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The Brazilian guava processing industry generates 5.5 M Mg guava waste year(-1) that could be recycled sustainably in guava agro-ecosystems as slow-release fertilizer. Our objectives were to elaborate nutrient budgets and to diagnose soil, foliar, and fruit nutrient balances in guava orchards fertilized with guava waste. We hypothesized that (1) guava waste are balanced fertilizer sources that can sustain crop yield and soil nutrient stocks, and (2) guava agroecosystems remain productive within narrow ranges of nutrient balances. A 6-year experiment was conducted in 8-year old guava orchard applying 0-9-18-27-36 Mg ha(-1) guava waste (dry mass basis) and the locally recommended mineral fertilization. Nutrient budgets were compiled as balance sheets. Foliar and fruit nutrient balances were computed as isometric log ratios to avoid data redundancy or resonance due to nutrient interactions and the closure to measurement unit. The N, P, and several other nutrients were applied in excess of crop removal while K was in deficit whatever the guava waste treatment. The foliar diagnostic accuracy reached 93% using isometric log ratios and knn classification, generating reliable foliar nutrient and concentration ranges at high yield level. The plant mined the soil K reserves without any significant effect on fruit yield and foliar nutrient balances involving K. High guava productivity can be reached at lower soil test K and P values than thought before. Parsimonious dosage of fresh guava waste should be supplemented with mineral K fertilizers to recycle guava waste sustainably in guava agroecosystems. Brazilian growers can benefit from this research by lowering soil test P and K threshold values to avoid over-fertilization and using fresh guava waste supplemented with mineral fertilizers, especially K. Because yield was negatively correlated with fruit acidity and Brix index, balanced plant nutrition and fertilization diagnosis will have to consider not only fruit yield targets but also fruit quality to meet requirements for guava processing.

Increased demand for certified organic products has led to an increase in the number of certified organic farms in developing countries. Knowledge of farmer nutrient management practices on certified organic farms in developing countries is limited. Thus, the aim of this study was to investigate the impact of the adoption of certified organic agriculture on farm nutrient flows and nutrient budgets, and evaluate to which degree organic farms comply with organic principles relating to nutrient management. The study is based on five case studies of different types of certified organic farming systems in Brazil, Egypt and China. Farm nutrient flows and nutrient budgets for nitrogen, phosphorous and potassium were created for each farm. Four of the five organic systems studied had nutrient surpluses on the farm budget. The surpluses were of varying magnitude. The main difference between organic and non-organic farm nutrient flows was the replacement of mineral fertilizers with organic inputs. However, the magnitude of nutrient flows were generally similar for organic and non-organic farms. Certified organic farms with positive nutrient budgets had a heavy reliance on external inputs. Continued high dependence on an external supply of nutrients, which typically originate from mineral sources, poses a significant challenge to organic farmers' fulfilment of the principles of organic agriculture.

The Baltic Sea is one of the world’s marine areas well covered by both long-term observations and oceanographic studies. It is also a large coastal area in which eutrophication had already been recognised half a century ago. While the mechanisms of eutrophication are largely understood, several features are less recognised and sometimes neglected, including: a) natural and anthropogenic North-South and East-West nutrient gradients within the drainage basin and marine ecosystems; b) the compensatory potential of the interconnectivity between the Baltic Sea basins; c) long nutrient residence times and high buffer capacity of the system, resulting in slow responses to nutrient load reductions. Particularly important is the interaction of d) naturally occurring saltwater inflows sporadically ventilating deep water layers and e) a partly man-made intensification of biological oxygen consumption. Resulting redox alterations of biogeochemical nitrogen and phosphorus cycles are locked in a “vicious circle” that promotes cyanobacterial nitrogen fixation, thereby hindering nitrogen load reduction and sustaining an elevated trophic state. This tight coupling of natural environmental variation and human impacts complicates both scientific studies and management recommendations. Our primary objective is to describe all these features and mechanisms with the best available data on nutrient loads, and unique estimates of the basin-wide nutrient pools. These data are presented as both long-term time series and empirical nutrient budgets. The analysis is supplemented by results of biogeochemical modelling. A second, more practical objective is to make these time series available to the community.

Nutrient budgeting for cropland is a crucial tool for assessing nutrient mining or excess application. We estimated the nutrient budget of nitrogen (N), phosphorus (P), and potassium (K) in cropland for South Asia during the last five decades (from 1970 to 2018) using equation-based empirical methods. Nutrient budget for the last five decades shows a negative balance of N (3.94 million tons, Mt), P (23.87 Mt), and K (247.23 Mt). Inorganic fertilizer remained the major input source for N and P, and its decadal average share increased for N (from 27.9% to 72.8%) and P (from 72.1% to 94.5%) from 1970 to 2010s and the share of manure, deposition, and crop residue to N, P and K input decreased. Deposition remained a major source of K input and its share decreased from 64.0% to 35.5% during the period. The share of crop removal to the decadal output of N (58.6% to 53.4%) and P (49.0% to 23.1%) decreased, and K (72.5% to 76.0%) increased from 1970 to 2010s. The higher losses of fertilizer N, and accumulation of P and K fertilizers in soils, resulted in decreasing partial factor productivity of N (from 72.2% to 16.9%), P (from 217.0% to 42.2%), and K (from 480.3% to 113.8%) from 1970 to 2018. Nutrient budget helps in identifying the regional imbalance (mining/accumulation) of the major nutrients, it will provide valuable information on the present status of country-level nutrient use for reorientation of their nutrient/fertilizer use policies.

We use a nutrient‐ratio budget method to investigate the relative importance of different nutrient source and sink terms at time‐series Station ALOHA and Bermuda Atlantic Time‐series Study (BATS) in the North Pacific and North Atlantic subtropical gyres, respectively. At mean state conditions over annual and multi‐year time scales, vertical phosphate (PO43–${\\mathrm{P}\\mathrm{O}}_{4}^{3\\mbox{--}}$ ) supply from the subsurface accounts for ∼60% of the total phosphorus supply at both sites. Dissolved organic matter transport and zooplankton excretion are more important phosphorous export pathways than sinking particles at Station ALOHA and BATS. The nutrient‐ratio budget approach provides quantitative, observation‐based constraints on nutrient sources and sinks in the surface ocean, which helps improve our understanding of the biological carbon pump in oligotrophic oceans. Plain Language Summary In this study, we explore the cycling of nutrients that support primary production in the surface ocean and its subsequent export to depth using observed elemental ratios of nitrogen to phosphorus for various nutrient sources and sinks. We use nutrient observations from long‐term oceanographic time‐series studies at Station ALOHA near Hawaii and the Bermuda Atlantic Time‐series Study near Bermuda. We assume that both stations are under conditions of steady state in which nutrient concentrations are not changing over long time periods, and therefore, that the nitrogen‐to‐phosphorus ratio between inputs and outputs should be balanced. We apply a mathematical model to estimate the relative contribution of each input and output term. Our results suggest that nutrient input is driven primarily by the vertical transport of subsurface water at both study sites. Nutrient output (loss) is driven by the gravitational sinking of large particles, the downward mixing of dissolved constituents, and the active transport of migrant animals. The loss due to the latter two processes is more important in magnitude. Our simple methodology provides quantitative, observational constraints of nutrient sources and sinks to the upper ocean, contributing improved understanding of the biological carbon pump in the oligotrophic subtropical ocean. Key Points A nitrogen‐to‐phosphorus ratio budget method is used to quantify nutrient sources and sinks at two subtropical ocean study sites Vertical phosphate supply is the dominant source of phosphorus to the surface of the North Pacific and the North Atlantic study site Dissolved organic phosphorus transport and zooplankton excretion are more important than sinking particles as nutrient sinks

Crop-livestock production systems are the largest cause of human alteration of the global nitrogen (N) and phosphorus (P) cycles. Our comprehensive spatially explicit inventory of N and P budgets in livestock and crop production systems shows that in the beginning of the 20th century, nutrient budgets were either balanced or surpluses were small; between 1900 and 1950, global soil N surplus almost doubled to 36 trillion grams (Tg)·y −1 and P surplus increased by a factor of 8 to 2 Tg·y −1 . Between 1950 and 2000, the global surplus increased to 138 Tg·y −1 of N and 11 Tg·y −1 of P. Most surplus N is an environmental loss; surplus P is lost by runoff or accumulates as residual soil P. The International Assessment of Agricultural Knowledge, Science, and Technology for Development scenario portrays a world with a further increasing global crop (+82% for 2000–2050) and livestock production (+115%); despite rapidly increasing recovery in crop (+35% N recovery and +6% P recovery) and livestock (+35% N and P recovery) production, global nutrient surpluses continue to increase (+23% N and +54% P), and in this period, surpluses also increase in Africa (+49% N and +236% P) and Latin America (+75% N and +120% P). Alternative management of livestock production systems shows that combinations of intensification, better integration of animal manure in crop production, and matching N and P supply to livestock requirements can effectively reduce nutrient flows. A shift in human diets, with poultry or pork replacing beef, can reduce nutrient flows in countries with intensive ruminant production.

The rapid expansion of rubber tree plantations in recent decades has been accompanied by dramatic negative ecological and social impacts. Rubber sector stakeholders consequently engaged in sustainable production of rubber. Despite the lack of harvest during the immature stage following planting, this period plays a key role in future yields. Management practices, particularly fertilization regimes, are used by farmers to shorten the immature period as much as possible. This entails maintaining or even improving the productivity of existing plantations to face the demand for natural rubber. This review focuses specifically on the immature period of rubber tree plantations, as it is the most critical period for nutrient management. We reviewed available knowledge on fertilization practices, soil management, and nutrient dynamics in rubber plantations with the goal of developing a nutrient balance approach for this crop. Our review revealed (1) a notable difference between fertilizer recommendations made by technical institutes and those reported in the scientific literature; (2) that even though nutrient diagnostic methods could help growers adapt the fertilization of rubber trees more than 3 years of age, further studies are needed to adapt current methods to the wide range of cultivation areas; and (3) that the nutrient budget approach may be the best way to incorporate the variety of rubber tree cultivation conditions. In conclusion, the nutrient budget method is a promising way to improve the sustainability of rubber plantations through fertilization making it possible to increase nutrient use efficiency. A comprehensive approach based on nutrient budgets requires further in-depth studies to examine nutrient dynamics in a wide range of conditions, including intercropping and logging residue management between clearcutting and replanting.

The Green Revolution rapidly increased India’s food production since the 1960s, but excessive synthetic fertilizer use caused severe environmental problems. Our spatially explicit analysis for 1970–2020 indicates an uneven distribution of the dramatic increase of surpluses of India’s soil N (4.3 to 21.6 Tg N/year) and P budget (0.4 to 3.3 Tg P/year): with high surpluses in e.g., Green Revolution (GR) and South-West (SW) regions, lower surpluses in e.g., North-West (NW) and even local deficits within some other states Nutrient surpluses were growing primarily through increased use of synthetic fertilizers, which resulted in declining nutrient use efficiency, high N and P losses and soil P accumulation, with large regional heterogeneity. Total N loss is determined by the surplus, through “holes in the pipe”, whereby the holes (loss pathways) differ in diameter, as determined by climate, crop, soil, terrain and management. Ammonia volatilization ranged from 16% of the N surplus (NC) to 45% (GR states), and denitrification losses from 50% (NC and SW) to 38% (GR) and 28% (NE). N loss via leaching ranged from 46% (NE), to 22–26% (GR and NC), and 16% (SW), and surface runoff losses between 2% (GR) and 9% (NC). In the period 1970-2020, our estimated soil P accumulation across India amounts to 290 kg P/ha, highest in SW followed by NE and GR states and lowest in NC. The SW region also has the highest surface runoff P loss (40% of its regional budget), followed by NC (53%), NE (34%), and GR (26%). Addressing these regional differences can help developing effective, targeted and region-specific nutrient management strategies while meeting India’s rising food demand.

Nutrient retention is an important process in lake nutrient cycling of lakes and can mitigate lake eutrophication. However, little is known about temporal lake nutrient retention efficiency and it varies due to changes in hydrological, ecological, and nutrient inputs to lake waters. Quantitative information about seasonal lake N and P retention is critical for developing strategies to reduce eutrophication in lake systems. This study investigated TN and TP retention efficiencies and retention masses using water and mass balance calculations, and statistically analyzed the seasonal variability of nutrient retention in Lake Chaohu, China, from 2014 to 2018. Lake Chaohu experienced large amounts of external loads inputs (23.2 g N m −2  year −1 and 1.3 g P m −2  year −1 ), and approximately 58% TN and 48% TP were retained annually. The lake acted more as a sink for N than for P. The mean annual TP retention efficiency decreased ( P  < 0.05) over the study period, indicating that TP retention capacity was gradually exceeded. Seasonal variability of TN and TP retention efficiency was high and ranged from − 18.7 to 144.1% and from − 58.8 to 170.7%, respectively, over the five study years. The internal P loads over the study period were equivalent to roughly 9% of the total external loads. The annual nutrient retention efficiency of TN and TP increased with hydraulic residence time, while water temperature was an essential factor for the contrasting seasonal variation patterns of TN and TP retention efficiencies.

In organic fruit production, permitted fertilisers contain multiple nutrients with stoichiometries differing from the nutrient offtakes of the fruit trees. Furthermore, some pesticides contain nutrients resulting in additional inputs. These conditions may cause unbalanced nutrient supplies and thereby influence the long-term sustainability of the system. An analysis of nutrient management practices in organic apple farms was conducted in three Southern and one Northern German apple-growing region. Data on nutrient inputs (via fertilisers and pesticides) and outputs (via fruit) per orchard were collected along with soil samples from up to five orchards per farm on 19 farms. On average, farmers fertilised 37 kg N and harvested 23 Mg apples per ha and year. Nutrient budgets showed imbalances for N (+ 25 kg ha −1  year −1 ), P (+ 3 kg), K (− 4 kg), Ca (+ 37 kg), Mg (+ 4 kg), S (+ 53 kg), Na (+ 4 kg) and Cl (+ 3 kg). Base fertilisers like compost or manure contributed to higher nutrient inputs due to a larger P and K-to-N-ratio. Commercial organic fertilisers such as keratins or vinasse contained much lower ratios. The main S input sources were pesticides (46 kg). N inputs by base ( p  = 0.06) and commercial ( p  = 0.37) fertilisers had no significant effect on the yield. Balanced nutrition can best be achieved by applying a combination of 20% of the total N demand via base fertilisers, complemented with commercial fertilisers with low element-to-N-ratios (e. g. keratin fertilisers, vinasse or biological N 2 fixation). No correlation was found between soil nutrient status and nutrient budgets. Site conditions and internal field nutrient flows (transfer of the inter-row biomass via mulching into the tree row) had a stronger influence on the soil nutrient content than fertilisation strategy. In addition, fruit orchards showed a spatial differentiation of soil nutrient contents. Elevated P and K contents above the recommended range in the tree row were found in 67% of the orchards, while tendencies of depletion were found in the inter-row area. Mulching schemes which transfer biomass from the inter-row area to the tree row need to be adapted to this condition.