Long-term Nutrient Management Research Articles

Releasing Patterns of Potassium and its Relationship with Different Forms of Potassium in Acid Alfisols Soils of Ranchi, Jharkhand, India

A study was conducted during 2017-2018 at the Experimental Farm of Birsa Agricultural University, Kanke, Ranchi, Jharkhand, India to assess the releasing patterns of potassium and its relationship with different forms of potassium in surface (0-15 cm) and sub-surface (16-30 cm) soils of acid alfisols from the selected 9 treatments under long-term nutrient management practices in maize-wheat cropping system. The releasing power of soil potassium is an index of the availability of the nutrient to the crops over a longer duration and in general, it indicates the sum of water-soluble K, exchangeable K, and a fraction of non-exchangeable K which is not immediately available to the growing plants, but will be slowly available over a longer period. Repeated extraction with boiling 1N HNO3 has been suggested as one of the methods to assess the potassium-releasing capacity of soils. In this context, cumulative K, constant rate K, and step K as a part of non-exchangeable potassium proposed by Haylock (1956) measure the potassium-releasing capacity of soils more effectively under intensive crop cultivation. The amount of K release in successive extraction with boiling 1N HNO3 decreased consistently and reached a plateau at the 8th and 9th extraction steps in both depths of soils. Cumulative K is highest in INM (T6) while constant rate K and step K are highest in Lime, FYM, P2O5, and K2O treated plots (T8). The lowest contribution of potassium release patterns is generally observed in the control plot (T1). Also, the K release was found to be maximum in surface soils than in sub-surface soils concerning various selected treatments. Cumulative K, Constant- rate K, and Step K had highly significant and positive correlations with different forms of potassium (Water soluble K, Exchangeable K, Non-Exchangeable K, Total K, and Lattice K) in both depths. The potassium-releasing patterns evaluated through cumulative K, constant rate K, and step K could be meaningful for making fertilizer recommendation programmes, especially in intensively cultivated areas. Hence, the importance of study in terms of the possible contribution to plant available pool of soil K through potassium release patterns in two depths of given soil has been pointed out.

Impacts of Long-Term Nutrient Management Based on Soil Test and Crop Response on Soil Health and Yield Sustainability in Typic Haplustalf

We studied the effect of soil tests and crop response-based long-term nutrient management on yield sustainability and soil health under rice-rice system in a Typic Haplustalf. The experiment was designed in randomized block design having five treatments, viz, control, the recommended dose of fertilizer (RDF), STCR–NPK for target yield of 6 t ha–1 for kharif rice and 5 t ha–1 for rabi rice (STCR–NPK6), STCR–NPK for 7 t ha–1 for kharif rice and 6 t ha–1 for rabi rice (STCR–NPK7), and STCR–IPNS for 7 t ha–1 for kharif rice and 6 t ha–1 for rabi rice (STCR–IPNS7), and these treatments were replicated thrice. The 10-year mean data suggested that minimum yield was observed from control whereas highest was achieved in STCR–IPNS7 in both kharif as well as rabi seasons. The highest sustainable yield index (SYI) was 0.93 in kharif and 0.77 in rabi rice was observed under STCR–IPNS7, and lowest in control. Soil fertility status revealed that disregard for external application of nutrients resulted in depletion of 108 kg N, 11.6 kg P, and 200 kg K ha-1 and intensity of nutrient depletion was lowest in STCR–IPNS followed by STCR–NPK7, STCR–NPK6, and RDF. The urease, phosphatase, and dehydrogenase activities and microbial biomass C were found to be higher in STCR–IPNS when compared with other nutrient management practices while minimum values were recorded in the control.

Digital soil characteristics mapping for aiding site-specific management practices in the West Nile Delta, Egypt

Soil survey system is the key word for sustainable soil use and management. This study aimed to generate a digital soil mapping (DSM) using various spatial resolutions of freely available digital elevation models (DEMs) i.e., (30 m ALOS “Advanced Land Observing Satellite”, 12.5 m ALOS, 30 m SRTM “Shuttle Radar Topography Mission”, and 90 m SRTM) to assess the spatial variability of soil physio-chemical characteristics in El-Beheira Province, Western Nile Delta. A total of 196 geo-referenced soil profiles were collected from agricultural fields, and the soil's contents of total nitrogen (TN), potassium (K), available phosphorous (P), calcium (Ca), sulfur (S), magnesium (Mg), zinc (Zn), copper (Cu), manganese (Mn), and boron (B) were analyzed. The study revealed that the soil's contents of TN, P, S, B, and Cu were low, and Mg was suspected to be higher than K, leading to an Mg-induced K shortage. The study also found wide-ranging spatial variability structures of inverse distance weight (IDW) interpolated maps for several soil physio-chemical characteristics. The DSM further revealed that poor status was present in 85.4% of TN, 91.7% of P, 76.9% of S, and 87% of both B and Cu. The conclusion is that soil variability, as demonstrated in DSM, outweighs uniform treatment, and this discovery will assist extension workers, scientists, and decision-makers in implementing site-specific nutrient management strategies. Validation of the DSM is recommended for crop and variety-specific nutrient treatment rates. Understanding the geographical variance in the soil is critical for long-term nutrient management and higher output.

Change in phosphorus availability, fractions, and adsorption-desorption by 46-years of long-term nutrient management in an Alfisol of eastern India

In acid soils, majority of the applied phosphorus (P) transforms to sparingly soluble Fe (PFe) and Al phosphates (PAl), triggering rampant P deficiency. This study aimed to evaluate the impact of long-term (46-years) nutrient management practices on P fractions and P adsorption-desorption behaviour of an acid soil with a soybean-wheat cropping system. Out of ten treatments employed in this experiment, eight most pertinent to the study, viz., control, N (100 % of recommended N fertilizer), NP (100 % of recommended N and P fertilizers), 50 % NPK (50 % of recommended N, P, and K fertilizers), NPK, 150 % NPK, NPK+FYM (100 % of recommended N, P, and K fertilizers with farmyard manure), and NPK+Lime (100 % of recommended N, P, and K fertilizers with lime) were selected. The findings revealed that amorphous Fe and Al, which play a significant role in P fixation, increased due to cultivation. The treatment 150 % NPK recorded the highest available P (104 mg kg-1), followed by NPK+FYM (84.1 mg kg-1) at 0–15 cm depth. The PFe was the dominant inorganic P fraction (25–46 %) while soluble and loosely bound P (the easiest plant available fraction) was the lowest (0.9–1.9 %). The long-term cultivation led to an accumulation of PFe and PAl fractions while caused dissolution of calcium bound P (PCa). The highest content of organic P (Po) was recorded with NPK+FYM (234 kg ha-1). The analysis of Langmuir and Freundlich isotherms indicated that NPK+FYM and 150 % NPK reduced the P adsorption maxima to 341 and 231 mg kg-1, respectively, compared to 406 mg kg-1 for NPK. Moreover, these treatments increased the P sorption saturation to 33 % and 37 %, respectively, as compared to 12 % for NPK, and significantly enhanced P desorption, raising concerns about eutrophication. A path analysis was carried out to elucidate the effects of P dosage, liming, and manuring on soil properties, available P, P adsorption-desorption parameters, yield, and P uptake. In summary, the NPK+Lime treatment offered the most balanced approach, improving both crop yield and P uptake while effectively managing P dynamics in the soil. On the contrary, long-term application of NPK+FYM in an acid soil may result in faster P saturation of adsorption sites and increase the chances of leaching and eutrophication. Furthermore, tailored P fertilization strategies should be developed to better utilize the PFe and PAl fractions and supplementing applied P.

Effect of Nutrient Management Practices on Carbon Pools Following 13 Year of Cropping with Soybean (Glycine max) Based Cropping Systems in Vertisol of Central India

Organic manure application has its significant impact on the soil health. Low organic matter in tropical soils is a major factor contributing to their poor productivity. Soil properties have been continuously influenced by the management practices and land uses, in which latter one has been, identified as profound influence on soil properties especially on soil organic carbon. A thirteen year experiment on soybean based cropping system in a vertisol of central india under organic farming was used for this investigation An investigation was carried out on “Soil organic carbon dynamics under long-term nutrient management in soybean based cropping system” at the Indian Institute of Soil Science, Bhopal on an on-going research project on organic farming. The effect of organic, integrated and inorganic nutrient management was assessed in three cropping systems viz. soybean (JS 335)-wheat (Malwa Shakti), soybean-mustard (Pusa Bold) and soybean-gram (JG 130) on aggregate size fractions, carbon content in aggregate as well as soil organic carbon pools dynamics on a split plot experimental design with three replications. The study relevant to dynamics of soil organic carbon pools revealed higher content of soil organic carbon, labile carbon, water soluble carbon, SMBC as well as dehydrogenase activity that varied between 1.04 and 0.86 percent; 440 and 538 mg kg-1, 52.97 and 70.43; 288 and 375 mg kg-1, 88 and 137 µg TPF g-1 soil d-1, respectively in surface 0-15 cm soil under organic nutrient management.

Effects of long-term nutrient management in semi-arid Vertisols on soil quality and crop productivity in a cotton-greengram intercropping system

Effects of long-term nutrient management in semi-arid Vertisols on soil quality and crop productivity in a cotton-greengram intercropping system

Impact of Long-Term Nutrient Management on Carbon Dynamics under Cluster Bean-Wheat Cropping System in Western Rajasthan, India

A field experiment was started in 2008 under All India Co-ordinated Research Project- Soil Test Crop Response in western Rajasthan to study the long-term effects of nutrient management strategy using Soil Test Crop Response (STCR) approach on cluster bean– wheat cropping system. The present investigation indicated effects of organic compost and inorganic fertilizer as per soil test crop response approach basis on soil carbon dynamics. The treatments consisted of general recommended dose, target yield 15 q ha-1, target yield 15 q ha-1 with Integrated Plant Nutrient System (IPNS), target yield 20 q ha-1 and target yield 20 q ha-1 without Integrated Plant Nutrient System. The soil organic pools were studied after 9 years and it was found that the total C and its different pools of soil increased significantly under target yield 20 q ha-1 with IPNS. Active and passive pools (AP and PP) of carbon of soil increased significantly under target yield 20 q ha-1 with IPNS as compared to the target yield 15 and 20 q ha-1 treatments without IPNS and at par with target yield 15 q ha-1 with IPNS. Carbon management index (CMI) and carbon stock (CS) increased significantly under target yield 20 q ha-1 with IPNS. It can be concluded that combined application of organic and inorganic nutrient in long term basis significantly enhance carbon sequestration rate, consequently soil quality.

Carbon and Nitrogen Mineralization Kinetics in Soil Under Differential Nutrient Management Regimes in Inceptisols of Coastal India

ABSTRACT In intensive cropping systems, nutrient, and residue management techniques have a tendency to change the soil’s carbon (C) and nitrogen (N) cycle and, consequently, its potential for sequestration and loss. To understand the carbon and nitrogen mineralization kinetics, laboratory incubation studies were conducted with soils at variable depths from a long-term nutrient management experiment on cereal-vegetable-pulse cropping system. The experiment was laid out completely randomized design with 10 treatments replicated thrice. Long-term integrated application of inorganics with organics, biofertilizers, and amendment along with crop residues showed higher carbon and nitrogen mineralization potential and lower potential was observed in soils where crops were raised without application of any nutrient inputs (control) and uncultivated fallow. It was calculated that the potential for higher levels of carbon and nitrogen mineralization existed in the surface (0–15 cm) and subsurface (15–30 cm) layers, respectively, and was negligible in the deeper layer (30–45 cm). The mineralization rate was initially faster up to 42 days of incubation, indicating proper utilization of readily decomposable soil organic matter in the labile pools and thereafter found to slow down. Addition of lime along with the integrated use of organics and inorganics has found to raise the pH to a level that provides a suitable soil environment which affects the carbon and nitrogen mineralization kinetics resulting in buildup of total organic carbon and total nitrogen in the soils. The first-order kinetic model was the best fit in explaining the kinetic parameters of C and N mineralization. Soils under integrated nutrient management (INM) with farmyard manure (FYM) along with biofertilizers, amendment, and inorganic nutrients exhibited better carbon dynamics higher C mineralization (Cmin), potentially mineralizable C (C0), rate of C mineralization (dCmin/dt), and C mineralization quotient (qM), whereas soils applied with similar combinations with vermicompost was found effective for better nitrogen dynamics in terms of enhanced N mineralization (Nmin), potentially mineralizable N (N0), rate of N mineralization (dNmin/dt) and active N fraction over control and fallow soils. Integrated application of inorganic and organic inputs with crop residues over the years has shown beneficial impacts on soil carbon and nitrogen mineralization processes and their kinetics.

Effect of Inorganic and Integrated Long-term Nutrient Management on DTPA-extractable Micronutrients in a Vertisol under Soybean-wheat Cropping System across the Soil Depth

The status of DTPA extractable micronutrient (Zn, Cu, Fe and Mn) in response of continuous application of different inorganic and organic fertilizer combination in a 48 years old ongoing long-term fertilizer experiment (AICRP-LTFE) were investigated in Vertisol at Department of Soil Science, and Agricultural Chemistry, JNKVV, Jabalpur under intensive cultivation of soybean- wheat cropping system in 2021. The treatments selected for the study were: control (T1); 100% NP(T2); 100% NPK (T3); 100% NPK+FYM (T4); 100% N(T5); 50% NPK (T6); 150% NPK (T7). Application of FYM along with balance fertilizer (100% NPK) significantly increased the micronutrients availability in soil. On contrast, Imbalance fertilization caused a lower level of micronutrients in soil even below to the critical limit in case of zinc. A decreasing trend with increase in soil depth irrespective of type of nutrient management and micronutrient type was evident in the study. Findings of the present study emphasized the application of balance fertilization along with organic sources like FYM for sustaining micronutrients availability in Vertisol under soybean-wheat cropping system.

Impact of Long-term Nutrient Management Practices on Physical Properties of a Vertisol in Central India

Health of any soil is influenced by its physical properties to greater extent which has been more prominent in Vertisols due to their self-till behavior. Differential application of nutrients in long-term may alter the soil properties at temporal and spatial scales. Inventory on effect of different long-term nutrient management practices on physical properties across the soil depths, especially on Vertisols of central India, is insufficient. Present study examined the long-term (48 years) effect of different combinations of organic and inorganic nutrient management practices under soybean-wheat cropping system on various physical properties (Bulk density, Particle density, Porosity and Water holding capacity) of a Vertisol in of central India. In the present study, soil sample were collected at four depths (0-15, 15-30, 30-45 and 45-60 cm) in triplicate from seven treatments (Control, 100% NP, 100% NPK, 100% NPK+FYM, 100% N, 50% NPK and 150% NPK) of permanent plots of AICRP on LTFE (initiated in 1972), Jabalpur. By differential nutrient management practices the bulk density and porosity affected significantly up to 30 cm soil depth and beyond that up to 60 cm non-significantly. At all selected soil depths, water holding capacity were significantly affected. On contrary, a non-significant effect was observed on particle density by various nutrient managements. This study indicated a positive impact of balance fertilizer application and integrated approach of nutrient management on physical properties of soil.

Toward Soil Nutrient Security for Improved Agronomic Performance and Increased Resilience of Taro Production Systems in Samoa

A progressive decline in soil fertility in taro (Colocasia esculenta L., Schott) production systems has contributed to reduced crop productivity and farm profitability, and is recognized to be a threat to soil nutrient and food security in Samoa. Evidence based on three years of field experimentation showed that appropriate nutrient budgeting is required to reduce soil nutrient deficits and mitigate soil organic carbon loss. Balanced crop nutrition coupled with appropriate crop husbandry can significantly improve productivity and narrow yield gaps. A framework to guide nutrient recommendations for taro production systems is presented and discussed. This framework proposes that recommendations for N be derived from the yield-to-N response function (from which the most economic rate of N can be estimated) and that for other nutrients, namely P, K, Ca, and Mg, recommendations be based on replacement. The replacement strategy requires the development of soil nutrient indexes, which can be used to define the long-term nutrient management policy at the field scale. This long-term policy is informed by soil analyses, and it will determine whether existing soil nutrient levels are to be maintained or increased depending on the focus (productivity, profitability, environmental protection). If soil nutrients were already at an agronomically satisfactory level, their application may be omitted in some years to help reduce crop production costs, improve use efficiency, and ensure environmentally safe levels in soil are not exceeded.

Impact of long-term nutrient management on soil quality under cluster bean-wheat cropping system in hyper arid region

Impact of long-term nutrient management on soil quality under cluster bean-wheat cropping system in hyper arid region

Long-term nutrient management effects on soil aggregation and C stabilization in Vertisols of Central India

Long-term nutrient management effects on soil aggregation and C stabilization in Vertisols of Central India

Long-term nutrient management in an intensive rice-wheat cropping system improves the quantities, qualities, and availability of soil sulfur

In the last few decades, the deficiency of sulfur (S) has been noticed in the agricultural soils of India. Meanwhile, researchers reported that S plays a significant role in the productivity of the rice-wheat cropping system (RWCS). For the quantification of S response, a long-term field experiment was started at the Indian Council of Agricultural Research-Indian Institute of Farming Systems Research (ICAR-IIFSR), Modipuram, India. In total, 7 nutrient supply options were applied, i.e., organic, mineral fertilizer in the combination of integrated plant nutrition system (IPNS), and IPNS + berseem (B)/IPNS + cowpea (C) in the S availability of the soil in the RWCS. The results showed that the highest contribution in S availability by the total S (39%) is followed by the organic S (35%), sodium bicarbonate extractable sulfur (NaHCO3-ES; 7%), heat-soluble sulfur (SS; 7%), water-soluble sulfur (WSS; 4%), available S (4%), and inorganic S (4%) under different long-term nutrient supply options of RWCS. The continuous application of organic fertilizer and various IPNS options, such as the inclusion of pulses, significantly improved all S fractions in the soil and also offers an additional benefit in terms of sustainability of production and soil health as compared to the inorganic fertilizer fields. Overall, the results showed that IPNS showed its superiority over the rest of the treatment. The results also supported that the inclusion of pulses gives a further gain in terms of sulfur availability in soil systems under RWCS.

Elucidating phytoplankton limiting factors in lakes and reservoirs of the Chinese Eastern Plains ecoregion.

Knowledge of phytoplankton limiting factors is essential for cost-efficient lake eutrophication management. Herein, we propose a statistical framework to explore site-specific phytoplankton limiting factors and their dependence on water depth (WD) in 54 lakes in the Chinese Eastern Plains ecoregion. First, the maximal chlorophyll a (Chla) response to total N (TN) or P (TP), representing a region-specific "standard" model where phytoplankton were primarily N- or P-limited, was quantified using a 95% quantile regression. Second, site-specific limiting factors were identified using analogical residual analysis. N- or P-limitation was inferred if FractionTN (i.e. fraction of Chla observed and predicted by the "standard" model for a given TN)>0.95 or FractionTP >0.95; if both FractionTN and FractionTP <0.95 in a specific environmental condition (e.g. high non-algal turbidity), light limitation was suggested. As a result, 5%, 7%, 4%, 36%, 16%, 2%, and 30% of the sampling sites were limited by N, P, N+P, light availability, rapid flushing, abundant macrophytes, and unmeasured factors, respectively. Bloom control suggestions in the short run are proposed considering these actual limiting factors. Furthermore, the maximal FractionTN or FractionTP response to WD was explored, reflecting the effect of WD on FractionTN (or FractionTP) without significant confounders. The results indicated that phytoplankton in the studied freshwaters would be potentially light-limited, N-limited, N+P-co-limited, or P-limited depending on WD (<1.8, 1.8-2.1, 2.1-5.2, or >5.2m, respectively), because N will gradually become surplus with increasing WD, while at very shallow depths, strong sediment re-suspension induces light limitation. This finding implies that long-term nutrient management strategies in the studied freshwaters that have WDs of 0-2.1, 2.1-5.2, and >5.2m can entail control of N, N+P, and P, respectively. This study provides essential information for formulating context-dependent bloom control for lakes in our study area and serves as a valuable reference for developing a cost-efficient eutrophication management framework for other regions.

Impact of long-term nutrient management on sequestration and dynamics of soil organic carbon in a semi-arid tropical Alfisol of India

We aim to determine the effect of long term application of organic and inorganic nutrients on carbon sequestration and related biological attributes of a semi-arid tropical soil under an intensive maize-sunflower cropping system in India. The century-old experimental soil was assessed the impact of nutrient management on carbon sequestration, labile and passive pools of soil organic carbon, and soil biological attributes. The topsoil (0–25 cm) and subsoil (25–50 cm) samples from unfertilized (control), chemical fertilizer applied (IC), organic manure amended (OM), and integrated nutrient management adopted (INM) plots were analyzed for carbon sequestration and dynamics. The INM and OM treatments had a mean annual carbon sequestration rate of 0.18 Mg and 0.14 Mg carbon per ha, respectively. The continuous addition of organic amendment (12.5 t ha−1 year−1 of farmyard manure) with or without chemical fertilizer improved both topsoil and subsoil active carbon pools viz., microbial biomass carbon, labile carbon, water-soluble carbon, particulate carbon fraction, and passive pools like humic acid and fulvic acid significantly compared to synthetic fertilizer and unfertilized treatments. The Fourier-transformed infrared spectra of humic acids extracted from OM and INM treatment soils showed high humification, aromaticity, and redox with complex functional groups than IC and control treatment soils. OM and INM treatments significantly enhanced the abundance of carbon mineralizing gene (chiA) in topsoil and subsoil than IC and control treatments, while the carbon dioxide fixing gene (cbbL) had no apparent change due to nutrient management. Subsequently, the organics amended soils had better biological quality in terms of higher soil enzymes' activity, bacterial abundance, and respiration rate with lower metabolic quotient than chemical fertilized and control soils. The principal component analysis indicated that OM and INM treatment soils were distinctly positioned from IC and control treatment soils and the soil carbon fractions and soil enzymes were the significant factors influencing the nutrient management induced carbon sequestration. The active and passive carbon fractions, dehydrogenase, fluorescein diacetate hydrolysis, alkaline phosphatase, and substrate-induced respiration showed a strong and positive correlation with carbon sequestration of semi-arid tropical soil. Altogether, these findings indicated that the continuous addition of organic amendments would be a valuable practice to improve the soil carbon sequestration and carbon pools, and this practice is essential for the tropical soils with intensive farming to sustain the soil quality and agricultural productivity.

Fertilization Rapidly Alters the Feeding Activity of Grassland Soil Mesofauna Independent of Management History

Nitrogen fertilization of permanent grasslands affects soil fauna communities by modifying their taxonomic composition, population dynamics and feeding activity. However, it is not well understood if the edaphic fauna adapts to these external inputs so that the immediate response to fertilizer application depends on the long-term nutrient management strategy. We performed a field experiment in permanent grasslands under agricultural management in three regions across Germany. We used experimental fertilization with an organic plant-sourced fertilizer along a long-term nutrient management gradient to study the immediate and long-term effects of fertilization and their interdependence on the taxonomic composition and feeding activity of the soil mesofauna (Nematoda, Oribatida, and Collembola). Sampling season, soil properties, vegetation structure, and geographic location were considered as additional predictor variables to reflect heterogeneity in environmental conditions. The taxonomic composition, richness and total abundance of soil mesofauna communities were significantly affected by long-term nutrient management, but not by experimental fertilization. However, N pulses rapidly (within days) reduced the feeding activity estimated with bait-lamina strips independent of long-term nutrient management strategies. Experimental addition of organic plant-sourced fertilizer may have led to a rapid build-up of microbial biomass, providing alternative food sources for the soil mesofauna and causing a shift away from the bait-lamina substrate. Our study indicates that community changes associated with the long-term nutrient management regime in permanent grasslands do not alter the strong functional response of the soil mesofauna to N pulses. There is an urgent need to develop nutrient management strategies for permanent grasslands that take into account both the conservation of the edaphic faunal community and changes of ecosystem functions caused by rapid responses of the soil mesofauna to fertilizer inputs.

Fractions of Soil Potassium and their Depthwise Distribution under Long-Term Nutrient Management Practices in Semiarid Alfisols in India

A field experiment was conducted on a long-term experimental plot during two consecutive rabi seasons of 2016-17 and 2017-18 at the college farm, College of Agriculture, Rajendranagar, Hyderabad, PJTSAU. The experimental soil was non-saline, neutral in reaction with sandy loam texture. Different forms of soil potassium were studied with six different nutrient management practices in randomized block design with four replications. The results of pooled data of two years study revealed that significantly higher contents of water soluble potassium (17.77 mg kg-1), exchangeable potassium (568 mg kg-1), nonexchangeable potassium (999 mg kg-1) and Total potassium (1.80%) in surface layer (0-15 cm) at flowering were recorded with integrated application of 50% N through FYM and 50% N through chemical fertilizers and it was on par with treatment applied 100% RDF through chemical fertilisers and significantly superior over other organic nutrient management treatments. A similar trend was observed at all soil depths (15-30, 30-45, 45-60 cm) and all the contents were decreased from flowering to harvest. All potassium forms decreased with increasing the depth except non exchangeable K. All the fractions were found to be significant in surface layer (0-15 cm). The contribution of different forms of soil K to Total K was in the order of non-exchangeable K&gt; exchangeable K&gt; water soluble K and similar trend was observed in all soil layers.&#x0D;

Trade-off between soil aggregate stability and carbon decomposition under 44 years long-term integrated nutrient management in rice-wheat-jute system

ABSTRACT Soil stability, yield decline and higher carbon decomposition are the key issues in intensive agriculture. Long-term integrated nutrient management (INM) influences carbon (C) dynamics and maintains the soil aggregate stability, which driven by the type of cropping system and climatic zone. Therefore, the specific effects of rice-wheat-jute cropping system on soil aggregate distribution, C-stability, and trade-off between C-storage and decomposition rate were studied of a long-term INM trial in the sub-tropical zone. We investigated the effect of four long-term nutrient management practices that include, control, N (nitrogen (N) and no phosphorus (P), and potassium (K)), NPK (N, P and K) and INM (N, P, K + farmyard manure (FYM)). Results showed that the addition of FYM with NPK improved macro-aggregates by 71%, and associated C-pools by 30%. The INM enhanced C-storage (20%), however, the decomposition rate was also higher (28%) over control at 35 °C at field capacity. A trade-off exists between the soil-aggregate stabilization and C-decomposition rate. The proportion of C-storage was higher than decomposition in INM. Further, the C-sequestration varied (0.17 to 0.26 t ha−1 y−1) under different treatments and were found highest in INM, indicating long-term soil stability and yield sustainability in the rice-wheat-jute system.

Effect of long-term nutrient management practices on soil health and paddy yield of rice-rice-fallow cropping system in tropic humid climate

Long-term repeated nutrient management practices may have impact on soil health and sustainable paddy (Oryza sativa) production. Therefore, a long-term (33 years) field experiment was conducted at Bangladesh Rice Research Institute in Gazipur with the objective of finding the impact of repeated inorganic and integrated nutrient management (INM) practices on soil biochemical properties, soil quality and its cumulative effect on paddy yield. Experiment was permanently laid out in a replicated complete block design with three replications and modern paddy varieties, BRRI dhan49 and BRRI dhan29, were grown in wet and dry seasons respectively. Treatments imposed were; balanced chemical fertilizer (BCF), K minus from BCF, P minus from BCF, N minus from BCF, Chemical fertilizer with 3 t ha−1 decomposed cowdung (CD), Chemical fertilizer with 2 t ha−1 decomposed poultry litter (PL) and Fertilizer control. The SOC decreased 8% due to 33 years BCF compared to initial soil and increased 18% in INM compared to BCF practice during last 10 years. Long term BCF practices did not bring significant changes in soil pH, however 0.09 units increased and 1.45% bulk density decreased in PL-INM practice. Urease and phosphatase activities, total bacteria, phosphate solubilizing bacteria, free-living N2 fixing bacteria, water stable aggregates, NH4+-N, available P, exchangeable K were increased in INM practices and between two INM treatments, PL was superior over CD. The highest SQI (0.93) and 10 years’ average paddy yield per season (4.99 t ha−1) was obtained in PL-INM followed by CD-INM (SQI, 0.80 and grain yield 4.12 t ha−1) and the lowest in the N minus from BCF practice (SQI, 0.16 and paddy yield 3.2 t ha−1) and control (SQI, 0.33 and paddy yield 2.9 t ha−1) treatment. SQI due BCF practice was 0.68 and average paddy yield was 4.36 t ha−1. The results of AreaSQI revealed that NH4–N, available P and enzyme activities are the most sensitive soil parameters that degraded due to different nutrient management practices. The study also proved that imbalance fertilizer application, especially removal of N nutrition, was the most detrimental for paddy soil quality and PL-INM treatment is the best nutrient management practice for maintenance of soil health in the hyperthermic vertic endoaquepts and tropical humid climate.