Annual Fertilizer Application Research Articles

Determinants of the Adoption of Additional Livelihoods among Smallholder Cocoa Farmers in the Sefwi Akontombra Cocoa District of Ghana

Although the production of cocoa in Ghana sustains the economy, its quantity has not been stable in the past. This instability in the quantity of cocoa produced can be attributed to climatic conditions and other human-induced factors such as Galamsey. In the Sefwi Akontombra cocoa district, one leading cause of the reduction of cocoa is the infestation of the Cocoa Swollen Shoot Virus Disease (CSSVD). Farmers Business School has been one medium through which farmers are educated on how to make farming a business however, various factors seem to limit farmers decisions to adopt these additional livelihoods. Hence, the main objective of the study was to explore the various factors that hindered farmers' decision to adopt additional livelihoods. Employing the simple random sampling method, 410 farmers were selected for the study. A binary Logistic regression model was employed to establish relationships between Additional Livelihoods and the various factors that hinder its adoption. The study revealed that Good Agronomy Practices such as annual pruning, annual fertilizer application, and annual pollination were practiced by farmers. Regardless of this GAP, the quantity of cocoa beans produced annually per hectare has been reduced from 2017 to 2021. The study also revealed that farmers who have adopted additional livelihoods have their income level increased, food security, and general livelihood increased. Most of the farmers (70.7%) were not regular at Farmers Business School which seems to be a reason why the majority have not adopted additional livelihoods. Other factors such as environmental, socio-cultural, and economic were significant at 0.05 significant level. However, personal factors were not significant at either 0.1, 0.05, or 0.01. The study recommends that farmers should be frequent participants in Farmers Business School.

Impact of Climate Warming on Paddy Soil Organic Carbon Change in the Sichuan Basin of China

Climate warming can increase soil temperature and lead to soil carbon release, but it can also increase soil organic carbon by increasing primary productivity. Cropland soils are considered to have a huge potential to sequester carbon; however, direct observations for the responses of cropland soil organic carbon to climate warming over broad geographic scales are rarely documented. Paddy soil is one of the important cultivated soils in China. Based on the data of 2217 sampling points obtained during the second national soil survey and the data of 2382 sampling points collected during 2017-2019, this study analyzed the change characteristics of soil organic carbon content of paddy surface soil in Sichuan Basin of China and explored the relationships between the soil organic carbon change of paddy soil and temperature, precipitation, cropland use type, fertilization intensity, and grain yield. The results showed that the content of soil organic carbon of paddy soil changed from 13.33 g·kg-1to 15.96 g·kg-1, with an increase of 2.63 g·kg-1, suggesting that soils in the Sichuan Basin have acted as a carbon sink over past 40 years. The soil organic carbon increment of paddy soil varied with different geomorphic regions and different secondary basins. The increase in SOC content in paddy soil was positively correlated with annual average temperature; negatively correlated with annual average precipitation; and initially increased and then decreased with annual average fertilizer application, annual average increase rate of fertilizer application, annual average grain yield, and annual average grain yield growth rate. The relationship between the increase in SOC content and the annual average temperature growth rate was different under different farmland utilizations, and the increase in the annual average temperature growth rate had significant effects with the increase in SOC content only on paddy-dryland rotation. These results indicate that the paddy soil organic carbon change in Sichuan Basin was co-affected by various factors, but climate warming was an important factor leading to the paddy soil organic carbon change, and its influence was controlled by the water conditions determined by farmland use.

LandInG 1.0: a toolbox to derive input datasets for terrestrial ecosystem modelling at variable resolutions from heterogeneous sources

Abstract. We present the Land Input Generator (LandInG) version 1.0, a new toolbox for generating input datasets for terrestrial ecosystem models (TEMs) from diverse and partially conflicting data sources. While LandInG 1.0 is applicable to process data for any TEM, it is developed specifically for the open-source dynamic global vegetation, hydrology, and crop growth model LPJmL (Lund–Potsdam–Jena with managed Land). The toolbox documents the sources and processing of data to model inputs and allows for easy changes to the spatial resolution. It is designed to make inconsistencies between different sources of data transparent so that users can make their own decisions on how to resolve these should they not be content with the default assumptions made here. As an example, we use the toolbox to create input datasets at 5 and 30 arcmin spatial resolution covering land, country, and region masks, soil, river networks, freshwater reservoirs, irrigation water distribution networks, crop-specific annual land use, fertilizer, and manure application. We focus on the toolbox describing the data processing rather than only publishing the datasets as users may want to make different choices for reconciling inconsistencies, aggregation, spatial extent, or similar. Also, new data sources or new versions of existing data become available continuously, and the toolbox approach allows for incorporating new data to stay up to date.

Теоретические основы расчёта системы ввода органических удобрений во всасывающие трубопроводы насосных станций при удобрительных поливах сельскохозяйственных культур

Purpose: to substantiate theoretically the calculation of the system for introducing organic fertilizers into the suction pipelines of pumping stations during fertilizing irrigation of agricultural crops. Materials and methods. The foundations of calculating the system of introducing organic fertilizers into the suction pipelines of pumping stations during fertilizing irrigation are developed on the basis of literary sources and authors’ research. If there is a composition of nutrients in the manure of cattle (CM), horse, pig or sheep for the planned harvest of the adopted crop, the one-time and annual application amounts for the most toxic element – nitrogen are calculated. It is indicated that in case of a deficiency of nutrients for phosphorus and potassium, an additional calculation for the mineral fertilizers introduction is carried out. Results. An example of calculating the annual amount of irrigation mixture for corn for silage when removing nutrients with an accepted harvest of green mass of 500 q/ha is provided. The calculation is determined by: application rate, cubic meters/ha; nitrogen content in the application rate, kg/ha; the annual volume of the irrigation mixture, with a nitrogen content of 0.15 %. In the example, the calculation is performed for the possible presence of fertilizers in cattle drains according to two variants of technological schemes: without using a mixer, when introducing fertilizers from the storage tank directly into the suction pipeline; using a mixer, when introducing fertilizers from the storage tank into the suction pipe of the mixer. For the calculation, the initial data of hydraulic parameters are given, the consumption of cattle manure with a humidity of 92–95 % is taken as the main calculation parameter. Conclusions: the developed theoretical calculation of the system for introducing organic fertilizers into the suction pipelines of pumping stations allows determining the rate of one-time and annual fertilizer application and determining the hydraulic parameters of the fertilizer input system without a jet mixer.

Conserving fertilizer in China's rural-agricultural development: The reversal shifts and the county-specific EKC evidence from Hubei

This paper examines China's fertilizer conservation in 1978–2017. The provincial data displays a positive reversal shift consistent to the Environmental Kuznets Curve (EKC) hypothesis in fertilizer application. The occurrences of applying less fertilizer but achieving higher farming output, is a positive signal for fertilizer conservation. Then we select Hubei as a case study for more county-specific examinations. To examine Hubei's 80 county-level areas in 2000–2017, we define an ecological impact index of fertilizer use as the local fertilizer application divided by the agricultural gross product. After passing the unit root tests, the panel regressions indicate the N-shaped EKC shift: Hubei's annual county-specific fertilizer-impact indexes rose first with the rural household income, and then declined before they started increasing again, while time effect also existed significantly in the samples. We advise local agricultural policy implementers keep multi-scalar measures and circular economy to conserve fertilizer-use, with more stakeholders engaging fertilizer conservation in rural areas. • We examine the provincial shifts of China's annual chemical fertilizer applications in 1978–2017. • The provincial figures indicate positive signs of farming conservation across provinces in various stages. • The panel regressions of the county-specific data of Hubei in 2000–2017 indicate the N-Shaped EKC. • Hubei's county-specific fertilizer figures rose first, then declined, and rose again, with rural household income. • Policy makers should realize that the rural income growth alone cannot maintain conserving fertilizer and multi-scalar policy implementation and more local engagement help sustain long-term fertilizer ​conservation.

Assessing the nitrate vulnerability of shallow aquifers under Mediterranean climate conditions

The EU Nitrates Directive calls for urgent integration of process-oriented indicators of nitrate fate with map overlay approaches for assessing nitrate vulnerable zones (NVZs). In the region of Campania (southern Italy), groundwater contamination represents a serious concern because of the presence of intensive agricultural practices and livestock farming. A protocol was proposed to assess the probability distribution of the following three indicators of nitrate transport across the vadose zone: i) annual cumulative nitrate flux entering the shallow aquifer, ii) annual cumulative root nitrate uptake, and iii) nitrate transit time across the vadose zone. This method involves numerical simulations of soil water flow and solute transport using Hydrus-1D for a representative 10-m-thick soil profile beneath an irrigated maize plot located in a study area within the Sele plain, Campania. Two scenarios are built by running a set of one hundred (20-yr-long) simulations at a daily time resolution: i) 195 kg N ha-1 of nitrate fertilizer (urea) is applied annually to estimate the probability distributions of annual cumulative nitrate leaching and root nitrate uptake (Scenario 1), ii) 195 kg N ha-1 of nitrate fertilizer (urea) is applied once to estimate the nitrate transit time distribution across the soil profile (Scenario 2). In each Scenario, the simulations consider two agricultural practices with either one or three annual nitrate fertilizer applications subject to randomly generated climate forcing using a Monte Carlo approach. Variations in soil and rainfall properties are described by the Miller-Miller geometric similitude and the Poisson parameterization, respectively.In Scenario 1, roots absorb on average 80.3 kg N ha-1 every year (corresponding to 40% of applied nitrate), and the median annual cumulative nitrate flux across the soil profile bottom is 74.9 kg N ha-1 (representing about 38% of applied nitrate) when urea is applied in a single treatment. In contrast, when fertilizer is applied in three treatments, 112.4 kg N ha-1 (corresponding to almost 60% of applied nitrate) of nitrate is removed by root water uptake, and the median annual cumulative nitrate leaching is 52.4 kg N ha-1 (corresponding to about 27% of applied nitrate). In Scenario 2, mean transit time values are 2741 days, 2707 days, and 2650 days when urea is applied on April 1st, June 1st, and August 1st, respectively. Our model simulations provide useful indicators of nitrate transport and can be integrated with map overlay procedures for delineating nitrate vulnerable zones.

Forage production and steer performance in fertilized smooth bromegrass and smooth bromegrass–legume pastures

AbstractSmooth bromegrass is a commonly used cool‐season pasture grass that responds favorably to annual spring fertilization, but annual fertilizer applications require annual inputs of both time and expense. This study was conducted to determine if interseeding legumes into established smooth bromegrass pasture is a viable alternative to spring fertilization. Steers (Bos taurus) were rotationally grazed in either fertilized smooth bromegrass pastures or smooth bromegrass pastures interseeded with legumes. Data were collected on forage production, forage available at the beginning of each grazing rotation, steer weight gain, and the number of grazing days. Total forage production for the growing season was not different between the pasture types, but fertilized pasture had greater available forage early in the growing season and interseeded pasture had greater forage production late in the growing season. Season‐long average daily gain of steers was not different between pasture types, but daily gains were greater in interseeded pasture late in the growing season and may be linked to proportionally greater abundance of legumes late in the season. Beef production ac–1 was higher in interseeded pastures, largely due to increased days of grazing. We found that interseeding legumes into established pasture can be a viable alternative to annual spring fertilization and may outperform fertilized pasture depending on the metric and growing conditions.

Nutrients Leaching in Response to Long-Term Fertigation and Broadcast Nitrogen in Blueberry Production.

Nutrient leaching losses from horticultural production threaten the quality of groundwater and freshwater systems worldwide. The objectives of this study were to (a) assess the effects of annual applications of ammonium sulfate fertilizer through fertigation (FERT) and broadcast (BROAD) on nutrient leaching losses and (b) determine the links among chemical property changes in leachates and soil with berry yields after 9 and 11 years of blueberry production. The long-term blueberry site was established in 2008 using seven combinations of treatments including an unfertilized control (CONT) and three N fertilizer rates (100%, 150%, 200% of recommended rates) using BROAD and FERT methods. Nutrients concentrations (NO3−-N, NH4+-N and SO42−-S) and chemical properties (pH and electrical conductivity (EC)) of leachate, sawdust and soil and berries were assessed. All FERT methods resulted in concentrations of NO3−-N in the leachates > 100 mg L−1 with a maximum of 200 mg L−1 for FERT-200 during the growing season due to the easy transport of dissolved nutrients with the irrigation water. All BROAD methods resulted into concentrations of NO3−-N in the leachates >10 mg L−1 with a maximum of 35 mg L−1 for BROAD-200 between April and July, as well as between November and April, indicating two periods of NO3−-N leaching losses. The pattern observed with BROAD indicates that irrigation water in the summer and heavy rainfall in the winter contribute to NO3−-N leaching losses. Concentrations of NH4+-N in the leachates >1 mg L−1 were measured under FERT with a peak at 64.78 mg L−1 for FERT-200, during the period April to August, due to NH4+’s ability to quickly move through the sawdust layer with irrigation water. Principal component analysis linked berry yield decrease with ammonium sulfate applications above recommended rates (FERT and BROAD) and with changes in soil pH and EC. Our results demonstrated that excess fertilizer applications above recommended rates using FERT and BROAD can threaten the sustainability of blueberry production by enhancing nutrient leaching losses and reducing berry yield.

Changes in soil physical and chemical characteristics in intensively cultivated greenhouse vegetable fields in North China

The total area of greenhouse crop production is increasing in China. However, this adversely influences soil physical and chemical properties due to special environmental conditions and agricultural management in greenhouse production. In this study, we evaluated soil properties of greenhouse vegetable systems with different planting years, a long-term greenhouse strawberry system, and an open-field wheat-maize rotation system in a typical agricultural production area of North China. The annual fertilizer application rates of nitrogen (N), phosphorus (P), and potassium (K) in the greenhouse vegetable system were 842.15, 809.14, and 931.55 kg ha−1, respectively, which were 3 times more than those in the wheat-maize rotation system and led to great changes of soil properties. Bulk density and soil pH gradually declined with increased cultivation time from new to 15 years in the greenhouse vegetable system. Bulk density declined from 1.58 g/cm3 in the new greenhouse fields to 1.25 g/cm3 in the 15-year greenhouse fields, and pH decreased from 5.72 to 4.55 with a rate of 0.08 unit per year. The contents of soil organic carbon (SOC), soil soluble salts, total NPK, and available NPK rose steadily until the 10th or 11th year, then decreased. By comparison with another two cropping systems, the greenhouse vegetable fields showed the lowest bulk density and pH, but the highest contents of SOC, soil soluble salts, total NPK, and available NPK due to heavy fertilizer inputs. The contents of soil N, P, and K in greenhouse vegetable fields were imbalanced, as indicated by C:N (11.58), C:P (16.06), and N:P (1.71) molar ratios in soils, which were significantly lower than the level in China and the rest of the world. In addition, the C:P and N:P ratios of greenhouse vegetable fields were also lower than those of wheat-maize rotation fields and greenhouse strawberry fields. Regression analysis indicated that the contents of SOC and soluble salts were positively correlated with pH, while available N and P contents showed negative linear relationships. These results demonstrate dramatic adverse changes of soil properties in intensive greenhouse vegetable fields in China. Our results also emphasize the need to regulate appropriate fertilizer application for intensive greenhouse vegetable management.

What has caused the use of fertilizers to skyrocket in China?

The consumption of fertilizers in China has skyrocketed in the last six decades and this raises strong environmental concerns. The study was conducted to determine which crop production factors have contributed to the increased use of fertilizers in China. Firstly, annual fertilizer application data for 16 major crops over the period 1950–2010 were estimated, and periodic changes were analyzed to determine the contributions made by total cropping area (TCA), fertilizer application rate (kg ha−1, FAR), and crop type (proportions of TCA for individual crops, CT). Results show that total fertilizer consumption increased from 0.07 Mt in 1950 to 49.6 Mt in 2000, and 74.7% of the increase is attributable to FAR, 0.05% to TCA, and 25.3% to CT. The contribution of FAR to total fertilizer consumption decreased (from 98.3% in the 1950s to 65.6% in the 2000s), while the contributions of TCA and CT increased (from 0.90 and 0.81% in the 1950s to 17.5 and 16.8% in the 2000s, respectively). Maize, rice, and wheat were the major crops to which most of the fertilizers (up to 87.9%) were applied before the 1980s. However, after the 1980s maize, vegetables and fruits became the major drivers of fertilizers consumption. These three crops contributed 59.6% in the 1990s and 90.6% in the 2000s to the increased consumption of fertilizers. Results suggest that shifts in FAR and CT may be the critical control points for future fertilizer consumption, and increased integrated soil-crop system management in China should focus on vegetables and fruits.

Phosphate and glyphosate sorption in soils following long-term phosphate applications

Phosphate and glyphosate molecules compete for sorption sites in soil. The objective of this study was to quantify the impact of Olsen P concentrations in two contrasting soils on phosphate and glyphosate sorption. Soils were a sandy clay loam soil rich in iron oxides (SCL-Fe2O3) and a clay loam soil rich in calcium carbonates (CL-CaCO3). The phosphate Freundlich sorption coefficient (Kf) ranged from 3 to 68L1/nmg1–1/nkg−1 in the SCL-Fe2O3 and from 21 to 76L1/nmg1–1/nkg−1 in the CL-CaCO3. Glyphosate sorption coefficient (Kd) ranged from 293 to 1173Lkg−1 in the SCL-Fe2O3 but only 99 to 141Lkg−1 in the CL-CaCO3. Glyphosate Kd and phosphate Kf values decreased significantly with increasing Olsen P concentrations in both soils. Glyphosate Kd values were further significantly reduced when phosphate was added to the slurry solutions, but phosphate Kf values were not impacted by the presence of glyphosate in solutions. We conclude that annual phosphate fertilizer applications leave phosphate concentrations in Prairie soils to the extent that soils have a lesser capacity to retain glyphosate and phosphate that are subsequently applied, but glyphosate residues will not influence phosphate sorption.

The effect of 72 years of sugarcane residues and fertilizer management on soil physico-chemical properties

This study, carried-out in KwaZulu-Natal, South Africa, investigated changes in selected soil properties and their effect on aggregation induced by 72 years of residue burning or mulching, with and without fertilizer application on a sugarcane trial arranged in a split-plot design with four replications. The main plot treatments were a) green cane harvesting with all residues mulched, b) cane burnt prior to harvest with cane-tops left scattered evenly over the plots and c) cane burnt prior to harvest with all the residues removed from the plots. Split-plot treatments consisted of fertilized and unfertilized plots. Soil samples for physico-chemical and aggregate stability analysis were collected at depths of 0–10 and 10–20cm from 24 plots. In comparison with burning, significant effects of mulching were only observed on total nitrogen and exchangeable potassium and sodium, mainly at 0–10cm. Aggregate stability estimated by mean weight diameter (MWD), exchangeable cations (especially calcium and magnesium) and pH were significantly affected by fertilizer application. An increase in acidity and a decrease in MWD and exchangeable calcium and magnesium on fertilized plots were attributed to mining of nutrients by sugarcane, nitrification and subsequent base cation leaching. The significant positive correlation between calcium and magnesium and MWD, and the lack of correlation between organic carbon (OC) and MWD, indicated that bases contributed more to soil aggregation than OC. Total carbon and OC showed no differences across all treatments. It was concluded that (i) annual fertilizer applications may lead to soil structure deterioration under sugarcane regardless of the harvesting method practiced and (ii) increasing additions of organic matter (through mulching) do not always correspond to an improvement of soil aggregate stability and related soil properties.

Nitrogen Fertilization Effects on Productivity and Nitrogen Loss in Three Grass-Based Perennial Bioenergy Cropping Systems.

Nitrogen (N) fertilization can greatly improve plant productivity but needs to be carefully managed to avoid harmful environmental impacts. Nutrient management guidelines aimed at reducing harmful forms of N loss such as nitrous oxide (N2O) emissions and nitrate (NO3-) leaching have been tailored for many cropping systems. The developing bioenergy industry is likely to make use of novel cropping systems, such as polycultures of perennial species, for which we have limited nutrient management experience. We studied how a switchgrass (Panicum virgatum) monoculture, a 5-species native grass mixture and an 18-species restored prairie responded to annual fertilizer applications of 56 kg N ha-1 in a field-scale agronomic trial in south-central Wisconsin over a 2-year period. We observed greater fertilizer-induced N2O emissions and sub-rooting zone NO3- concentrations in the switchgrass monoculture than in either polyculture. Fertilization increased aboveground net primary productivity in the polycultures, but not in the switchgrass monoculture. Switchgrass was generally more productive, while the two polycultures did not differ from each other in productivity or N loss. Our results highlight differences between polycultures and a switchgrass monoculture in responding to N fertilization.

ORGANIC CARBON CONTENTS AND STOCKS IN PARTICLE SIZE FRACTIONS OF A TYPIC HAPLUDOX FERTILIZED WITH PIG SLURRY AND SOLUBLE FERTILIZER

The use of pig slurry (PS) as fertilizer can affect the soil quality and increase total stocks of soil organic carbon (TOC). However, the effects of PS on TOC amount and forms in the soil are not fully understood, particularly in areas under no-tillage (NT). The purpose of this study was to determine TOC contents and stocks in the particulate (POC) and mineral-associated C fractions (MAC) of an Oxisol after nine years of maize-oat rotation under NT, with annual applications of PS, soluble fertilizer and combined fertilization (pig slurry + soluble fertilizer). The experiment was initiated in 2001 in Campos Novos, Santa Catarina, with the following treatments: PS at rates of 0 (without fertilization - PS0); 25 (PS25); 50 (PS50); 100 (PS100); and 200 m3 ha-1yr-1 (PS200); fertilization with soluble fertilizer (SF); and mixed fertilization (PS + SF). The TOC content was determined in samples of six soil layers to a depth of 40 cm, and the POC and MAC contents in four layers to a depth of 20 cm. From the rate of 50 m3 ha-1yr-1 and upwards, the soil TOC content and stock increased according to the PS rates in the layers to a depth of 10 cm. The POC and MAC contents and stocks were higher in the surface layers, with a clear predominance of the second fraction, but a greater relative amplitude in the contents of the first fraction.

Pine straw raking and fertilizer source impacts on nitrogen mineralization in a loblolly pine plantation

Pine straw production can supplement traditional revenues generated by loblolly pine plantation management. However, there is concern that excessive straw removal may adversely affect nitrogen availability and thus straw and fiber productivity in these stands. This study evaluated the long-term effects of straw raking combined with or without supplemental applications of either commercial inorganic fertilizer or poultry litter on soil N and C dynamics in a loblolly pine plantation in north central Louisiana. In situ mineralization and nitrification were measured monthly in response to: (1) no raking or fertilizer, (2) annual straw raking for seven years, (3) annual straw raking for seven years with inorganic fertilizer application for five years, and (4) annual straw raking for seven years with annual poultry litter application for five years. Annual straw raking did not substantially alter the N and C pools observed in this study. Annual applications of inorganic fertilizer did not lead to an accumulation of N in the uppermost 15cm of mineral soil. Annual applications of poultry litter in conjunction with straw raking increased total C, total N, and exchangeable N (particularly as NO3–N), N mineralization, and nitrification in soil. Due to the greater propensity of poultry litter to increase NO3–N in soil relative to inorganic fertilizer, applying poultry litter at the frequency, rate, and/or target N rate used for inorganic fertilizer may have led to application of N in excess of plantation N demand at this site.

Assessment of the Contribution of N-Fertilizers to Nitrate Pollution of Groundwater in Western Iran (Case Study: Ghorveh–Dehgelan Aquifer)

Nitrate pollution of groundwater resources has increasingly become a global concern. Groundwater from the Ghorveh-Dehgelan aquifer serves as the main source of water supply for drinking and irrigation within the province of Kurdistan (western Iran). This study investigated (1) groundwater nitrate status as well as the pollution sources and (2) the spatial extent of groundwater nitrate pollution in the region. A total of 72 and 93 samples of groundwater were taken for measurement of nitrate concentration during 2008 and 2013, respectively. Our results showed that 12 wells (12.9 %) exceeded the World Health Organization’s acceptable threshold (50 mg L $$^{-1})$$ in 2013. The detailed analysis of spatial distribution of the polluted wells revealed that all are located within areas of irrigated agriculture. In addition, our further investigation of annual fertilizer application and the spatial distribution of polluted wells revealed that input of artificial nitrogen fertilizers to irrigated lands was strongly correlated to nitrate concentration within groundwater in these areas. Moreover, the transportation of nitrate through the aquifer has been mainly controlled by geology and pattern of groundwater flow, and therefore, groundwater flow should be taken into account for future quality management of the aquifer. The results of this study will provide useful guidelines for utilizing of nitrate fertilizers in regards to groundwater quality to avoid repeating the problem of groundwater nitrate pollution.

On-farm assessment of soil erosion and non-point source pollution in a rain-fed vegetable production system at Dianchi lake’s catchment, southwestern China

Vegetable is important cash crop in Dianchi lake’s catchment, but the non-point source (NPS) pollution from the intensive agricultural production systems is a critical hurdle on the alleviation of serious eutrophication in Dianchi lake. Our objectives were to quantify soil erosion and NPS pollution in rain-fed vegetable production systems at the area. The experiment was a randomized complete factorial design with two plastic mulch treatments (narrow vs. wide plastic mulch) and two rotation treatments (broccoli–zucchini–winter wheat vs. broccoli–zucchini–fallow). The narrow-plastic-mulch system has significantly (P < 0.05) increased runoff and soil loss than wide-plastic-mulch system. Results indicated that plastic mulch substantially accelerated runoff generation and soil erosion at vegetable seedling stages, whereas runoff and soil loss were apparently alleviated in furrow with residue mulch. The sediment transport played a predominant role in soil nitrogen (N) and phosphorus (P) movement by surface runoff. The annual losses of N and P via surface runoff in the vegetable field were ranged from 2.0 to 5.1 kg/ha and 0.3 to 1.1 kg/ha respectively in the three considerably drier rain season, but their losses never exceeded 1 % of the annual fertilizer application. Removal of crop residues was the major causes of N and P export from the soil in the vegetable fields, which exceeded 20 and 8 % of the annual nitrogen and phosphorus fertilizer application respectively. This implicated that inappropriately discarding of the residues would pose serious consequences for water contamination of Dianchi lake. As under appropriate discarding of residues, the wide-plastic-mulch system could improve NPS pollution control and crop production in vegetable field at Dianchi lake’s catchment.

Season and phosphorus age effects on the relationship between maize yield and phosphorus soil test on a highly weathered soil

This paper discusses data obtained from a long-term N, P, K field experiment with maize (Zea mays L.) on a Normandien clay loam (Plinthic Paleudult) near Newcastle, Natal. After eight seasons plots were split, sub-plots being allowed either to rundown or continuing to receive annual P applications. Soil samples were obtained shortly after fertilization each season and P soil tests were related to final grain yield. The results obtained indicate that although yield maxima varied from 3 000 kg ha−1 in the dry 1981/82 season to over 6 500 kg ha−1 in the more favourable 1983/84 season, there was no meaningful difference in the optimum P soil test using either the Ambic, modified Truog or Bray 1 extractants. Furthermore, the relationship between yield and soil test was identical for residual P subplots and those which received annual applications of fertilizer P.

Short‐Term Effects of Mineral and Organic Fertilizer on Denitrifiers, Nitrous Oxide Emissions and Denitrification in Long‐Term Amended Vineyard Soils

Short‐term effects (i.e., 21 d) of mineral or organic fertilizer application on long‐term (i.e., 8 yr of applications) amended soil on denitrifier community abundance, denitrification gene mRNA transcript numbers, denitrification rate, and emissions of N2O were explored. Soil was collected from a vineyard in Italy receiving annual applications of either mineral fertilizer (conventional management system, CS) or municipal compost (organic management system, OS). Each soil was incubated using three treatments: no amendment, NH4NO3, or municipal compost. Microcosms set up with soil treated with compost showed higher nirS, nirK, and nosZ abundance in comparison to conventional fertilization. Short‐term compost addition increased nirK gene abundance over time in OS and CS soils, whereas nirS and nosZ gene abundance increased after compost addition only in OS soil. In OS soil, nosZ gene mRNA transcript numbers were higher at all time‐points for all treatments compared with CS soil. Furthermore, nosZ gene mRNA transcript number increased over time after compost addition for both soils, N2O emissions were higher in both soils after NH4NO3 addition compared with no amendment and compost addition. Denitrification was higher in OS than CS soil following NH4NO3 treatment. Denitrification rates were much higher than N2O rates in all cases suggesting most emissions occurred as N2. Our study demonstrated that long‐term urban‐waste compost application clearly changed soil denitrifier communities and the response of denitrification and N2O emissions to different short‐term soil amendments.

Soil Accumulation of Nitrogen and Phosphorus Following Annual Fertilization of Loblolly Pine and Sweetgum on Sandy Sites

A key question that arises following fertilization of forest plantations in the southeastern United States is whether fertilization has a long‐term effect on nutrient availability and long‐term site quality. Site quality could improve if mineral soil N and P pools are increased but is less likely if only forest floor pools are increased. Rapid forest floor decomposition and nutrient release following harvest likely lead to only rotation‐length increases in nutrient availability. To examine the impact of repeated applications of N and P, forest floor and mineral soil N and P pools were measured at a 24‐yr‐old loblolly pine (Pinus taedaL.) plantation in North Carolina (Southeast Tree Research and Education Site [SETRES]) and 13‐yr‐old loblolly pine and sweetgum (Liquidambar styracifluaL.) plantations in Georgia (Mt. Pleasant) receiving annual incremental fertilizer applications totaling &gt;1000 kg N ha−1and &gt;160 kg P ha−1. Mineral soil N pools varied only slightly. In contrast, fertilization increased forest floor N pools by 300 kg N ha−1at SETRES. Long‐term impacts on site N availability and site quality following these large N applications are unlikely. The forest floor P pool at SETRES was increased by 19.8 kg P ha−1. Fertilization also increased the mineral soil extractable P pool at SETRES to a depth of 1.5 m by 56 kg P ha−1but not at Mt. Pleasant where P fertilization during the previous rotation may have already increased this pool. Observed increases in mineral soil P from fertilization indicated a potential for increased long‐term site quality in terms of higher P availability for future rotations.