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Fertilizer management in stockless organic vegetable production is strongly affected by external nutrient purchases due to the high nitrogen (N) and potassium (K) requirements of vegetables. However, the database on nutrient flows and budgets in organic vegetable farming in Europe is very limited. Therefore, a survey based on semi-structured interviews was carried out comprising 12 organic horticultural farms in Germany. The results show that three different main fertilizer categories are used as inputs in different ratios by the inventoried farms: (1) base fertilizers (e.g., composts, solid farmyard manures), (2) commercial organic N fertilizers (e.g., keratins or plant products from food production or fermentation processes), and (3) commercial mineral fertilizers (e.g., potassium sulfate), all of which are approved for organic production. Ninety percent of the total nutrient inputs to the farms came from these fertilizers and biological N2 fixation, with the remaining 10% coming from other inputs, such as seeds or growing media. The estimated yearly average total farm budgets were nearly balanced across all farms with moderate surpluses (67.5 kg N ha−1, 2.06 kg P ha−1, and 0.26 kg K ha−1). However, large imbalances were found for most of the individual farms. These imbalances indicate the risk of nutrient accumulation or nutrient depletion in the soil, depending on the fertilization strategy and productivity of the farm. More specifically, increasing N share from base fertilizers led to increased P and K budgets, while strategies based on the use of large amounts of keratins led to the opposite—K and P depletion. We concluded that balanced nutrient management in organic vegetable production systems requires a thorough calculation and should combine the use of base fertilizers, commercial fertilizers with low P content, and increased N supply via BNF. [ABSTRACT FROM AUTHOR]

The global population has now exceeded 8 billion and continues to increase; current estimates are that it will reach 9.4-10.1 billion by 2050. It is estimated that more than 460 million people are still unable to find enough food to live a healthy life. The United Nations has therefore set as its Sustainable Development Goal No. 2 to '...end hunger, achieve food security and improved nutrition, and promote sustainable agriculture.' Can this be achieved in a sustainable way without fertilisers? This paper considers the importance of and need for fertilisers in delivering the nutrients essential for long-term sustainable agriculture, reviewing soil nutrient and pH levels and nutrient balances in the UK, Europe and beyond. Between 13 and 20 essential plant nutrients have been identified. Soils can supply many if not all of these, depending on soil composition, but for the macronutrients at least, not in the quantities that modern high-yielding varieties need. This has resulted in very large inputs of fertilisers, especially nitrogen (N): it has been estimated that, in 2008, N fertilisers were responsible for feeding 48% of the world's population. However, the sometimes inefficient use of fertilisers, especially N and phosphate (P), has resulted in a very large surplus of reactive N (Nr) and P on Earth. Amounts of Nr in soils, water and air are currently estimated as being four times the safe limit, so policy makers and farmers are looking for alternatives to fertilisers, especially N fertiliser. However alternatives to fertiliser N, especially the greater use of biological N fixation, would require major changes in farming, diet and the entire food chain. The likely lower yields risk exporting environmental damage from developed to developing countries, resulting in further degeneration in vulnerable regions of the Global South. It is difficult to see how a sustainable food supply can be achieved without fertilisers when the growing world population demands more and better food. A sustainable agriculture is likely to be dependent on the continued but more efficient use of fertilisers, alongside the recycling of manures and other recyclable materials, with continuously improving good agronomic practices for all nutrients, not just NPK. [ABSTRACT FROM AUTHOR]

Sustainable land management of smallholder farms is crucial for ensuring food security in sub‐Saharan Africa. However, little is known about the nutrient dynamics of smallholder farming systems at the farm level based on primary data. In this study, carbon (C) and nutrient budgets of the home garden system in the Kilimanjaro highlands, where Andosols predominate, were quantified at the farmer's field. We evaluated (1) the soil C and nutrient flow in the main three land‐use blocks (banana (Musa spp.) garden, maize (Zea mays L.) field and grassland) in one representative home garden and (2) the internal flow between farmland and livestock and the external nutrient flow across the inside and outside of the six home gardens. Intensive applications of livestock dung to the banana trees resulted in a positive C budget (7.2 Mg C ha−1 year−1) in the banana garden. Nitrogen loss through the harvesting of feed and crops was almost balanced with the livestock dung application, while nitrogen loss through leaching only accounted for 3% of that applied. Banana productivity has been maintained despite a negative potassium budget (−241 kg K ha−1 year−1), probably owing to the replenished exchangeable potassium from Andosols. In the maize field, the C budget was negative (−1.7 Mg C ha−1 year−1) owing to high organic matter decomposition. Carbon and nutrient budgets in the grassland were all negative. Our results revealed that the village average livestock density (4.4 TLU ha−1: TLU means tropical livestock unit) was sufficient for P, Ca and Mg balance in the home garden, whereas it was not sufficient for N and K balance. Increasing livestock density improved the nutrient balance of the system. However, it is noteworthy that 33%–47% of the feed supplied as C and nutrients was collected from outside the home gardens, suggesting a high reliance on external inflow to fulfil feed demands. In conclusion, intensive livestock dung application to banana cultivation was fundamental for maintaining agricultural productivity to replenish the nutrients lost from the system. At the same time, this system was sustained not only by C and nutrient cycling within the system, but also by transporting resources from the external environment into the system. [ABSTRACT FROM AUTHOR]

The rise in global human population, coupled with the effects of climate change, has increased the demand for arable land. Soil fertility has been the most affected, among other things. Many approaches to soil fertility management have been proposed by studies in Sub-Saharan Africa (SSA); however, the question of sustainability remains. Nutrient monitoring (NUTMON), which combines biophysical and socio-economic features for soil fertility management, gives an in-situ soil fertility status of a given land use system, which ultimately provides guidance in proposing appropriate soil management techniques in a given land use system. In this review, the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) approach was deployed for a systematic search of the literature materials. The review evaluated various studies on nutrient monitoring in SSA soils in order to understand the socioeconomic attributes and their influence on farming systems, as well as nutrient flow and balances. The review identified two dominant smallholder farming systems in SSA: mixed crop-livestock and mixed crop farming systems. Also, this review revealed that most nutrient balance studies in SSA have been done in mixed crop and livestock farming systems. However, regardless of the farming systems, the overall mean nutrient balances in all studies, particularly those of nitrogen (N) and potassium (K), were negative, indicating significant nutrient mining. The review further revealed a vast range of biophysical soil fertility management technologies; however, their adoption has been limited by socio-economic aspects including land ownership, gender, financial position, literacy level, and access to inputs. Therefore, in view of this situation, integrating biophysical and socioeconomic disciplines could address the problem of soil nutrient depletion holistically, thus decreasing the existing negative nutrient balances in the SSA region. [ABSTRACT FROM AUTHOR]

The rise in global human population, coupled with the effects of climate change, has increased the demand for arable land. Soil fertility has been the most affected, among other things. Many approaches to soil fertility management have been proposed by studies in Sub-Saharan Africa (SSA); however, the question of sustainability remains. Nutrient monitoring (NUTMON), which combines biophysical and socio-economic features for soil fertility management, gives an in-situ soil fertility status of a given land use system, which ultimately provides guidance in proposing appropriate soil management techniques in a given land use system. In this review, the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) approach was deployed for a systematic search of the literature materials. The review evaluated various studies on nutrient monitoring in SSA soils in order to understand the socioeconomic attributes and their influence on farming systems, as well as nutrient flow and balances. The review identified two dominant smallholder farming systems in SSA: mixed crop-livestock and mixed crop farming systems. Also, this review revealed that most nutrient balance studies in SSA have been done in mixed crop and livestock farming systems. However, regardless of the farming systems, the overall mean nutrient balances in all studies, particularly those of nitrogen (N) and potassium (K), were negative, indicating significant nutrient mining. The review further revealed a vast range of biophysical soil fertility management technologies; however, their adoption has been limited by socio-economic aspects including land ownership, gender, financial position, literacy level, and access to inputs. Therefore, in view of this situation, integrating biophysical and socioeconomic disciplines could address the problem of soil nutrient depletion holistically, thus decreasing the existing negative nutrient balances in the SSA region.

Rotational rice systems, involving pastures, other crops and/or livestock, are common in temperate South America, exemplified by the rice-pasture-livestock system of Uruguay which combines very high rice yields with tight nitrogen (N) balances. The generally good nutrient use efficiency in these systems provides a template for nutrient management in other mixed farming systems, if the underlying processes can be sufficiently well quantified and understood. Here, we studied N balances in rice–non-rice rotations in a long-term experiment in Uruguay, with the aim of parameterizing and testing the DNDC model of N dynamics for such systems for use in future work. The experiment includes three rotations: continuous rice (RI-CONT), rice-soybean (RI-SOY) and rice-pasture (RI-PAST). We considered 9 years of data on N balances (NBAL), defined as all N inputs minus all N outputs; N surplus (NSURP), defined as all N inputs minus only N outputs in food products; and N use efficiency (NUE), defined as the fraction of N inputs removed in food products. We parameterized DNDC against measured yield and input and output data, with missing data on N losses inferred from the N balance and compared with literature values. The model performance was assessed using standard indices of mean error, agreement and efficiency. The model simulated crop yields and rice cumulative N uptake very well, and soil N reasonably well. The values of NBAL were +45 and−20 kg N ha−1 yr−1 in RI-CONT and RI-SOY, respectively, and close to zero in RI-PAST (−6 kg N ha−1 yr−1). Values of NSURP decreased in the order RI-CONT >> RI-SOY > RI-PAST (+115, +25 and +13 kg N ha−1 yr−1, respectively). Values of NUE (84, 54, and 48% for RI-SOY, RI-PAST, and RI-CONT, respectively) decreased as NBAL increased. The sensitivity of DNDC's predictions to the agronomic characteristics of the different crops, rotations and water regimes agreed with expectations. We conclude that the DNDC model as parameterized here is suitable for exploring how to optimize N management in these systems.

Polyacrylamide (PAM) mitigates soil nutrient depletion and increases nutrient utilization; however, the effect of PAM combined with other amendments have not been tested much under field condition. The objective of our study was, therefore, to identify the best combination of amendments that can improve soil nitrogen (N) and phosphorus (P) balances while maximizing utilization efficiency and profitability under teff cultivation. A field experiment was carried out for 2 years in the midland agroecology of Ethiopia. A total of 24 experimental plots were designed using RCBD with three replications. The treatments were PAM (40 kg ha−1), biochar (B = 8 t ha−1), lime (L = 4 t ha−1), gypsum (G = 5 t ha−1), PAM+B, PAM+L, PAM+G, and a control. N and P inflows from atmospheric deposition, biological fixation, and fertilizers; and outflows by water erosion, leaching, gaseous emissions, and harvested products were monitored in all plots via NUTrient MONitoring approach. Results showed that all the applied soil amendments improved nutrient balances (8–134%) compared with the control. Of the measured outflows, harvested products (43–60%) and water erosion (14–31%) were the major contributors to N depletion, followed by leaching (15–23%) and gaseous emissions (11–13%). Among the soil amendments, PAM+L appreciably reduced P loss from water erosion (61%); and N losses from erosion, leaching, and emissions by 55, 10, and 3%, respectively; and increased N use efficiency by 31% compared with the control. Moreover, PAM+L provided a net benefit much higher compared with others. Thus, application of PAM+L would be an effective strategy for sustainable agriculture, especially in acidic and degraded dryland areas. [ABSTRACT FROM AUTHOR]

Plant demand for K in rice is comparable to nitrogen. With yields and management practices changing, refining K fertility management and decision-making tools is necessary. Our objectives were to determine (1) how soil K balances affect soil K indices, (2) the best soil test indicator of plant K availability, and (3) the relationships between plant and soil K indices. We assessed soil (plow layer) and flag-leaf samples from 55 commercial rice fields in California. Growers provided historical information on K fertility practices, straw management, and yields to develop a soil K balance. A soil K balance average of − 15 kg K ha−1 yr−1 (range: − 72 to 47) suggested an increased likelihood of K infertility; however, K balance was not correlated with soil K indices or flag-leaf K. This, plus the potential for K losses and fixation of surplus K, suggests that attempting to build up soil K may not be an effective strategy. Soil K indices were poorly correlated with plant K, but 1 N NH4OAc-extractable K (Kext) was the best of the K indices tested. Soils that were low in Kext had low clay content, CEC, and K saturation, a high Ca + Mg:K ratio, and showed evidence of K fixation. Soil K varied regionally and may be related to irrigation water and soil parent material. The critical level for Kext (currently 60 mg K kg−1) may need to be revised based on our findings, as there was evidence of K deficiencies above this concentration. [ABSTRACT FROM AUTHOR]

The land allocated for newly opened lowland rice can be from ultisols, oxisols, inceptisols, and potential acid sulfate soils. The study was aimed to evaluate nitrogen (N), phosphorous (P), and potassium (K) inputs – outputs of newly developed lowland rice under different treatments and to validate the N, P, and K recommended applications rate according to N, P, and K balances. The study was conducted in Kleseleon village, Malaka District. Five treatments were tested namely T0: farmers practices, T1: NPK at recommendation rate + Rice straw compost, T2: NPK at recommendation rate + Smart + Rice straw compost, T3: ¾ NPK at recommendation rate + Smart + Rice straw compost, and T4: NPK at recommendation rate + Smart + Rice straw compost. The treatments were arranged in a randomized complete block design with three replications. The nutrient balances were constructed according to the difference between nutrient inputs and losses. The results indicated that there were surplus N, P, and K across the treatments and more than adequate to replace N, P, and K removed by harvest products. The suggested N, P, and K application rates were 100 kg urea, 100 kg SP-36, and 100 kg KCl with the addition of compost 3 Mg ha-1 season-1.

This article describes the intensification process of agriculture and its environmental limits regarding soil fertility in the rural community of Fonsagrada, in the inner region of Galicia in northwestern Spain. It addresses changes in land use, crops, and agricultural productivity between 1750 and 1890, framed within the theory of social metabolism and based on the method of nutrient balances. That technique measures nitrogen, phosphorus, and potassium flows across the landscape within a given agro-ecosystem to assess its biophysical functioning and to detect environmental constraints related to management. The intensification of cropland resulted in net losses of potassium in outlying rough grazing land and hay meadows that served as the sources of cropland nutrients. Agricultural intensification was possible due to the close stabling of livestock, which allowed for more manure availability. Doing so, however, deprived pastureland of nutrient recover through manure deposition, which created a metabolic rift in the agro-ecosystem. [ABSTRACT FROM AUTHOR]

The ecosystem services framework can be used as a way of balancing economic, ecological and societal drivers in land management decision-making processes. As heathland management is typically linked directly to services, the aim of this study was to quantify trade-offs related to the effects of five common heathland management measures (grazing, mowing, burning, choppering, and sod-cutting) using quantitative data from empirical studies within a northwestern heathland in Germany. Besides important services (groundwater recharge and quality, carbon stocks and appreciation by the general public) we included ecosystem functions (balances of nitrogen, phosphorus and major cations) and the net cost of management implementation as trade-off components. We found that all management practices have advantages and disadvantages leading to unavoidable trade-offs. The effect of a management practice on the trade-off components was often closely related to the amount of biomass and/or soil removed during a management cycle (Rannual). Choppering and sod-cutting (large Rannual by involving soil removal) were very good at maintaining a low N system whilst concurrently increasing groundwater recharge, albeit at the cost of all other components considered. If the aim is to preserve heathlands and their associated ecosystem services in the long-term this trade-off is inevitable, as currently only these high-intensity measures are capable of removing enough nitrogen from the system to prevent the transition to non-heather dominated habitat types. Our study, therefore, shows that in order to maintain structural integrity and thereby the service potential a habitat provides, management decision frameworks may need to prioritize ecosystem functioning over ecosystem services. Burning and mowing (low Rannual) were best at retaining phosphorus, cations and carbon and had the lowest costs. Grazing (intermediate Rannual) provided the highest relative benefit in terms of groundwater quality and appreciation. Together these results can help identify management combinations in both space and time, which will be more beneficial for functions and services than management practices considered in isolation. Furthermore, our study assists in recognizing key areas of action for the development of novel management practices and can help raise awareness of the diversity of rare species and potential benefits to people that protected cultural landscapes provide.

Declining soil quality is among the factors leading to low crop yields in Sub-Saharan Africa. In this study, a 2 year on farm field experiment was carried out in Ethiopia to test whether integration of organic and inorganic fertilizer inputs increases soil quality, the nutrient balance and maize yields. Treatment combinations included 2 and 4 t ha−1 of compost (Com) and farm yard manure (FYM), and 50 and 100% of the recommended inorganic fertilizer (RIF). The treatments were laid out on 11 farmer fields where each farm served as a replicate. About 40% yield increase was recorded due to the combined use of 4 t ha−1 of Com along with 50% RIF compared to the 100% RIF. Soil quality was significantly improved in the top 20 cm of the soil due to application of FYM or Com combined with 50% RIF. Carbon and Nitrogen stocks were respectively 86 and 175% higher in the 4 t Com + 50% RIF compared to the control with no significant variation between farms. Further, the N and P partial balances were between 12.2 and 41.6 kg ha−1 year−1 and 10.2 and 17.4 kg ha−1 year−1 for N and P, respectively implying that the sites showed N and P-accumulations over the study period. Results suggest that nutrient depletion can be mitigated in smallholder systems through the use of locally available organic inputs, hence longer-term productivity of smallholders can be sustained. [ABSTRACT FROM AUTHOR]

Aim: To describe food scores that can be interpreted as indicators of the potential effects of a food on health outcomes. Methods: The scores consist of weighted averages of the estimates of the association between a health outcome and nutrient balances. Each food contributes a set of weights depending on its nutrient composition. The nutrient balances of a food's constituents are defined in a manner that is similar to those included in the model from which the estimated associations are obtained. As the balances are based on log‐ratios, the presence of zero observations is problematic, but observations recorded as trace (rounded zeros) can be suitably replaced by a small value. In order to overcome the essential zero problem, we propose a strategy that exploits the flexibility of sequential binary partitioning, a procedure used to define orthogonal balances, and also describe the estimates of the variance and confidence limits of food scores. Results: Data from an Italian population‐based study were used to provide examples regarding serum high‐density lipoprotein and triglyceride levels and waist circumference values, and the scores calculated for some foods or groups of foods are shown. Conclusions: Food scores allow foods to be ranked on the basis of their potential effects on health outcomes and, as they are not directly related to the amount of the food consumed, may be less subject to confounding. The accuracy of the estimates depends on the completeness of the food's nutrient composition: that is, the more complete the nutrient composition, the more accurate the estimate. [ABSTRACT FROM AUTHOR]

This article describes agricultural practices of fertilization in the NW of the Iberian Peninsula between 1750 and 1900, where a leguminous plant called gorse (Ulex Europaeus) was used as bedding for livestock in order to produce manure. During the period examined, this whole region experienced a process of agricultural intensification which resulted in a net loss of nutrients in the soil. Peasants dealt with the increasing nutrient requirements by adapting land and livestock management in order to produce more manure during the second half of the 20th century. However, this was done at the expense of nutrient reserves in extensively managed areas, all of which resulted in an unsustainable agricultural pattern. Our data also suggest that the context of nutrient scarcity could be related to changes in the migration pattern, which started to be more intense after 1850 and preferred distant destinations (America), thus switching from seasonal to permanent stays. [ABSTRACT FROM AUTHOR]

When evaluating the impact of macronutrient intakes on health outcomes, researchers in nutritional epidemiology are mostly interested in two types of information: the relative importance of the individual macronutrients and the absolute effect of total energy intake. However, the usual substitution models do not allow these separate effects to be disentangled. Dietary data are typical examples of compositional data, which convey relative information and are, therefore, meaningfully expressed in the form of ratios. Various formulations of log-ratios have been proposed as a means of analysing compositional data, and their interrelationships when they are used as predictors in regression models have been previously reported. This note describes the application of distinct log-ratio transformations to the composition of dietary macronutrients and discusses the interpretative implications of using them as explanatory variables in regression models together with a term for the total composition (total energy intake). It also provides examples that consider serum glucose levels as the health outcome and are based on data coming from an Italian population-based study. The log-ratio transformation of dietary data has both numerical and conceptual advantages, and overcomes the drawbacks of traditional substitution models.

‘Esmeralda’ is an orange fleshed peach cultivar primarily used for juice extraction and secondarily used for the fresh fruit market. Fruit yield and quality depend on several local environmental and managerial factors, mainly on nitrogen, which must be balanced with other nutrients. Similar to other perennial crops, peach trees show carryover effects of carbohydrates and nutrients and of nutrients stored in their tissues. The aims of the present study are (i) to identify the major sources of seasonal variability in fruit yield and qu Fruit Tree Department of Federal University of Pelotas (UFPEL), Pelotas 96010610ality; and (ii) to establish the N dose and the internal nutrient balance to reach high fruit yield and quality. The experiment was conducted from 2014 to 2017 in Southern Brazil and it followed five N treatments (0, 40, 80, 120 and 160 kg N ha−1 year−1). Foliar compositions were centered log-ratio (clr) transformed in order to account for multiple nutrient interactions and allow computing distances between compositions. Based on the feature ranking, chilling hours, degree-days and rainfall were the most influential features. Machine learning models k-nearest neighbors (KNN) and stochastic gradient decent (SGD) performed well on yield and quality indices, and reached accuracy from 0.75 to 1.00. In 2014, fruit production did not respond to added N, and it indicated the carryover effects of previously stored carbohydrates and nutrients. The plant had a quadratic response (p < 0.05) to N addition in 2015 and 2016, which reached maximum yield of 80 kg N ha−1. In 2017, harvest was a failure due to the chilling hours (198 h) and the relatively small number of fruits per tree. Fruit yield and antioxidant content increased abruptly when foliar clrCu was >−5.410. The higher foliar P linearly decreased total titratable acidity and increased pulp firmness when clrP > 0.556. Foliar N concentration range was narrow at high fruit yield and quality. The present results have emphasized the need of accounting for carryover effects, nutrient interactions and local factors in order to predict peach yield and nutrient dosage.

Assessment of the ruminant livestock feed sources availability, existing feeding practices, and nutrient balances was embarked at different zones of Gurez valley of Kashmir in two major seasons (summer and winter). A baseline survey was conducted to obtain the information in three zones, viz., Lower, Middle and Upper Gurez. The study was carried out in three villages in each zone where seven farmer families per village were selected randomly for the study. A total of 63 households owning livestock were interviewed to collect the information and the samples of available animal feeds and fodders fed during the seasons for chemical analysis. Daily nutrient intakes were calculated and compared with the standard requirements to determine the nutrient balances of livestock during the seasons. The main crops cultivated only during summer season were pulses (98.41%), maize (95.24%), and potatoes (90.48%), while few farmers in Lower and Middle Gurez also sow oats (42.86%) and had apple orchards (17.46%), the by-products and wastes of which were utilized as livestock feeds. The only fodder crop cultivated throughout Gurez was maize. During winter, due to very harsh climatic conditions, no agricultural activities are being carried out, as such greenery perishes from the scenario. Feed resources availability to the livestock varied according to the season. Animals relied mainly on natural grazing resources available overabundant during summer and remained undernourished due to very limited feed resources during winter when completely stall-fed. Most of the farmers offered tree foliage (92%) and practiced concentrate feed (86%) supplementation to their animals particularly during winter season (96%). Farmers (87%) were preparing concentrate feed at home by blending ingredients available with them. Only 6% of the farmers supplemented the diet of animals with mineral mixture. Nutrient intakes through different feed resources were in excess during summer, while non-availability of green fodder during winter leads to considerable nutritional deficit in quantity, as well as quality. It is concluded that lack of technical know-how among the animal rearers regarding livestock feeding strategies and winter season feed/fodder scarcity are the major constraints that limit livestock productivity. It is therefore suggested that there is a dire need for nutritional innovations to increase fodder production as well as adoption of fodder conservation and feeding strategies for ensuring year-round availability of animal feeds if sustainable livestock production is to be met in the high Himalaya Gurez valley of Kashmir. [ABSTRACT FROM AUTHOR]

Farm-gate balances for nitrogen (N) and phosphorus (P) were used to determine the potential nutrient surplus and nutrient-use efficiency of three grassland-based milk production systems. These were either full-time grazing (FG) or part-time grazing with indoor feeding of fresh herbage with low (IF) or substantial concentrate allowance (IFplus). Data collected over 3 years were used (a) from 3 × 8 commercial dairy farms, and (b) from a controlled experiment. On FG, IF and IFplus farms, the N surplus (net input minus net output) was 78.6, 75.1 and 138.2 kg N ha− 1 a− 1, respectively, and N use efficiency (NUE; net output/net input) was 0.33, 0.44 and 0.34, respectively. Annual P inputs and outputs were relatively balanced, with a higher P use efficiency (PUE) found for FG (1.19) and IF (0.97) farms than for IFplus farms (0.57). The most important input sources, apart from biological N2 fixation and atmospheric N deposition, were mineral fertilizer N, concentrate N/P in IFplus, and animal manure P. Results from the controlled experiment confirmed most of these findings. In general, the IF provided an efficient nutrient use at a relatively low surplus. Accounting for off-farm losses associated with feed inputs and manure export reduced the system NUE and PUE substantially. The large variability in nutrient-use efficiency among the commercial farms indicates a clear potential for improvement. The average N surplus could be reduced by approximately 40% in reference to the best performing farms in each system. [ABSTRACT FROM AUTHOR]

Since 2003, the regional long-term soil monitoring network (SMN) Schleswig–Holstein (SH) includes an intensive monitoring program (I-BDF) with (sub-)annual measurements at four sites. This is the first study investigating the benefits of this SMN where study sites are no experiments but managed by independent farmers. The main objective of this study was to investigate whether, and under which circumstances, annual soil carbon and nutrient measurements are more beneficial within a soil monitoring network than common five- to ten-year measurements using modeling and nutrient balances. Soil measurements (stocks of soil organic carbon (SOC), Ntot, P and Mg), weekly leachate-NO3–N and management data were used for comparison. C and N changes were modeled with DNDC (DeNitrification–DeComposition); P and Mg were calculated as full nutrient balances and compared to the observations using performance metrics. The results show that DNDC could reproduce the long-term trend of SOC and Ntot well, but this could also be by coincidence as the type of trendline depended on the starting year. The model results could not depict measured short-term variations in soil which were due to field heterogeneities caused by farm management. NO3-N leaching was strongly overestimated when organic fertilization and stronger rainfall occurred. Comparing stock changes with nutrient balances revealed that, in several cases, long-term trends could be shown to a limited extent and reproduced only very few short-term changes and variations. The results suggest that only annual soil property measurements can depict the soil's variability and contribute to the identification of the true long-term trend. [ABSTRACT FROM AUTHOR]

Three experiments were carried out to study whether a gestation diet, a simple transition diet, or a lactation diet is the best choice in late gestation and when sows preferably should be transferred to a high crude protein (CP) lactation diet. In experiment 1, 35 sows were fed either a gestation diet (12.1% CP), a lactation diet (15.9% CP), or a 50/50 mix (simple transition diet; 14.0% CP) from 6 d before parturition until parturition, to study the impact on farrowing and colostrum performance. In experiment 2, 90 sows were studied from 6 d before parturition until weaning at day 24 and they were fed one of five strategies: a gestation diet until day 3 or day 10 of lactation (strategy 1 and 2) and then lactation diet; a simple transition diet until day 3 or day 10 (strategy 3 and 4) and then lactation diet; or a lactation diet throughout the study (strategy 5). In experiment 3, 124 sows were fed strategy 1 or 5. Sows were weighed and back fat (BF) scanned when entering the farrowing unit and at day 2, 10, 17, and 24. Piglets were weighed at birth and after 24 h, and colostrum production was studied (experiment 1). Litter weight at day 2, 10, 17, and 24 was recorded, milk and blood samples were collected weekly and sow fat and protein mobilization, and balances of energy, N, and Lys were calculated from day 3 to 10 of lactation (experiment 2). Total- and live born piglets, and frequencies of stillbirth and piglet diarrhea were recorded (experiment 3). Feeding sows a gestation diet, a simple transition diet, or a lactation diet showed no evidence of effects on colostrum production or farrowing process (experiments 1 and 3) or lactation performance (experiments 2 and 3). Compared to previous studies, sows had a poor milk yield. Plasma urea was elevated (P < 0.001) indicating CP oversupply prior to parturition in sows fed the lactation diet as compared with the two other diets. According to calculated balances, all dietary strategies supplied insufficient amounts of N and Lys from day 3 to 10, indicating that the best choice is to feed sows with a high CP lactation diet from parturition and onwards. Primiparous sows had a higher plasma insulin concentration (P < 0.01), lower colostrum yield (P < 0.01), and higher frequency of piglet diarrhea (P < 0.001) than multiparous sows. In conclusion, in our conditions (high CP in gestation diet; poor milk yield; restricted feeding in early lactation), sow performance was not compromised by the dietary strategies, but results indicate that primiparous and multiparous sows should be fed differently. [ABSTRACT FROM AUTHOR]

Mixed-crop-livestock farms offer the best conditions for sustainable nutrient management in organic farming. However, if stocking rates are too low, sustainability might be threatened. Therefore, we studied the development of soil organic matter and nutrients as well as crop yields over the first course of a new long-term field experiment with a mimicked cattle stocking rate of 0.6 LU ha−1, which is the actual average stocking rate for organic farms in Germany. In the experiment, we tested the effects of additional compost application to improve organic matter supply to soils, and further, potassium sulfate fertilization for an improved nutrition of fodder legumes. Compost was made from internal resources of the farm (woody material from hedge-cutting). Soil organic matter and nutrient stocks decreased in the control treatment, even though yield levels, and thus nutrient exports, were comparably low. With compost application, soil organic matter and nutrient exports could be compensated for. At the same time, the yields increased but stayed at a moderate level. Potassium sulfate fertilization further improved N yields. We conclude that compost from internal resources is a viable solution to facilitate sustainable organic crop production at low stocking rates. However, we are aware that this option does not solve the basic problem of open nutrient cycles on the farm gate level.

We examine the historical evolution of the farming practices linked to the maintenance of soil fertility in a semi-arid Mediterranean village. We analyse the agroecosystem from a sociometabolic perspective at three different points in time (c.1860, 1959, and 1999), focusing on the estimation of the nutrient balances and connecting the assessment of the belowground sustainability with the aboveground dimension of agroecosystem management. Nutrient balances at the aggregated scale were in greater equilibrium in 1860 and 1959 (with results between -7 and 1 kg ha−1) than in 1999 (with nutrient surpluses over 86 kg ha−1), but at the crop system scale nutrient deficits existed at all three points. We discuss the complexity of sustainable farming management assessing the efficiency, effectiveness, and durability of the fertilization techniques. Our conclusions highlight the unsustainable nature of industrialized agriculture and the value of integrated management of agroecosystems to improve agricultural sustainability. [ABSTRACT FROM AUTHOR]

Nitrogen (N) is a vital input to crop production, but its excess use is a cause of environmental and human health problems in many parts of the world. In the United States (US), as in other nations, reducing N pollution remains challenging. Developing effective N policies and programs requires understanding links between cropland N balances (i.e. N inputs minus N harvested in crops) and potential contributing factors. We present novel insights into these links using a national county-level assessment and propose a criteria-scoring method to inform US N policy and programs. First, we characterize cropland N balances across the US in 2011–2013 and identify counties (∼25%) where N input reductions are less likely to result in crop yield declines. Second, we identify agronomic, environmental, social, demographic, and economic factors correlated with N balance, as well as counties that are underperforming based on these characteristics. Finally, we employ criteria scoring and hot spot analysis to identify 20 spatial clusters of opportunity for improved cropland nitrogen management. These hot spots collectively account for ∼63% of total surplus N balance for croplands but only ∼24% of cropland area in the US. N flows for these hot spots indicate variable opportunities across the US landscape to improve cropland N balances by reducing N fertilizer use, better managing manure N, and/or increasing N use efficiency. These findings can guide future efforts to integrate N balance into regulatory and voluntary frameworks in US policy and programs.

Highlights • A model was developed to evaluate management options under future climate scenarios. • Management systems were evaluated in terms of their nutrient costs. • Nutrient outputs, ecosystem N-P balances, and changes in soil C-N-P were simulated. • Removing harvest residues and reducing rotation length have high nutrient costs. • Climate also has an impact, mainly through an effect of elevated atmospheric CO2. Abstract Intensifying the use of forest biomass to produce fuelwood, through the removal of harvest residues or reductions in rotation length, increases nutrient outputs and can ultimately lead to reduced soil fertility. We developed a modelling approach for the evaluation of different forest management options under future climate scenarios. This approach allows management systems to be evaluated in terms of their nutrient costs by quantifying several variables: nutrient outputs (N, P, K, Ca and Mg) resulting from harvesting, ecosystem N and P balances, and changes in organic C, N and P stocks in the soil. In addition, we calculated a “nutrient cost index” (in kg-harvested-biomass g-exported-nutrients−1). As part of this study, we looked at the effects of harvesting branches, foliage and stumps in addition to tree stems, as well as the effects of changing rotation length in Pinus pinaster , Pseudotsuga menziesii and Fagus sylvatica forest stands, under contrasting Representative Concentration Pathway climate scenarios (RCPs). Comparably to previous studies, our simulations showed that removing harvest residues and, to a lesser extent, reducing rotation length have high nutrient costs. Climate was also found to have an impact, mainly caused by larger amounts of standing tree biomass, and therefore larger biomass harvests and increased nutrient outputs in the scenario which involved elevated atmospheric CO 2. Using contrasting forest management systems and climates, we showed that our modelling approach can be used to guide forest managers in their choice of future silvicultural practices (rotation length, conventional stem-only harvest versus intensive harvest, thinning regime) based on future climate scenarios. Finally, our approach can be used to determine, more accurately than simple allometric relationships, the amounts of nutrients that would need to be applied in order to compensate for losses. [ABSTRACT FROM AUTHOR]

Slurry injection below the maize (Zea mays L.) row may substitute a mineral nitrogen (N) phosphorus (P) starter fertilizer (MSF) and thus reduce nutrient surpluses in regions with intensive livestock husbandry. We investigated the plant P, zinc (Zn), and manganese (Mn) status compared to the current farm practice. In 2014 and 2015 field trials were conducted to evaluate plant nutrient status at different growth stages. Besides an unfertilized control, two slurry injection treatments (±nitrification inhibitor (NI)) were compared to slurry broadcast application plus MSF. In both experiments NI addition significantly increased nutrient concentrations during early growth (6-leaf 2015: +33% P, +25% Zn, +39% Mn). Under P deficiency due to cold weather conditions broadcast application showed higher P uptake until 6-leaf (36-58%), while it was lower at 8-(32%) and 10-leaf (19%) stage compared to slurry injection (+NI). Zn availability was enhanced for slurry injection (+NI) during early growth and Zn and Mn uptakes were higher at harvest. Slurry injection decreased P balances by 10-14 kg P ha-1, while Zn and Mn balances were excessive independent of treatments. Slurry injection (+NI) can substitute a MSF without affecting early growth and enhances the Zn and Mn status. This new fertilizing strategy enables farmers to reduce P surpluses. [ABSTRACT FROM AUTHOR]

International trade of food and feed has facilitated the specialization and agglomeration of agricultural production systems in many countries. Confined animals in specialized production systems are increasingly supplied with soybean and maize, imported from other countries. This has increased animal productivity but has also contributed to spatially decoupled crop and animal production systems. We analyzed the changes in the trade of soybean and maize at the global level in the period 1961-2011, and related these to the changes in livestock density and nutrient balances in the whole food system for 11 selected countries. Export of soybean and maize remained dominated by few countries (mainly USA, Argentina and Brazil) during the period 1961-2011, while the number of importing countries increased. Increases in the import of maize and soybean are positively related with changes in livestock density and N and P balances of national food systems. Imported soybean accounted for 12-36% of the calculated N balance at country level, and imported maize for 0-26%. There were large differences between importing countries; increases in the N surplus ranged from 75 to 306 kg N/ha and in the P surplus from 2 to 49 kg P/ha when the mean livestock density increased 1 LU/ha. This variation is related to differences in nutrient management regulations and to spatial variations in livestock density within countries. Our study contributes to the understanding of the complex relationships between the international trade of animal feed, livestock density and environmental impacts associated with N and P balances. [ABSTRACT FROM AUTHOR]

Fertilizer microdosing is a promising technology to complement traditional fertility management strategies, yet little is known regarding its performance in maize systems in western Africa. This study assessed to what extent the application of fertilizer microdosing to maize in northern Benin may contribute towards improved yields, greater nutrient use efficiency and reduced nutrient mining, in combination or not with various manure management practices. In a 2-year on-station experiment at Ina (northern Benin), four fertilizer options were tested [no fertilizer control, microdosing options 1 (MD1, 23.8 kg N ha −1 , 4.1 kg P ha −1 and 7.8 kg K ha −1 ) and 2 (MD2, 33.1 kg N ha −1 , 8.2 kg P ha −1 and 15.6 kg K ha −1 ), broadcast fertilizer at recommended rate (RR, 76 kg N ha −1 , 13.1 kg P ha −1 , and 24.9 kg K ha −1 )] within five manure strata [manure applied through corralling in the same year (Cor-0) as well as one (Cor-1) and two years (Cor-2) before the experiment, transported manure (TM, 3 t ha −1 ), and no manure (NM)]. On average across all manure strata and years, fertilizer application significantly increased grain yields by 64% for MD1, 81% for MD2 and 93% for RR compared to the unfertilized control. Yields in MD2 were never different from those in RR. Across the manure strata, there was a general tendency for FUEs to decrease from MD1 (8.0–19.0 kg grain kg −1 fertilizer) to RR (4.6-8.0 kg grain kg −1 fertilizer). Maize response to fertilizer microdosing was best in the absence of organic amendments and tended to decrease with increasing fertility. Indeed, the greatest grain yield increases were observed for the NM (+1611 kg ha −1 ) and Cor-2 (+1468 kg ha −1 ) strata, followed by TM (+1258 kg ha −1 ), Cor-1 (+1183 kg ha −1 ) and Cor-0 (+1126 kg ha −1 ). Consequently, FUE was also best in NM plots and lowest in recently corralled plots (Cor-0). Fertilizer-induced yield increases resulted principally from larger numbers of grains per cob (+52% on average) and larger 1000-grain weights (+13%). For the NM and TM strata, the partial nutrient balances for the two cropping seasons ranged between −44 and +21, −24 and −9 and −78 and −45 kg ha −1 year −1 respectively for N, P and K depending on the mineral fertilization treatment. The balances ranged between −17 and +54, −77 and −50 and −345 and −228 kg ha −1 over a three-year corralling cycle, respectively for N, P and K. Except for N applied at the recommended rate, partial nutrient balances were equally or more negative on fertilized plots than on the unfertilized controls, indicating that the tested fertilization options may exacerbate nutrient mining. This was particularly the case for P and K and suggests that microdosing should probably not be used for extended periods. Nevertheless, fertilizer microdosing appears better adapted to the realities of smallholder farmers than the RR while still ensuring very significant yield increases. There is a need to evaluate these nutrient management options in farmer’s fields, taking into account climatic, soil and management conditions to better assess and understand the maize response and the magnitude of nutrient mining and to evaluate its economic benefits and risk. [ABSTRACT FROM AUTHOR]

Organic greenhouse vegetable production is characterized by very high nutrient demands within short growing periods and high nutrient exports via products sold. Therefore, meeting crop nutrient demands and maintaining long-term sustainability in these systems is highly challenging. To gain insight in current practices this study assessed fertilization strategies and nutrient flows of ten organic horticultural farms (22 greenhouses and polytunnels) in Southwest Germany belonging to the two organic farming associations Bioland and Demeter (biodynamic) for a cropping period of three years. Soil samples were taken to analyze plant available phosphorus, potassium, soil organic carbon, pH and salinity. Crop rotations in the greenhouses were very diverse, though focused on tomatoes. Depending on association membership, fertilization was based either on the use of solid animal manures (26.1 Mg ha −1 a −1 ) and composts (7.9 Mg ha −1 a −1 ) for the biodynamic Demeter farms or on commercial complementary fertilizers on the Bioland farms (e.g. keratin products, food industry waste products). All farms showed strong imbalances in their nutrient flows with high average surpluses for all nutrients (197 kg ha −1 a −1 for nitrogen, 47.9 kg ha −1 a −1 for phosphorus, 119 kg ha −1 a −1 for sulfur) except potassium with an average deficit of 143 kg ha −1 a −1 and low nitrogen use efficiencies. In addition, a risk for increased soil alkalinity and salinity existed and concentrations of plant available phosphorus in the soil were very high (average 332 mg phosphorus kg −1 ). The results show that today’s fertilization strategies for organic greenhouses are not sustainable, which calls for a thorough revision of the core ideas on soil fertility in the organic horticultural sector. [ABSTRACT FROM AUTHOR]

A plant stress is related both to deficiency of a particular nutrient and to inadequate relationships between nutrients. The objective of the study was to assess the sugar beet nutritional status in response to sodium chloride (NaCl) application. Plant sampling was conducted at two early stages of beet growth (7-leaf – BBCH 17, and well-developed rosette – BBCH 43). The white sugar yield (WSY) was used as an evaluation criterion. The data used in this study originate from a set of 20 field experiments, conducted in years with a significant shortage of precipitation. Each trial was consisted of control (NPK) and a plot with 50 kg Na ha−1(NPK+Na). The nutrient concentration approach and the Compositional Nutrient Diagnosis, based on centered log ratios (CND-clr), were used to evaluate sugar beet nutritional status. The effect of sodium (Na) was evaluated within two subsets of fields: NR – without, and R – with a significant increase in WSYs. The CND-clr indices for Na increased, but for K, Ca and Mg decreased along with Na application, irrespective of the growth stage and subset of fields. However, Na application improved relation between nutrients in fields responding to sodium application, especially at BBCH 43. [ABSTRACT FROM AUTHOR]

Fertilization with manure is widely adopted by farmers in the semiarid region of northeastern Brazil, although the quantity of available manure is limited. Thus, among other alternatives, gliricidia has been used as an additional source of organic fertilizer. The objective of this study was to evaluate the accumulation and apparent recovery of N, P and K after using different forms of gliricidia and manure application in the intercropping of corn, cowpea and cotton in three crop cycles in the semi-arid northeast region of Brazil. The following treatments were used: gliricidia incorporated into the soil before planting; gliricidia spread on the surface of the soil at 45 days after planting; manure and gliricidia incorporated into the soil before planting; manure incorporated into the soil before planting and gliricidia spread on the surface of the soil at 45 days after planting; manure incorporated into the soil before planting; and no addition of organic fertilizer (control). Accumulations followed the same pattern as biomass production but differed greatly from the concentrations. Low apparent recoveries were obtained in the first and second cycles, and high apparent recoveries were obtained in the third cycle. The nutrient balances indicated that the incorporation of gliricidia before planting or spread on the surface does not meet crop needs. The incorporation of manure as well as manure and gliricidia when applied on the surface, were able to meet growth needs and maintain soil fertility. [ABSTRACT FROM AUTHOR]

Due to growing land scarcity and lack of nutrient inputs, African farmers switched from shifting cultivation to continuous cropping and extended crop area by bringing fragile lands such as river banks and hill slopes into production. This accelerated soil fertility decline caused by erosion, harvesting and insufficient nutrient replenishment. We explored the feasibility to reduce nutrient depletion by increasing nutrient utilization efficiencies, while diversifying and increasing food production through the development of integrated aquaculture – agriculture (IAA). Considering the climatic conditions prevailing in Kenyan highlands, aquaculture production scenarios were ideotyped per agro-ecological zone. These aquaculture production scenarios were integrated into existing NUTrient MONitoring (NUTMON) farm survey data for the area. The nutrient balances and flows of the resulting IAA-systems were compared to present land use. The effects of IAA development on nutrient depletion and total food production were evaluated. With the development of IAA systems, nutrient depletion rates dropped by 23–35%, agricultural production increased by 2–26% and overall farm food production increased by 22–70%. The study demonstrates that from a bio-physical point of view, the development of IAA-systems in Africa is technically possible and could raise soil fertility and total farm production. Further studies that evaluate the economic feasibility and impacts on the livelihood of farming households are recommended.

Low crop yields in the savannah zones of West Africa are commonly attributed to rainfall deficits and poor soil fertility. In this study, an assessment was made on how the position of fields belonging to different farm types can explain soil variability and related crop yield gaps in two villages in Burkina Faso, Yilou and Koumbia, located, respectively, in the Sudano-Sahelian and Sudanian agro-ecological zones. In each village, four farm types were identified. Soil fertility was generally poor and use of nutrient inputs low in most of the farmer's fields . As a consequence, yields for most crops were low, but differences among farm types were found, which can be linked to their socioeconomic characteristics that influence the amount of inputs used. Application of fertilizers differed also between fields within farms and tended to be greater on the fields near the homesteads in the village of Yilou, especially for organic fertilizers. At both villages, the rates of N and K inputs were insufficient to compensate for their respective output rates, leading to negative partial nutrient balances . The existence of patchworks of soil fertility gives rise to a wide variation in crop responses to fertilizers. Exploitable yield gaps were substantial and to a large extent related to the low fertility status of soils and sub-optimal fertilizer applications. [ABSTRACT FROM AUTHOR]

Over the years, a scarcity of information on nutrient gains or losses has led to overemphasis being placed on crop yields and economic income as the direct benefits from fertilizer micro-dosing technology. There is increasing concern about the sustainability of this technology in smallholder Sahelian cropping systems. This study was designed in the 2013 and 2014 cropping seasons to establish nutrient balances under fertilizer micro-dosing technology and their implications on soil nutrient stocks. Two fertilizer micro-dosing treatments [2 g hill−1of diammonium phosphate (DAP) and 6 g hill−1of compound fertilizer Nitrogen-Phosphorus-Potassium (NPK) (15-15-15)] and three rates of manure (100 g hill−1, 200 g hill−1and 300 g hill−1) and the relevant control treatments were arranged in a factorial experiment organized in a randomized complete block design with three replications. On average, millet (Pennisetum glaucum (L.) R.Br.) grain yield increased by 39 and 72% for the plots that received the fertilizer micro-dosing of 6 g NPK hill−1and 2 g DAP hill−1, respectively, in comparison with the unfertilized control plots. The average partial nutrients balances for the two cropping seasons were −37 kg N ha−1yr−1, −1 kg P ha−1yr−1and −34 kg K ha−1yr−1in plots that received the application of 2 g DAP hill−1, and −31 kg N ha−1yr−1, −1 kg P ha−1yr−1and −27 kg K ha−1yr−1for 6 g NPK hill−1. The transfer of straw yields accounted for 66% N, 55% P and 89% K for removal. The average full nutrient balances for the two cropping seasons in fertilizer micro-dosing treatments were −47.8 kg N ha−1yr−1, −6.8 kg P ha−1yr−1and −21.3 kg K ha−1yr−1which represent 7.8, 24.1 and 9.4% of N, P and K stocks, respectively. The nutrient stock to balance ratio (NSB) for N decreased from 13 to 11 and from 15 to 12 for the plots that received the application of 2 g DAP hill−1and 6 g NPK hill−1, respectively. The average NSB for P did not exceed 5 for the same plots. It was concluded that fertilizer micro-dosing increases the risk of soil nutrient depletion in the Sahelian low-input cropping system. These results have important implications for developing an agro-ecological approach to addressing sustainable food production in the Sahelian smallholder cropping system. [ABSTRACT FROM PUBLISHER]

Population size and per capita food consumption are assumed to be the two greatest drivers of global environmental change. The intensification of agriculture for food and fiber production, and specially, for energy crops, affects ecosystems due to the use of limited soil resources (e.g. nitrogen, phosphorus, potassium and other macronutrients and micronutrients) which are necessary for their functioning, the release of pesticides, and the conversion of natural ecosystems. However, the location and extent of intensive agriculture and its associated ecological impacts within tropical countries is often well unknown. The purpose of this study is to provide an understanding of the fertilisation practices associated to the phase of sugarcane industrialization in an inter-Andean valley in Colombia. Changes in the nitrogen (N), phosphorus (P) and potassium (K) fluxes were calculated over time (1943, 1984, 1998 and 2010) by using the concept of social metabolism. We applied a nutrient balance model, which was especially created for past agroecosystems (historical studies). The N balances were positive and oscillated between 108 and 98 kg N ha −1 year −1 , with a relatively low N use efficiency (about 63% and 42% for 1943 and 2010, respectively). The main inputs were chemical fertilisation and irrigation, and the main outputs of N included harvested N and leaching due to low N use efficiency and high irrigation flows. By 2010, values of atmospheric deposition rose up to 35.6 kg N ha −1 year −1 , mainly because the nitrate concentrations in rain water were very high in comparison to previous decades. The K and P balances were positive and near zero, which represents an adequate management according to local conditions. The positive N balance in the four analysed years suggests that this element has been historically over applied. This has caused not only high production costs, but also, water and atmospheric pollution. The study of fertilisation systems is, therefore, essential to understand agrarian growth and the process of agricultural intensification. Calculations of N, P and K budgets can be helpful for understanding agroecosystem functioning and proposing more sustainable management strategies. [ABSTRACT FROM AUTHOR]

Studies on the role of nutrient balances in the socioecological transition of agriculture are scarce, particularly in the Mediterranean region where manure availability was low. The role of nutrient balance in this transition was evaluated in three representative localities of the inland Mediterranean region of southern Spain from 1750 to 1900. Changes in cropland distribution, population, manure availability and demand, and nutrient balance at cropland and aggregated scales were assessed. Data suggest that agriculture development around 1750 was limited by manpower. During this period manure availability was higher than demand and municipal balances for nitrogen were positive, whereas they were slightly negative for phosphorus and potassium. During the 19th century, the population increased while livestock numbers and manure availability decreased. Nutrient balances become negative at crop and aggregate scales, indicating that productivity was based on soil mining. This territorial imbalance and soil mining were the main reasons behind the turn-of-the-century crisis which led to the agrarian socioecological transition. [ABSTRACT FROM AUTHOR]

Lag times in reduced nutrient leaching after improved agricultural practices must be assessed to inform management decisions and evaluate their cost-effectiveness. This study estimated the leaching of phosphorus (P) and nitrogen (N) at two scales, a 33.8-ha nested field (data from 1973 to 2011) and an 820-ha agricultural catchment (data from 1992 to 2010). Field management was evaluated along with long-term nutrient trends. Estimates including and excluding nutrient concentrations in the stream under dry catchment conditions (mean 2.5 months year−1) revealed that wastewater contributed 10% of the total P (TP) catchment leaching, mostly in dissolved reactive (DRP) form. More recent flow-proportional sampling at the two scales demonstrated 45% higher particulate P leaching from the field than with discrete water sampling, whereas a past discrete sampling strategy may have overestimated DRP contributions to the stream. The accumulated field P balance was increasingly negative after 1987, whereas crop yields increased. From 1998, the measured accumulated TP leaching from the field was lower than the mean accumulated leaching, considering the estimated downward trend (−10%) over the 38-year study period ( p < 0.05). The average total N (TN) field leaching of 28 kg ha−1 year−1 (1973-2011) was 10% higher than the catchment leaching (1992-2010). The rates and timing of fields N and P fertilization became better adapted to crop requirements over time, and thereafter, a 14% reduction in TN leaching was estimated. No significant trends were estimated for catchment leaching for either TP or TN over the 18-year period, demonstrating an extended lag period for reduced nutrient leaching and the need for long-term monitoring of the effects of pollution mitigation. Copyright © 2014 John Wiley & Sons, Ltd. Highlights Time lag in P and N leaching responses to reduce nutrient surpluses, Close relationship with N export at nested scale, Scale effects in Q indices and PP transport, Point sources of pollution prolonging the time lag for DRP leaching mitigation [ABSTRACT FROM AUTHOR]

Improved agronomic management is important to reduce yield gaps and enhance food security in sub-Saharan Africa. This study was undertaken to understand contributing factors to observed yield gaps for maize in farmer fields and to demonstrate appropriate agronomic survey methods. The study aimed to (1) demonstrate an approach for farm-level agronomic survey, (2) identify key crop production constraints and (3) define the nutrient input and output balances of different fields. Agronomic survey was conducted in 117 farmer fields randomly distributed in a 10 km by 10 km block in Babati, northern Tanzania. A semi-structured questionnaire and production measurements were used to collect data which were analyzed with regression classification and mixed effect models. The exploitable maize yield gap at farm-level reaches up to 7.4 t ha, and only <5 % of fields achieve maize grain yield of 5 t ha. Slope, plant density, distance from homestead, crop variety, timing of planting and period since conversion significantly influenced maize yields. For example, fields on flat land had up to 1.6 t ha more maize grain yield than those on steep slopes while fields with plant density >24,000 plants ha had 900 kg ha more yield than those with less density. At least 52 % of the fields had negative nutrient balances. We conclude that cropping systems used in Babati should be preferentially supplemented with mineral fertilizers while optimizing plant density, increasing manure application and appropriate varietal choice in order to reduce the yield gaps. [ABSTRACT FROM AUTHOR]