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Nutrient additions to intensive agricultural systems range from inadequate to excessive—and both extremes have substantial human and environmental costs. Nutrient cycles link agricultural systems to their societies and surroundings; inputs of nitrogen and phosphorus in particular are essential for high crop yields, but downstream and downwind losses of these same nutrients diminish environmental quality and human well-being. Agricultural nutrient balances differ substantially with economic development, from inputs that are inadequate to maintain soil fertility in parts of many developing countries, particularly those of sub-Saharan Africa, to excessive and environmentally damaging surpluses in many developed and rapidly growing economies. National and/or regional policies contribute to patterns of nutrient use and their environmental consequences in all of these situations ( 1 ). Solutions to the nutrient challenges that face global agriculture can be informed by analyses of trajectories of change within, as well as across, agricultural systems.

Though awareness of fertilizer application has increased over time, low nutrient use efficiency is still a major limiting factor for eucalyptus plantations in India. A study was carried out to understand the nutrient dynamics under different soil fertility conditions by omission of macro nutrients (alone or in combination) and its comparison with balanced nutrient application (NPK) in short rotation Eucalyptus camaldulensis in southern India. This study revealed two phases of nutrient accumulation. The juvenile phase was characterised by an increase in nutrient uptake till canopy closure followed by a phase when the nutrient demand declined. The nutrient partitioning in different tree components changed with age. The rate of accumulation of N and K decreased in the order: leaves > bark > branches > wood > underground parts. The rate of accumulation of P, Ca and Mg decreased in the order: bark > leaves > branches > underground parts > wood. Balanced nutrient application gave 79% higher wood yield than control (no nutrient supply). This study conceptually and quantitatively compares the soil fertility regimes and explores the effect of nutrient limitation at the plant and plant-soil-level. Study also highlights the role of efficient nutrient management for sustainability of plantations, and ways to maximize yield, and improve soil nutrient balance at harvest.

Alleviation of poverty and achievement of zero-hunger target and food security are significant challenges faced by agricultural planners worldwide. Improving many agronomic approaches, which have drastic effects on crop growth and yield, is urgently needed to report this aim. Replacement of a part of chemical fertilizers by organic manure through a simple technique of using minimum effective dose of sufficient and balanced quantities of organic and inorganic fertilizers in combination with specific microorganisms, called INM, has a bright solution in this area. Recently, several investigators reported that integrated use of chemical fertilizers with organic manure is becoming a quite promising practice not only for maintaining higher productivity but also for greater stability to crop production. In addition, INM acts as a source of energy, organic carbon, and available nitrogen for the growth of soil microbes and improvement of physical properties of soil, and also have great residual effect on subsequent crops. So, the key component of the INM goal is to reach the eco-friendly practice through the harmonious properties of both sources by making a combination that can be used for decreasing the enormous use of chemical fertilizers and accreting a balance between fertilizer inputs and crop nutrient requirement, maintaining the soil fertility, optimizing the level of yield, maximizing the profitability, and subsequently reducing the environmental pollution. Lastly, INM is a tool that can offer good options and economic choices to supply plants with a sufficient amount of nutrients in need and can also reduce total costs, create favorable soil physiochemical conditions and healthy environment, eliminate the constraints, safeguard the soil nutrient balance, and find safety methods to get rid of agriculture wastes.

Increased phosphorus (P) fertilizer use and livestock production has fundamentally altered the global P cycle. We calculated spatially explicit P balances for cropland soils at 0.5° resolution based on the principal agronomic P inputs and outputs associated with production of 123 crops globally for the year 2000. Although agronomic inputs of P fertilizer (14.2 Tg of P·y⁻¹) and manure (9.6 Tg of P·y⁻¹) collectively exceeded P removal by harvested crops (12.3 Tg of P·y⁻¹) at the global scale, P deficits covered almost 30% of the global cropland area. There was massive variation in the magnitudes of these P imbalances across most regions, particularly Europe and South America. High P fertilizer application relative to crop P use resulted in a greater proportion of the intense P surpluses (>13 kg of P·ha⁻¹·y⁻¹) globally than manure P application. High P fertilizer application was also typically associated with areas of relatively low P-use efficiency. Although manure was an important driver of P surpluses in some locations with high livestock densities, P deficits were common in areas producing forage crops used as livestock feed. Resolving agronomic P imbalances may be possible with more efficient use of P fertilizers and more effective recycling of manure P. Such reforms are needed to increase global agricultural productivity while maintaining or improving freshwater quality.

Background and aims Root exudation can prime microbial synthesis of additional exoenzymes and consequently accelerate organic carbon (C) and nitrogen (N) mineralization. Such exudate induced priming effect (EPE) has been hypothesized to depend on exudate rate and stoichiometry. Little is known about how EPE would affect litter decomposition. We employed a microcosm experiment to evaluate the influence of root exudate on litter nutrient release and microbial enzyme functions. Methods Leaf litters of Pinus massoniana , Quercus variabilis and Robinia pseudoacacia were incubated under two soil conditions (fertile versus barren). Solutions of chemicals often found in root exudates with contrasting C:N ratios were inoculated frequently into the microcosms to simulate exudation. By comparing with a water control, exudate effect was determined. Results In barren soils, exudates with C:N ratio of 10 significantly decelerated C loss of R. pseudoacacia , all N-containing exudates significantly enhanced the N-cycling related enzymes in decomposing Q. variabilis , while C-only exudate accelerated N loss of P. massoniana . In fertile soils, C-only exudate promoted the N-cycling related enzymes in decomposing R. pseudoacacia . Conclusions A stoichiometric C:N constraint on microbial utilization of exudates arose in decomposing recalcitrant litters in barren soil. EPE and its stoichiometric constraint depend on interactions with litter quality and soil condition. The findings arouse the consequences of exudate rate and stoichiometry changes in determining soil nutrient balance.

The present experiment was conducted to assess the impact of fixed and variable doses (using a normalized difference vegetation index-sensor) of nitrogen (N) on wheat yields, nutrient uptake, nitrogen use efficiency, and soil nitrogen balance through the optimization of nitrogen dose. There were 10 treatments based on fixed and variable doses with different splits, and each treatment was replicated three times under a randomized complete block design. The treatments comprised fixed doses of 120 and 150 kg N ha –1 with different splits; variable doses based on sensor readings after application of 60, 90, and 120 kg N ha –1 ; 225 kg N ha –1 as a nitrogen-rich control; and no application of nitrogen as the absolute control. It was revealed that the application of a basal dose of 60 kg N ha –1 and another 60 kg N ha –1 at the crown root initiation stage followed by a sensor-guided N application significantly improved wheat grain yields and grain nitrogen uptake. However, straw nitrogen uptake was highest in N-rich plots where 225 kg N ha –1 was applied. It was found that any curtailment in these doses at basal and crown root initiation stages followed by nitrogen application using a normalized difference vegetation index sensor later could not bring about higher crop yields. On average, wheat crops responded to 152–155 kg N ha –1 in both years of the study. Partial factor productivity along with agronomic and economic nitrogen use efficiency showed a declining trend with an increased rate of N application. Apparent N recovery values were comparable between normalized difference vegetation index sensor-based N application treatments and treatments receiving lesser N doses. Soil N status decreased in all the treatments except the nitrogen-rich strip, where there was a marginal increase in soil N status after the wheat crop harvest in the rotation. Partial nitrogen balance was negative for all the treatments except the control. From these 2-year field trials, it can be concluded that applying a normalized difference vegetation index sensor could be an essential tool for the rational management of fertilizer nitrogen in wheat grown in eastern sub-Himalayan plains.

AIM: To compare the internal balances of nutrients and the rates of nutrient cycling across nine cocoa agroforestry systems consisting of various combination of soil types (Latosols and Cambisols), production systems (cabruca and Erythrina glauca-shade) and fertilization regimes in southern Bahia, Brazil. METHODS: We measured nutrient stocks in litter fall production, in the accumulated litter and fruits. The internal nutrient balance for various simulations was obtained by the following expressions: (1) Balance 1 = litter – fruit (seeds and husks) and (2) Balance 2 = (litter + husks) – seeds. Annual litter decomposition coefficients (k) and subsequent potential of nutrient release were also investigated. The data were analyzed by principal components analysis and by Pearson correlations. RESULTS: There was a high degree of dissimilarity among the cocoa agrosystems in relation to the nutrient cycling and the internal nutrient balance. The mean annual litterfall production ranged from 4.6 to 8.5 Mg/ha, and the amount of accumulated litter ranged from 7.7 to 16.8 Mg/ha. The results showed significant differences in quality among litter from cocoa agroforests; the decomposition coefficient of litter and the subsequent nutrient release were regulated by the litter quality. In general, the cocoa-erythrina system presented a higher capacity to recycle nutrients compared to the cocoa-cabruca system, with the cocoa-erythrina system having the largest transfer rate of nutrients through litterfall, high values for the decomposition coefficient of litter and the lowest values for the Mean Residence Time of nutrients. Cocoa tree leaves functioned as a sink of nutrients, while shade tree leaves functioned predominantly as a source. The nutritional reserves of litter + cocoa fruit husks, with respect only to the nutrients exported in the seeds, the balance was positive for all nutrients (N, P, K, Ca and Mg) in all agroforests, which emphasizes the potential productive capacity of these agroforests to sustain the estimated production in different harvest cycles. CONCLUSIONS: The internal balance of nutrients reflects an agroforests’s productive capacity, which accumulated litter and cocoa fruit husks may be important nutrient sources that could enable the development of fertilizer recommendation systems aimed at increasing the efficiency of fertilizer use and at maintaining soil fertility in cocoa agroforests. Therefore, further research is needed to develop nutritional balance systems integrating litter + fruits stock and other nutrient pathways (e.g., soil quality, biological N fixation, leaching), which were not measured, for making recommendations regarding liming and fertilizers that are suitable for highly complex biological agrosystems, such as cocoa agroforests that have low levels of elements exported during seed production.

Fertilizer K and P requirements for rice (Oryza sativa L.) can be determined with site-specific nutrient management (SSNM) using estimated target yield, nutrient balances, and yield gains from added nutrient. We used the QUEFTS (QUantitative Evaluation of the Fertility of Tropical Soils) model with >8000 plot-level observations to estimate the relationship between grain yield and nutrient accumulation in above-ground dry matter of irrigated rice with harvest index ≥ 0.4. Predicted reciprocal internal efficiencies (RIEs) at 60-70% of yield potential corresponded to plant accumulation of 14.6 kg N, 2.7 kg P, and 15.9 kg K per tonne of grain yield. These RIEs enable determination of plant requirements for K and P and net output of K and P in harvested grain and removed crop residues at a target yield. Yield gains for nutrient applied to irrigated rice averaged 12% for K and 9% for P for 525 to 531 observations. For fields without certain yield gain, fertilizer K and P requirements can be determined by a partial maintenance approach (i.e., fertilizer input < output in nutrient balance), which considers nutrient supply mediated through soil processes and balances trade-offs between financial loss with full maintenance rates and risk of excessive nutrient depletion without nutrient application. When yield gains to an added nutrient are certain, partial maintenance plus yield gain can be used to determine fertilizer requirements. The SSNM-based approach and algorithms enable rapid development of field-specific K and P management.

Phosphate-solubilizing bacteria (PSB) are microorganisms that can dissolve insoluble phosphorus (P) to accessible forms. This study aimed to screen saline–alkali-tolerant PSB and analyze its growth promoting properties, and evaluate its effects on the growth, quality, soil nutrient balance, and enzyme activities of silage maize in the field. We isolated six phosphate-solubilizing strains from rhizosphere soil of silage maize planted in saline–alkali land, and FC-1 with the best P-solubilizing effect was used for further study. The morphological, physiological and biochemical analysis, and 16S rDNA and housekeeping gene atpD sequencing were performed for identification. FC-1 was identified as Pantoea dispersa and had high P solubility. The phosphate solubility of FC-1 using four P sources ranged from 160.79 to 270.22 mg l−1. FC-1 produced indole-3-acetic acid (IAA) and decreased the pH of the growth media by secreting organic acids, including citric acid, malic acid, succinic acid, and acetic acid. The results of a field experiment indicated that FC-1 treatment increased the height, stem diameter, fresh weight, dry weight, starch content, crude protein content, and total P content of silage maize by 9.8, 9.2, 12.6, 11.7, 12.6, 18.3, and 17.4%, respectively. The nitrogen, potassium, phosphorus, and organic matter contents in the rhizosphere soil of silage maize increased by 29.8, 17.1, 17.9, and 25.3%, respectively; urease, catalase, sucrase, and alkaline phosphatase levels also increased by 24.7, 26.7, 24.0, and 19.5%, respectively. FC-1 promoted the growth of silage maize by improving nutrient metabolism and enzyme activities in saline–alkali soil and may be an effective alternative to fertilizers.

Agricultural nutrient balances have been receiving increasing attention in both historical and nutrient management research. The main objectives of this study were to further develop balance methodologies and to carry out a comprehensive assessment of the functioning and nutrient cycling of 1950s agroecosystems in Portugal. Additionally, the main implications for the history of agriculture in Portugal were discussed from the standpoint of soil fertility. We used a mass balance approach that comprises virtually all nitrogen (N), phosphorus (P) and potassium (K) inputs and outputs from cropland topsoil for average conditions in the period 1951–56. We found a consistent deficit in N, both for nationwide (−2.1 kg.ha −1 .yr −1 ) and arable crops (−1.6 kg.ha −1 .yr −1 ) estimates, that was rectified in the turn to the 1960 decade. P and K were, in contrast, accumulating in the soil (4.2–4.6 kg.ha −1 .yr −1 and 1.0–3.0 kg.ha −1 .yr −1 , respectively). We observed that the 1950s is the very moment of inflection from an agriculture fertilized predominantly through reused N in biomass (livestock excretions plus marine, plant and human waste sources) to one where chemical fertilizers prevailed. It is suggested that N deficiency played an important role in this transition.