Unfertilized Treatment Research Articles

Decrease in soil test phosphorus levels under omitted phosphorus fertilizer application

AbstractMany European cropped soils have high soil test P (STP) values in the top soil because of P accumulation over many years of fertilizer application. This should allow to save P fertilizer applications for some years without STP values decreasing to a level that might negatively impact crop yield. However, the way STP develops under omitted P fertilizer application is not well understood. We examined STP development under omitted P fertilizer application for timeframes between 7 and 46 years on 96 unfertilized treatments (P0 treatments) of 43 European long‐term P field experiments, using five different STP methods. For comparability, values obtained by different STP methods were converted to Olsen‐P concentrations. We fitted exponential decay curves to Olsen‐P data of each P0 treatment defined by initial Olsen‐P values (Olsen‐Pi), rates of decrease (k) and asymptotes (A), reflecting minimum obtainable STP. Subsequently, we analysed whether the variables most commonly recorded in experiments, are sufficient to explain the variation in model parameters, these variables being P export, clay content, Corg and pH as well as average annual temperature and precipitation. We found that out of our predictor variables, soil clay content, precipitation and temperature were showing the most prominent effects on the parameters Olsen‐Pi, A or k. However, the amount of variation explained by the considered variables was too low to potentially facilitate a prediction of STP decrease, and various P0 treatments showed no clear Olsen‐P decrease or unexpectedly high asymptotes. This hints at a strong influence of the P sorption capacity of the soil with often high potential for replenishment from less available P pools. In connection with P introduction from the subsoil or possibly from surrounding plots, the extension of timeframes of omitted P fertilizer application without reaching critical STP values for crop production, might be explainable. Corresponding effects could not be analysed because of lack of data for most P0 treatments, calling for the additional determination of, for example, the maximum P sorption capacity, total P and subsoil P in future experiments.

Soil nitrogen and phosphorus regulate decomposition of organic nitrogen compounds in the rothamsted experiment

The effects of long-term N and P fertilisation on soil organic nitrogen (SON) turnover are unclear. We sampled soils fertilised by N and/or P since 1843 at Rothamsted Research to investigate the effects of long-term N and P fertilisation on high- or low-molecular-weight SON decomposition and gross N mineralisation. Short-term assays with added 14C-labelled proteins, peptides, and amino acids and gross organic N mineralisation were measured, and the microbial communities and functions were also assessed in parallel. Long-term N fertilisation increased the contents of soil extractable organic N and peptides but decreased organic N-hydrolysing enzyme activities (N-acetyl-β-D-glucosaminidase and leucine aminopeptidase). Fertilisation with P and N accelerated and reduced the decomposition of 14C-labelled organic N compounds, respectively. The decomposition of peptides and amino acids, as labile SON components, was mainly regulated by soil P content because microbial biomass and activity were more sensitive to P fertilisation than to N fertilisation. Gross NH4+/NO3− production and consumption were accelerated by 41%–60% under N fertilisation but remained unchanged under P fertilisation compared to the unfertilised treatment. Metagenomic sequencing showed that N fertilisation increased microbial diversity and enriched functional genes associated with organic N decomposition, compared to the unfertilised treatment. P fertilisation had no effect on the abundance of these functional genes. In agricultural practices, it is essential to comprehensively consider the interaction between N and P fertilisation to optimise the cycling and utilisation of SON.

Effects of Straw Addition on N2O and CO2 Emissions from Red Soil Subjected to Different Long-Term Fertilization

Straw return, as an important measure for soil fertility improvement in farmland, significantly affects the emissions of greenhouse gases N2O and CO2. Thus, the collected soil samples from five long-term (30-year) fertilization treatments (no fertilization, CK; recommended chemical fertilizer, F; 200 % of recommended chemical fertilizer, 2F; pig manure, M; and chemical fertilizer combined with pig manure, FM) were amended with and without straw and incubated under constant temperature and humidity conditions (25 ℃ and 65 % maximum field water holding capacity) for 20 days so as to investigate the key factors influencing N2O and CO2 emissions in response to straw addition in long-term fertilization treatments. The results showed that fertilization significantly increased N2O emissions. Compared to those under the unfertilized treatment[(22.05 ±2.09) μg·kg-1, calculated as nitrogen, the same as below], cumulative N2O emissions from the chemical fertilizer treatments significantly increased by 119 %-195 %[(48.38 ±20.81) μg·kg-1 and (65.13 ±12.55) μg·kg-1 from the F and 2F treatments, respectively], and those from the manure treatments increased by 275 %-399 %[(82.72 ±12.73) μg·kg-1 and (1 101.99 ±425.71) μg·kg-1 from the M and FM treatments, respectively]. Soil NO3--N, DOC, and DTN were the main factors influencing N2O emissions from fertilized treatments in the absence of straw addition. Straw addition significantly increased cumulative N2O emissions by 345 % and 247 % in the 2F and M treatments, respectively, compared to those in the corresponding fertilized treatments without straw addition, with no significant effect on N2O emissions in the CK, F, and FM treatments. Straw addition increased DOC content and microbial activity and decreased soil NO3--N and DTN contents, thereby increasing N2O emissions. Fertilization also significantly increased CO2 emissions. Compared to those from the unfertilized treatment, cumulative CO2 emissions from the manure treatments significantly increased by 120 %-130 %[(122.11 ±4.3) mg·kg-1 (calculated as carbon, the same as below) and (116.47 ±4.55) mg·kg-1 from the M and FM treatments, respectively], and those in the 2F treatment increased by 28 %[(65.13 ±12.55) mg·kg-1]. In the absence of straw addition, soil MBC, DOC, and DTN were the main factors influencing CO2 emissions. Compared to those in the treatments without straw addition, straw addition significantly increased cumulative CO2 emissions by 660 %-1132 % among fertilization treatments, due to increased DOC and MBC contents and enhanced microbial activity. In conclusion, straw addition significantly increased N2O and CO2 emissions through increased soil DTN consumption and DOC content among fertilization treatments. In soils treated with manure amendment, straw return should be rationally considered for the purpose of balancing the comprehensive trade-offs between fertility improvement and greenhouse gas emissions.

Utility of in situ ion‐exchange membranes to assess nutrient availability, productivity, and fertilizer response of coastal Douglas‐fir of the Pacific Northwest

AbstractDouglas‐fir [Pseudotsuga menziesii (Mirb.) Franco] is the predominant forest plantation species in the Pacific Northwest (PNW), with site productivity and fertilizer response influenced by climate and soil variations. This study investigates the utility of in situ 12‐week supply measurements of nitrogen (N), calcium (Ca), and phosphorus (P) to ion‐exchange resins (specifically Plant Root Simulator [PRS] probes) to estimate carbon (C):N ratios, soil nutrient contents (0–1 m), foliar nutrient concentrations, Douglas‐fir productivity (site index and basal area mean annual increment), and fertilizer volume response. PRS nutrient supply rates were correlated with N, Ca, and P soil nutrient contents (0–1 m), C:N ratios, and foliar nutrient concentrations. Low PRS NO3 supply rates (<25 mg N·m−2·burial period−1) were correlated with lower Douglas‐fir productivity and greater fertilizer volume response. PRS NO3 supply rates performed as well as total soil N contents and foliar N concentrations at estimating volume growth response to fertilizer. Twelve weeks after fertilization, PRS NO3, NH4, and Ca supply rates were significantly elevated compared to the unfertilized treatment. This research found that PRS probes were an effective in situ tool and are recommended for understanding N, Ca, and P nutrient availabilities, site productivity, and fertilizer response in Douglas‐fir plantations and for developing fertilizer prescriptions.

Bottom-up population regulation of Orthotomicus erosus on irrigated and fertilized Pinus eldarica: A comprehensive field study

The Mediterranean pine engraver, Orthotomicus erosus (Wollaston), is a destructive pest that has caused a significant threat to planted pine forests worldwide through feeding on phloem, disrupting sap flow and transmitting phytopathogens. This study investigated the bottom-up effects of different irrigation and fertilization treatments on the mean numbers of O. erosus immature stages (egg, larva and pupa) and adults in the pine forest of western Tehran, Iran. A total of 72 Pinus eldarica Medw. trees were selected in Chitgar Forest Park. The experiment was arranged as a split plot in a randomized complete block design with three replications. The irrigation treatments included non-irrigation, low-irrigation (30 liters of water per month) and high-irrigation (30 liters of water per two weeks) were assigned to main plots. Moreover, fertilizers of nitrogen 100 kg/ha, superphosphate 100 kg/ha and potassium sulfate 65 kg/ha were applied in subplots. Then, the total number of O. erosus life stages was counted under the bark samples (two 10 × 10 cm bark samples) separated from the pine trees. Results showed that irrigation and fertilization significantly affected the mean number of O. erosus from egg to adult stages. Irrigation had a more pronounced effect on the pest population than fertilization. The highest number of different life stages occurred in non-irrigated pines regardless of fertilization. Moreover, fertilizer effects were influenced by irrigation, where high irrigation negatively affected superphosphate + potassium sulfate fertilized pines and significantly increased the mean numbers of different O. erosus life stages compared to low-irrigation treatment. The lowest mean number of egg (11.95 ± 0.17), larva (8.62 ± 0.21), pupa (10.38 ± 0.13) and adult (9.04 ± 0.23) per bark samples occurred in superphosphate + potassium sulfate at low-irrigation plots. Interestingly, nitrogen fertilization increased pest density compared to unfertilized trees. Furthermore, despite the low mean number of different O. erosus life stages in superphosphate + potassium sulfate treatments, the nitrogen combination increased the pest density in both low and high-irrigation plots. These findings highlighted the importance of considering the interaction between irrigation and fertilizer types in the integrated pest management program for O. erosus.

Increasing mowing height and nitrogen fertility does not enhance unirrigated centipedegrass summer drought stress

AbstractProper N fertilization and higher mowing heights are recommended to enhance rooting for greater turfgrass summer drought stress. To examine the effects of these primary cultural practices on centipedegrass [Eremochloa ophiuroides (Munro) Hack.] drought response in the mid‐Southern United States, a study was conducted to evaluate four mowing heights (1, 2, 3 and 4 inches) and N fertilization versus no fertilization. During the study, roots were periodically harvested at upper (0–3 inches) and lower (3–6 inches) soil depths, and roots were analyzed for architecture which included root length (RL) and surface area (SA), and root weight (RW). In July, plant‐soil cores were subjected to 36‐day drought simulation under greenhouse conditions. All turfgrass exhibited a pattern of decreasing leaf quality as drought progressed with unfertilized treatments maintaining acceptable leaf color (≥5) for 19 days at 5.9 compared to 4.8 for fertilized centipedegrass regardless of mowing height. In the field, root architecture and biomass across all mowing heights, fertilities, and soil depths peaked at 883.9 inches, 35.6 in2, and 5.8 grains for RL, SA, and RW, respectively, six weeks prior to drought simulation (WDPS) before declining to 740.5 inches, 29.6 in2, and 4.9 grains at the initiation of the drought simulation. The inability of N fertility and mowing height to enhance root growth particularly from spring into summer indicates soil temperatures may be a factor in centipedegrass root growth and thus drought stress avoidance.

Enhancing the Yield of Mature Olive Trees via Comparative Fertilization Strategies, including a Foliar Application with Fulvic and Humic Acids, in Non-Irrigated Orchards with Calcareous and Non-Calcareous Soils

This study investigated the impact of fertilization treatments on mature, forty-year-old, fully productive olive trees (Olea europaea L. cv. Koroneiki) in two non-irrigated orchards featuring contrasting soil types: non-calcareous–acidic and calcareous–alkaline. Over three years (2019–2021), seven distinct treatments were applied, involving inorganic soil fertilizers (traditional strategy) and foliar applications of a liquid organic product containing fulvic and humic acids. Fertilization significantly influenced physiological parameters, such as mineral nutrition, photosynthetic pigments of olive leaves, fruit yield, and oil production per tree, revealing noteworthy effects influenced by soil types and their interactions with treatments. Statistical analysis highlighted specific treatments, indicating that the foliar application of the organic product once a year in alkaline soil or biannually in acidic soil resulted in the highest observed fruit yield and oil production per tree. Indeed, contrary to the control–unfertilized trees, specific fertilization strategies resulted in an average increase of up to 47% and 73% in fruit yield per tree and up to 96% and 100% in oil production per tree in acidic and alkaline soil, respectively. Furthermore, consistently high yields were correlated with constant high values of the chlorophyll a/chlorophyll b ratio (2.3–3.3 in August for acidic soil) and leaf chlorophyll a concentration (55–66 mg/100 g f.w. in August for alkaline soil). This novel finding underscores the crucial role of these factors as prerequisites for achieving superior fruit production. Our results emphasize the potential of integrating foliar organic fertilization as a complementary strategy to traditional soil-based approaches. This is particularly relevant under non-irrigated/rainfed cultural conditions, emphasizing the significance of considering alternative fertilization practices for optimized olive orchard management.

Importance of Overlooked Crop Biomass Components in Sugarcane Nitrogen Nutrition Studies

Sugarcane crops typically have a high fertiliser nitrogen (N) input, with low N recovery efficiencies. Nitrogen is essential to crop productivity, but excess application can have negative environmental consequences. Despite the importance of coordinating N fertiliser input with crop N requirements, certain components of the sugarcane plant are typically not considered when evaluating N nutrition. The objective of this study was to establish which sugarcane crop components should be included in these evaluations given their impact on N mass accumulation and on fertiliser N recovery efficiencies. The respective biomass, N mass, and fertiliser N recovery efficiency were evaluated for sugarcane shoots, tillers, strawfall, root, and stool components over two experimental years, for fertilised (urea) and unfertilised treatments. The root component comprised, respectively, 57–65% of the aboveground N mass of fertilised sugarcane, and 74–104% of the unfertilised sugarcane. The sugarcane N requirements and uptake were shown to be more progressive over the growth-cycle when considering the strawfall and tiller components. This study emphasises the importance of evaluating belowground biomass in sugarcane N studies, and suggests that the tiller and strawfall components should also be considered when evaluating the evolution of N mass and fertiliser N recovery efficiency.

Dual‐purpose cowpea grain and fodder yield response to variety, nitrogen–phosphorus–potassium fertilizer, and environment

AbstractAddressing the challenges of food and nutrition insecurity in sub‐Saharan Africa will require innovative agriculture production systems that support multiple objectives. Dual‐purpose cowpea [Vigna unguiculata (L) Walp] varieties are expected to offer greater grain yields for human consumption and high‐quality fodder for livestock in semiarid regions of Senegal. However, limited information is available on the effects of varieties and fertilizer on dual‐purpose cowpea. The main objective of this research was to evaluate the grain and fodder yield of five newly released cowpea varieties (Kelle, Leona, Lizard, Sam, and Thieye) compared to traditional variety (Yacine) with fertilizer (nitrogen‐phosphorus‐potassium 6‐20‐10) and no‐fertilizer application. Genotype × environment × management experimentations were conducted across three cowpea production zones of Darou Mousty (400 mm per year), Bambey (500 mm per year), and Boulel (700 mm per year) over three growing seasons (2019–2021) to compare the growth and yield parameters of the cowpea varieties. Results of the study showed a 40% grain yield advantage from the greater yielding (Leona) variety in this study compared with the lower yielding (Lizard) variety. There was an additional 22% grain yield increase from the application of fertilizer compared with the unfertilized treatment. The variety (Leona) that produced the most grain also produced the most fodder yields. There was 67% fodder yield advantage from Leona compared with fodder yield from the older variety Yacine. Across varieties, application of fertilizer increased fodder yield by 15% compared to the unfertilized control. Average grain yield in high‐yielding environment (Boulel 2019, Darou Mousty 2019, and Bambey 2021) was 100% greater compared with average grain yield in low‐yielding environments (Boulel 2021, Darou Mousty 2021, and Bambey 2019). Compared to Yacine, dual‐purpose varieties increased net returns by 15%–58% or 13%–42% with early‐ and late‐season cowpea sales, respectively. However, fertilizer application was profitable only when cowpea grain and fodder were sold later in the season. In general, cowpea number of branches, pod number, and pod yield increased with fertilizer application. We concluded that producers can adopt dual‐purpose varieties and proper fertilizer management to increase grain yield, fodder availability, and profitability of cowpea production in Senegal.

Anaerobic digestates from cow dung and food waste as fertilizers: Effect on tomato growth and yield

Organic farming systems aim to reduce chemical inputs including fertilizers and ensure sustainable and eco-friendly production while recycling local renewable resources such as organic wastes. The aim of this study is to investigate the effect of two anaerobic digestates on tomato yield and growth in open field conditions. Digestates consisting of cattle dung and food waste from a 15 m3 demountable digester and fixed-dome digester, respectively, were applied to tomato cultivation using tree fertilization treatments: 1) raw (PD100) and 2) diluted up to 50% (PD50) cattle dung digestate, 3) food waste digestate (DD), and an unfertilized treatment (control) for 21 weeks. The results showed that tomato plants fertilized with PD50 and DD were significantly higher (+34% and +33%, respectively) compared to the control and PD100 (p<0.05), and all digestate treatments significantly (p<0.05) enhanced plant elongation compared to the control. This study suggests that anaerobic digestates can be a helpful alternative in the perspective of partial substitution of chemical fertilizers for sustainable tomato production.

Impacts of Long-term Application of Fertilizer and Manures on Physico-chemical Properties, Phosphorus Uptake and Crop Yield at Different Growth Stages of Wheat

A field experiment was conducted on wheat in a sandy loam soil (Typic Haplustept) at IARI farm, New Delhi during 2018-19 in a long-term fertilizer experiment to study the physico-chemical properties of soil, crop yield, phosphorus uptake and phosphorus availability. The experiment was designed with seven different treatments, replicated thrice in a randomized complete block design. The treatments details were T1: Control, T2: 100%N, T3: 100%NP, T4: 100%NPK, T5: 150% NPK, T6: 100%NPK+5t FYM and T7: 100% NPK+ Zn-5 kgha-1. The results revealed that pH and electrical conductivity were highest under control and lowest recorded under 100% NPK+FYM. Available phosphorus content at all four stages was wheat significantly greater under NPK+FYM followed by 150% NPK treatment and lowest under nitrogen alone (100% N) and unfertilized treatment (control). Initially available phosphorus in soil ranged from 13.5 to 39.8 and 15.4 to 37.9 kg ha-1 at 0-15 cm and 15-30 cm depth, respectively. At the tillering stage, available P was 20.7 to 43.7 and 16.5 to 38.1 kg ha-1 at 0-15 cm and 15-30 cm depth, respectively. At panicle emergence, it was 24.1 to 48.4 kg ha-1 and 18.6 to 42.3 at 0-15 cm and 15-30 cm depth. At harvest of wheat crop, available P ranged from 20.5 to 41.8 and 16.5 to 39.1 kg ha-1 at 0-15 cm and 15-30 cm depth, respectively. Total phosphorus uptake and crop yield significantly increased under 150% NPK treatment followed by 100% NPK+FYM.

Higher than expected: Nitrogen flows, budgets, and use efficiencies over 35 years of organic and conventional cropping

Organic and conventional cropping systems differ in type and amount of nitrogen (N) inputs. In organic cropping only organic fertilizers are permitted, while both organic and mineral fertilizers are used in conventional cropping. Fertilizer type and amount can affect N use efficiency of a cropping system, but contributions via symbiotic N fixation and changes in soil N stocks are rarely quantified based on field data when computing nutrient budgets. We calculated an N budget that accounts for these contributions based on annual data records for a period of 35 years at the Swiss DOK (bio-Dynamic, bio-Organic, Konventionell) field experiment. Here, different organic and conventional cropping systems have been maintained at two fertilization levels: typical for the respective system, and half these doses (low). Controls comprise a conventional treatment receiving solely mineral fertilizers and an unfertilized treatment. At the typical level, average fertilizer N inputs were 93 (bio-dynamic), 96 (bio-organic), and 171 (conventional system) kg N ha−1 yr−1. Nitrogen output via harvested products regularly exceeded N input with fertilizers in all treatments. In each of the 7-year crop rotation periods, legumes (grass-clover ley, intercrops, soybean) were grown in three years. Their symbiotic N fixation was quantified based on 15N studies and legume N yield data. It ranged from 75 to 122 kg N ha−1 per year of the DOK experiment, was slightly reduced under low fertilization and was the main N input for most treatments. Soil surface budgets (sum of N inputs from fertilization, symbiotic fixation, seeds, and deposition minus N outputs via crop harvests) yielded balances from −31 kg N ha−1 yr−1 (in non-fertilized control) to +46 kg N ha−1 yr−1 (conventional system with typical fertilization level). Nitrogen use efficiencies (NUE; N output with harvests as % of sum of N inputs) reached values >100 % in treatments with negative balances while NUE ranged from 85 % to 99 % in treatments with positive balances. Changes in topsoil (0–0.2 m) N stocks over time ranged from −26 to +9 kg N ha−1 yr−1 and declined in both unfertilized and mineral fertilized controls, and in systems receiving animal manure at low fertilization levels. Thus, positive soil surface N balances and animal manure are needed to maintain or increase topsoil N stocks. While NUE was generally high in all cropping systems there remains a trade-off between either soil N mining at higher NUE or potential N loss to the environment at lower NUE.

The Effect of Long-Term Farmyard Manure and Mineral Fertilizer Application on the Increase in Soil Organic Matter Quality of Cambisols

Soil organic matter (SOM) quantity and quality are important factors that significantly influence soil fertility. SOM quality indicators change throughout time. In this study, long—term field experiments (22–50 years in duration) on a Cambisol at four sites in the Czech Republic were selected. Seven crops were successively rotated in the sequence: clover, winter wheat, early potato, winter wheat, spring barley, potato, and spring barley with interseeded clover. Five treatments were investigated, including an unfertilized treatment, farmyard manure, and various combinations of farmyard manure and mineral fertilization. A total of 40 t ha−1 of farmyard manure was applied to the early potato and potato crops. Combining organic and mineral fertilizers increased soil organic matter quality and quantity over unfertilized or organic only treatment. The highest intensity of mineral fertilizers in our trials elevated the mean of carbon sequestration efficiency to 45.6% in comparison to pure manure treatment which reached only 22.9% efficiency. A strong correlation was established between the total glomalin content and soil organic matter carbon, fulvic acid, humic acid, carbon hot water extraction, potential wettability index (PWI), and aromaticity index. The PWI was also strongly correlated with these indicators. The E4/E6 ratio indicator was shown to be a much less sensitive method for reflecting the change in soil organic matter quality.

Mineral Nitrogen Release Patterns in Various Soil and Texture Types and the Impact of Urea and Coated Urea Potassium Humate on Barley Biomass

Controlled-release urea fertilization is an innovative approach and effective means to reduce the loss of nitrogen and enhance fertilizer use efficiency to optimize crop yield while minimizing the environmental impact. The objective of this study was to investigate the dynamic process of mineral nitrogen (Nmin) release in Luvisols, Cambisols, Retisols, and Arenosols to understand the interaction between soil characteristics and mineral nitrogen release and evaluate the impact of conventional urea compared to coated urea potassium humate on barley biomass production. A pot experiment was conducted under glasshouse conditions (20 ± 2 °C and 60% Humidity). Five treatments including no fertilization as a control (C), 100 kg·N·ha−1 of urea (U100), 200 kg·N·ha−1 of urea (U200), 100 kg·N·ha−1 of coated urea potassium humate (UPH100), and 200 kg·N·ha−1 of coated urea potassium humate (UPH200) were applied to four soil and texture types. Our findings indicate that there are different patterns of mineral nitrogen release across the different soil and texture types. Ammonium levels reached their peak point in all soils within 2–7 days after application. On the other hand, the concentration of nitrate NO3−–N showed a linear increase over 45 days during the experiment. The Retisol, which had a sandy clay texture, obtained the highest concentration of mineral nitrogen in both forms (NH4 and NO3), while the sandy texture of Arenosol showed the lowest accumulation of mineral nitrogen and its forms. The application of potassium humate caused a delay of 1–4 days in the peak of soil ammonium, which at peak accounted for approximately 25–44% of the mineral nitrogen in the soil. Furthermore, the application of urea and coated urea potassium humate exhibited significant effects on barley biomass with an increase of approximately 14–91% compared to the unfertilized treatment (control). This research contributes to our understanding of nutrient dynamics in diverse soil environments and provides insights into optimizing sustainable fertilization strategies such as controlled-release fertilizer application. The implications of these findings highlight the significance of tailored nutrient management practices based on soil texture type, which can lead to improved agricultural productivity and environmental impact.

Long-Term Application of Manure and Different Mineral Fertilization in Relation to the Soil Organic Matter Quality of Luvisols

Long-term field experiments were conducted on luvisol at five sites in the Czech Republic (42–48-year duration). The average total organic carbon content in the soil varied between 9.0 and 14.0 g kg−1. In these trials, seven crops were rotated in the following order: clover, winter wheat, early potato, winter wheat, spring barley, potato, and spring barley with interseeded clover. Five treatments were studied: unfertilized treatment (Con), farmyard manure (F), and combinations of farmyard manure with three mineral fertilization levels (F+M1, F+M2, F+M3). Plant residues were not incorporated into the soil. An amount of 40 t ha−1 of farmyard manure fresh matter was applied twice during crop rotation. Intensive mineral fertilizer (F+M3) increased the average value of the carbon sequestration efficiency (CSE) by 12.9% and up to 26.3%. Combining organic and mineral fertilizers at moderate and higher intensities increased the soil organic matter quantity and quality compared to the unfertilized or manure treatment. Data on the glomalin content can be used to study the organic matter quality. We determined a strong correlation between the total glomalin content and the soil organic matter carbon, fulvic acid content, humic acid content, extractable carbon content, and dissolved organic carbon content, as well as the potential wettability index and aromaticity index.

Evaluation Effect of Inoculum Prepared from Local Bacterial Isolates of Rhizobium and Nitrogen Fertilization on some Growth Traits of Mung Bean Plant in Gypsiferous Soil

The root nodule bacteria are utilized in the production of natural biological fertilizers to achieve clean agriculture by reducing chemical fertilizers. Therefore, the bacterial inoculum was prepared from local isolates of Rhizobium leguminosarum and Bradyrhizobium japonicum, which were morphologically and molecularly characterized. Subsequently, the efficacy of the prepared inoculum was tested in the formation of root nodules and some growth traits of mung bean plants in gypsiferous soil at three levels of nitrogen fertilization (0, 40, 80) kg N ha-1 The results showed a significant increase in all plant growth traits during the flowering stage for the treatments inoculated with Rhizobium leguminosarum and Bradyrhizobium japonicum bacteria in comparison to the treatment without inoculation. The inoculated treatments outperformed the non-inoculated treatment significantly. Additionally, the treatment inoculated with Bradyrhizobium japonicum showed a significant superiority over the treatment inoculated with Rhizobium leguminosarum in all studied growth traits, the recorded values for the count of root nodules were (0.00, 8.33, 35.11) nodule. plant-1, The wet mass of nodules was (0.00, 0.091, 1.802) g. plant-1, and dry mass of nodules was (0.00, 0.010, 0.337) g. plant-1. The plant height was (52.11, 56.22, 58.05) cm. plant-1. The dry mass of the vegetative part, was (14.03, 20.10, 23.05) g. plant-1, and, the dry mass of the root part was (1.37, 2.57, 2.67) g. plant-1. The nitrogen content was (1.547, 2.765, 3.028) % phosphorus (0.121, 0.236, 0.377) %, and potassium (1.168, 2.342, 3.562) % in the vegetative part. The absorbed nitrogen in the vegetative part was (217.41, 541.10,718.02) mg. plant-1. These values were recorded for the non-inoculated treatment, Rhizobium leguminosarum inoculated treatment, and Bradyrhizobium japonicum inoculated treatment, respectively. The results showed a significant superiority for the 40 kg N ha-1 fertilized treatment in comparison to both the unfertilized treatment and the 80 kg N/ha-1 fertilized treatment in all studied traits. The interaction effect was significant, as the treatment that was inoculated with Bradyrhizobium japonicum and 40 kg N ha-1 fertilized treatment exhibited significant superiority over the other treatments in all studied traits.

Soil water dynamics and biomass production of young rooibos (Aspalathus linearis) plants

Rooibos (Aspalathus linearis) is endemic to certain regions of the Western- and Northern Cape of South Africa, where it is also commercially grown. Being low-rainfall regions, information on the soil water balance of rooibos is essential, but such data is limited. Consequently, the effect of inorganic fertilisation and soil depth on soil water dynamics in a young rooibos plantation at Nardouwsberg, Western Cape were studied. Soil water content of plots planted to unfertilised and fertilised plants as well as that of bare soil were determined over the duration of the 2016/17 season. All treatments were replicated on shallow and deep soils sites and plant growth was determined at the end of the season. At the end of the study, the profile soil water content and evapotranspiration of the bare and planted plots were similar which prove that fallowing (water harvesting) is not an option in the sandy soils of this region. With the exception of the 20−30 cm root zone of the planted plots at the deep site, the water content decreased to levels below the permanent wilting point in the soil profile during summer. It was concluded that rooibos plants could survive through an adapted root system. A further survival method was proposed, involving moisture moved through evaporation from the deeper soil layers into the drying-front in the ~ 10−30 cm soil layer where a condensation-evaporation cycle enables rooibos to harvest small amounts of water. The highest shoot biomass with the longest taproot resulted from the unfertilised treatment on the deep soil thanks to higher soil water content, whereas the shoot and root biomass of the fertilised treatment at both sites were low due to high P soil concentration. This study revealed that unfertilised plants on deeper soils result in higher rooibos production under drought conditions.

Animal manure digestate fertilization effect on the soil microbial activity and crop productivity in the northern part of temperate climate conditions-Lithuania

Microbial communities make up a significant portion of the soil, and their activity is crucial to the soil's ability to function. In this study, we aim to evaluate the influence of animal waste-based digestate as N source on soil microbial activity and crop productivity over a three-year period in a crop rotation system. Two experimental field trials using the same design were performed in the year 2018–2020 and 2019–2021, respectively. Four different fertilization treatments, namely Synthetic Nitrogen, Chicken manure digestate, Cow manure digestate, and Pig manure digestate split fertilized (90 kg ha−1 N and 80 kg ha−1 N), and unfertilized treatment (control) were studied while growing different annual crops (spring wheat, triticale, and barley). There was a more significant positive effect on the soil microbial biomass carbon noticeably observed after the first year of digestate application, with an increase of 20.2–75% when compared to the unamended soil. Soil dehydrogenase activity was a less sensitive indicator for the effect of fertilization on soil biochemical activity, but the average data from both experiments showed an increase in fertilized soils from 6.6 to 8.5% in fertilized soils. The soil moisture did not significantly influence the microbial biomass and the enzymatic activity. However, crop productivity consistently rose each successive year, a positive effect of digestate use. We deduced that the long-term application of animal manure digestate under natural conditions coupled with other variable factors such as seasonal conditions and agricultural management techniques significantly influenced the microbial biomass contents – a critical component of the biological state of the soil. Our findings will help identify how and what could make soil microbial communities and crop productivity vulnerable to seasonal changes in relation to the consistent application of animal manure digestate to agricultural soils and the agricultural techniques employed.

Exploring Phosphorus Fraction Dynamics in Loess Soils: Impact of Long-Term Nitrogen and Phosphorus Fertilization on Cropland and Fallow Land

Long-term cropping systems require balanced phosphorus (P) management for better yield and environmental sustainability. However, the soil P transformations under fallow rotations with and without long-term nitrogen (N) and P fertilization largely remained unknown. This study evaluated the status of P forms in loess soils in response to varied combined rates of N and P fertilizers, tillage management practices, fallow land systems (natural fallow (NF), and bare fallow (BF)). Four NP treatments (N0P0, control; N0P100, 100 kg P ha−1; N160P0, 160 kg N ha−1; and N160P100), and two treatments with no fertilizer application and crops (NF and BF) were conducted. The treatments N0P100 and N160P100 significantly increased soil total P, inorganic P (Pi), organic P (Po), and Olsen P concentrations compared to the control, NF, and BF treatments. Labile P fractions (NaHCO3-Po and NaHCO3-Pi) were 7.30% and 11.8–12.4% higher in fertilized treatments than in control, NF, and BF treatments. The moderately labile NaOH-Pi was stable in all treatments, but NaOH-Po significantly decreased in the NF (2.60%) and BF (1.40%) treatments compared to the control and fertilized treatments; however, HClD-Pi was 59.1–66.0% higher in NF and BF compared to the control and fertilized treatments. Non-labile P (HClC-Pi and HClc-Po) fractions showed no significant difference between the fertilized and unfertilized treatments. Residual P levels were substantially greater in the P fertilized (N0P100) treatment than in the fallow treatments. The conceptual framework and redundancy (RDA) analysis revealed that the labile (NaHCO3-Pi and NaHCO3-Po) and moderately labile P fractions (NaOH-Po, NaOH-Pi, and HClD-Pi) were substantially associated with Olsen P contents, grain yield, and P uptake. Higher moderate fraction concentrations in fallows and their positive correlation with yield, P uptake, and Olsen P predict the importance of reserved P in these soils upon long-term fertilization, suggesting the utilization of P legacy and optimizing fertilizer applications.

Nitrogen dynamics after slurry application as affected by anaerobic digestion, biochar and a nitrification inhibitor

AbstractAnimal manures are valuable multi‐nutrient fertilizers, but their short‐term nitrogen (N) use efficiency (NUE) by plants is low, bearing the potential of harmful N losses to the environment, such as nitrate () leaching. To develop strategies to increase the NUE of cattle slurry, a comprehensive understanding of slurry N dynamics in the soil–plant system is needed. In a 57‐day microcosm experiment in the greenhouse, we assessed the effect of different slurry treatments on slurry N turnover in the soil and its uptake by ryegrass (Lolium multiflorum var. Westerwoldicum). Employing a two‐factorial design, 15N cattle slurry (SLU), 15N anaerobically digested cattle slurry (SLA), and 15N anaerobically digested cattle slurry plus biochar (SLA+) were combined with and without the nitrification inhibitor 3,4‐dimethyl‐1H‐pyrazole monophosphate (DMPP). As references, a mineral fertilizer (MIN) and an unfertilised treatment (N0) were included. The 15N recovery, hence NUE, in plant biomass was higher for SLA than for SLU, while recovery in soil at 55 days after set‐up showed an opposite trend, with over 45% of N from SLU still being recovered in soil. DMPP and biochar only marginally affected NUE and fertilizer N recovery in soil. Although 15N recovery in soil was highest for SLU, residual N leaching from SLU was low (<1% of added N). We attribute this to the limited presence of slurry N in mineral forms at this point of time, with the majority being stored in the non‐microbial organic soil N pool. Leaching of residual N from MIN was significantly higher for MIN than for SLU, while SLA and SLA+ ranged in between. Overall, anaerobic digestion appeared suitable for increasing NUE of cattle slurry, but further investigations under field conditions are necessary in order to assess its potential to reduce nitrate leaching in the long‐term.