DirectiveI6'. The time intervals which are required before certain crops can be grown after sludge application have been established on a precautionary basis. However, there are relatively few published data describing ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.