Uniform Distribution Of Nutrients Research Articles

Microvascular network based on the Hilbert curve for nutrient transport in thick tissue.

To address the uneven nutrient distribution within three-dimensional (3D) tissue models and organoids currently used in medical research, this study introduces a microvascular network based on the Hilbert curve. Our aim was to develop innovative solutions for enhancing nutrient supply in thick tissue models in vitro. By using 3D bioprinting, we engineered microvascular networks of varying Hilbert orders and validated their efficacy in enhancing nutrient uniformity through numerical simulations and experiments. These networks facilitated broader and more uniform nutrient distribution throughout the thick tissue models, particularly the 2° Hilbert microvascular structure, which occupies less space and significantly reduces regions of cellular death. Furthermore, we explored the potential of assembling larger tissue constructs using the 2° Hilbert microvascular network, showcasing its applicability in constructing large-scale biological models. The findings suggest that the 2° Hilbert microvascular structure is particularly effective in ensuring adequate nutrient delivery, thus enhancing the viability and functionality of large-volume tissue models. These innovations hold significant promise for advancing the fields of tissue engineering and regenerative medicine by improving nutrient delivery to in vitro thick tissue block models. This provides a robust foundation for future in vitro research and clinical applications, potentially leading to more effective treatments and interventions in the medical field. The development of these microvascular networks represents a crucial step forward in overcoming the limitations of current 3D tissue models and organoids, paving the way for more sophisticated and reliable biomedical research tools.

The Effect of Tillage Method on the Nutrient Regime of Soil during the Growing of Trifolium pratense

Abstract The article presents the results of studying the influence of tillage methods on the number of bacteria and fungi in the arable soil layer, nutrient indicators, and, consequently, the yield of Trifolium pratense. The purpose of the study is to determine how tillage affects the feeding regime and yield of Trifolium pratense. The research was conducted at the experimental field of the Educational and Scientific Research Center of Lviv National Environmental University. For the study of microorganisms in the arocenosis of meadow clover, soil samples were taken using a cylindrical drill from arable (0–20 cm) and sub-soil (20–40 cm) layers with an average weight of an individual sample of 300 g. For microbiological analysis, average samples from five individual samples were prepared. The isolation of the main agronomically useful groups of microorganisms from the soil was carried out by the method of microbiological sowing of soil extracts on solid nutrient media: for fungi – wort-agar, for bacteria – meat-peptone agar (MPA). The dilution of the soil extract for fungi and bacteria was, respectively, 1 : 1000; 1 : 100000. Microbiological seeding was performed in triplicate. The calculation of the total number of microorganisms in the soil was carried out by Tepper´s method. The yield of crops and the results of laboratory studies were processed by the method of variance analysis. The application of a tiered tillage allowed to increase the yield of Trifolium pratense green mass by 4.5 t·ha−1 (+17.0%) compared to the control (conventional plowing). It is established that tier ploughing with the PYA-4-40 plough promotes uniform distribution of nutrients in the arable soil layer and formation of homogeneous soil fertility. In such a soil environment, much more favorable conditions are created for the development of microflora and more intensive microbiological processes compared to the options of chisel and conventional (control) tillage, and, consequently, the formation of high yields of green Trifolium pratense.

Can plants integrate information on above-ground competition in their directional responses below ground?

Light competition can induce varying above-ground responses in plants. However, very little is known regarding the effect of above-ground light competition cues on plant responses below ground. Here we asked whether light competition cues that indicate the occurrence and direction of neighbours above ground might affect directional root placemat. In a common-garden experiment, we examined the integrated responses of the annual procumbent plant Portulaca oleracea to light competition cues and soil nutrient distribution. Soil nutrients were distributed either uniformly or in patches, and light competition was simulated using a transparent green filter, which was spatially located either in the same or opposite direction of the soil nutrient patch. As predicted, root proliferation of P. oleracea increased in the direction of the enriched soil patches but was homogenously distributed under the uniform nutrient distribution. Interestingly, root distribution was also affected by the light competition cue and increased in its direction regardless of the location of the soil patches. Our results provide initial support to the idea that below-ground plant responses to competition might also be regulated by above-ground neighbour cues, highlighting the need to further investigate the combined effects of both above- and below-ground competition cues on root behaviour.

Effects of pellet quality to on-farm nutrient segregation in commercial broiler houses varying in feed line length

Improving pellet quality ( PQ ) by increasing the percentage of pellets in finished feed is complicated. The hurdles of feed manufacturing are well documented. Researchers continue to investigate the effects of PQ on various performance parameters, yet additional PQ benefits must be presented to stimulate change in feed manufacturing practices. Therefore, the aim of this study was to investigate the effects of PQ on nutrient segregation in commercial broiler houses differing in feed line length. Four experiments ( Exp ) were performed, each including 4 replicate feed lines segmented into 8 regions. A commercial broiler finisher diet was manufactured using techniques to create either poor pellet quality ( PPQ ) or improved pellet quality ( IPQ ) feeds. Exp1 and Exp2 were conducted to investigate how PPQ and IPQ feed contributes to nutrient segregation in a 152-m feed line, respectively. Exp3 and Exp4 used the same PPQ and IPQ feed but were carried out in a 152-m house with split feed lines, 76-m long. Feed samples were taken from each feed pan per Exp. Pellets and fines were analyzed separately to determine pellet-to-fine ratio (P:F), pellet survivability, and nutrient concentrations. Segregation of amino acids and phytase were apparent in Exp1 (PPQ-152m), demonstrated by varying concentrations of amino acids and phytase activity across the 8 regions of the feed line ( P < 0.05). Phytase segregation was not apparent in Exp2 (IPQ-152m) ( P > 0.05). Threonine and phytase segregation occurred in Exp3 (PPQ-76m) ( P < 0.05), whereas no evidence of nutrient segregation was observed in Exp4 (IPQ-76m) ( P > 0.05). These data suggest that investing in PQ improvements provides a more uniform distribution of nutrients throughout the house.

Engineering the cellular mechanical microenvironment to regulate stem cell chondrogenesis: Insights from a microgel model

Biophysical cues (especially mechanical cues) embedded in cellular microenvironments show a critical impact on stem cell fate. Despite the capability of traditional hydrogels to mimic the feature of extracellular matrix (ECM) and tune their physicochemical properties via diverse approaches, their relatively large size not only induces biased results, but also hinders high-throughput screening and analysis. In this paper, a microgel model is proposed to recapitulate the role of 3D mechanical microenvironment on stem cell behaviors especially chondrogenesis in vitro. The small diameter of microgels brings the high surface area to volume ratio and then the enlarged diffusion area and shortened diffusion distance of soluble molecules, leading to uniform distribution of nutrients and negligible biochemical gradient inside microgels. To construct ECM-like microenvironment with tunable mechanical strength, three gelatin/hyaluronic acid hybrid microgels with low, medium and high crosslinking densities, i.e., Gel-HA(L), Gel-HA(M) and Gel-HA(H), are fabricated in microfluidic devices by Michael addition reaction between thiolated gelatin (Gel-SH) and ethylsulfated hyaluronic acid (HA-VS) with different substitution degrees of vinyl sulfone groups. Our results show that mouse bone marrow mesenchymal stem cell (BMSC) proliferation, distribution and chondrogenesis are all closely dependent on mechanical microenvironments in microgels. Noteworthily, BMSCs show a clear trend of differentiating into hyaline cartilage in Gel-HA(L) and fibrocartilage in Gel-HA(M) and Gel-HA(H). Whole transcriptome RNA sequencing reveals that mechanical microenvironment of microgels affects BMSC differentiation via TGF-β/Smad signaling pathway, Hippo signaling pathway and Integrin/YAP/TAZ signaling pathway. We believe this microgel model provides a new way to further explore the interaction between cells and 3D microenvironment. Statement of SignificanceIn recent years, hydrogels have been frequently used to construct 3D microenvironment for cells. However, their relatively large size not only brings biased experimental results, but also limits high-throughput screening and analysis. Herein we propose a gelatin/hyaluronic acid microgel model to explore the effects of 3D cellular mechanical microenvironment (biophysical cues) on BMSC behaviors especially chondrogenesis, which can minimize the interference of biochemical gradients. Our results reveal that BMSC differentiation into either hyaline cartilage or fibrocartilage can be regulated via tailoring the mechanical properties of microgels. Whole transcriptome RNA sequencing proves that “TGF-β/Smad signaling pathway”, “Hippo signaling pathway” and “Integrins/YAP/ TAZ signaling pathway” are activated or inhibited in this process.

Co-Granulated and Blended Zinc Fertilizer Comparison for Corn and Soybean

A new co-granulated formulation of monoammonium phosphate (MAP) including S and Zn could allow for more uniform nutrient distribution. A six site-year study evaluated the effects of blended phosphorus (P) sources [MAP and diammonium phosphate (DAP)] and zinc amounts (0, 2.2, and 5.6 kg Zn ha-1) compared to co-granulated fertilizer, MicroEssentials® Sulfur-10 (MES10™) (12-40-0-10S) and MicroEssentials Sulfur and Zinc (MESZ™) (12-40-0-10S-1Zn), on corn and soybean response. Fertilizers were broadcast applied for corn and the carry-over effect on soybean was determined. Ear leaf P, S, and Zn concentrations at Novelty in 2013 and 2014 were within the sufficiency range regardless of treatment, even though initial soil test values were low-medium. Yields were similar to the N only control for all site-years except at Novelty in 2013, where MAP+ZnSO4 at 2.2 kg Zn ha-1, MAP+Super Zn at 5.5 kg Zn ha-1, and DAP+AMS were 540 to 570 kg/ha greater. The amount of Zn fertilizer (2.2 vs. 5.6 kg Zn ha-1) also showed no significant effect on yield. Applications of P or Zn generally increased their concentrations in post-harvest soil samples. Fertilizer applied for corn indicated some differences in soybean plant nutrient concentrations, but it had no effect on total plant nutrient uptake, grain yield or quality. At Novelty, soybean plant Zn concentration was greater at 5.6 kg Zn ha-1 compared to 2.2 kg Zn ha-1, while Albany showed an increase in whole soybean plant Zn concentration with SuperZn compared to ZnSO4. Carry-over fertilizer from corn showed limited effects on soybean response the following year.

Heterogeneous distribution of soil nutrients increase intra-specific competition in the clonal plant Glechoma hederacea

Small-scale heterogeneity strongly affects plant fitness and many ecological processes, and it can significantly influence the growth of individual plants, populations and communities. Generally, clonal species achieve significantly more growth when essential resources are patchily distributed than when resources are uniformly distributed. In this study, we aim to determine the effect of spatial heterogeneity in soil resources on intraspecific competition in the clonal plant Glechoma hederacea. We report the outcomes of a greenhouse experiment where high and low densities of plants were exposed to patchy and uniform distribution of nutrients. Our results showed that patchy distribution of resources exacerbated intra-specific competition between clonal systems. We found a reduction of total mass of clonal systems growing at high-density, especially under patchy conditions. Patchy distribution of resources conduct to high concentration of resources located in small areas, and as consequence increase the competition interaction between plants. This study demonstrates that full understanding of plant–plant competitive interactions requires consideration of spatial heterogeneity in nutrient supply.

Nitrogen transformation and plant growth in response to different urea‐application methods and the addition of DMPP

AbstractThe differences in soil inorganic‐nitrogen (N) concentration and distribution, plant biomass, and root growth in the presence or absence of the nitrification inhibitor 3,4‐dimethylpyrazole phosphate (DMPP) under different urea‐application methods (placement versus homogeneously applied) were explored in a short‐term microcosm experiment. Spring wheat (Triticum aestivum L.) was grown in a microcosm with six different treatments: no amendment (CK), DMPP homogeneously applied (DMPP‐hom), urea homogeneously applied (Urea‐hom), urea with DMPP homogeneously applied (Urea + DMPP‐hom), urea placement (Urea‐place), and urea with DMPP placement (Urea + DMPP‐place). After 28 d, plant biomass, soil inorganic nitrogen content, distribution of soil inorganic nitrogen and plant roots in the soil were analyzed. The soil inorganic N and plant roots tended to be distributed asymmetrically in the placement treatment but were distributed symmetrically in the homogeneous treatment. DMPP addition significantly increased the soil NH$ _4^+ $‐N content and decreased the NO$ _3^- $‐N content, especially near the fertilized zones in the placement treatment. Compared to the urea‐only treatments, DMPP application significantly increased the shoot biomass and root lengths of the wheat in the homogeneous treatment but decreased them in the placement treatment. Therefore, homogeneously applied urea and DMPP may produce a more uniform nutrient distribution, leading to greater nitrogen retention in the soil and thus accelerating wheat growth.

Flow‐regulated glucose and lipid metabolism in adipose tissue, endothelial cell and hepatocyte cultures in a modular bioreactor

Static cell culture has serious limitations in its ability to represent cellular behaviour within a live organism. In vivo, cells are constantly exposed to the flow of bodily fluids and contact with other cell types. Bioreactors provide the opportunity to study cells in an environment that more closely resembles the in vivo setting because cell cultures can be exposed to dynamic flow in contact with or in proximity to other cell types. In this study we compared the metabolic profile of a dynamic cell culture system to that of a static cell culture in three different cellular phenotypes: adipocytes, endothelial cells and hepatocytes. Albumin, glucose, free fatty acids, glycerol, and lactate were measured over 48 h. We show that all three cell types have increased glucose uptake in the presence of flow; lactate release was also significantly affected. We provide robust evidence that the presence of flow significantly modifies cellular metabolism. While flow provides a more uniform nutrient distribution and increases metabolite turnover, our results indicate that different cell types have specific metabolic responses to flow, suggesting cell-specific flow-regulated activation of metabolite signalling pathways.

Precutting round alfalfa and cornstalk bales decreases time and fuel required for bale breakup in a vertical mixer

Introduction Properly mixing and distributing nutrients throughout a ration can be equally as important as including them in the formulation. Many factors, including forage type, particle length, and mixer type, affect the homogeneity of total mixed rations. Particle size plays an important role in digestion and animal performance and, therefore, is an important consideration from harvest through feeding. An increase in particle size results in a less uniform distribution of nutrients throughout the total mixed ration. Typically, diets with a high proportion of forages have the lowest uniformity of nutrients in individual batches of complete feed.

Determination of Toxic Metals in Petroleum, Cultivated Land and Ore Samples Using Laser-Induced Breakdown Spectroscopy

The growth of the petroleum industry worldwide and the marketing of petroleum products have resulted in the pollution of the environment with heavy metals due to oil spills and leakage from oil tanks and waste oil dumps. The effects of such pollution on the environment, humans, livestock, wildlife, aquatic life, crops, and soil have been enormous. The hazardous waste generated from the petroleum industry poses great dangers to human and animal health, especially since some of the waste is non degradable. For example, it could stay in the soil for many years and pollute precious water resources. The determination of nutrients and trace metal in soil samples is important due to the following reasons: i) soil contaminated with high concentrations of trace metals could pollute underground water resources, ii) within a single farming field, an agricultural producer may encounter non uniform distribution of nutrients (NUDN). Due to NUDN, the field may result in an over or under stress of nutrients (Lal, 1999). This can affect the overall crop yield. Precision farming, where uniform nutrient distribution is managed, is of growing interest among agriculturists and crop producers. In precision farming, management of nutrients allows growers to optimize inputs of nutrients like calcium, phosphorus, nitrogen, sulfur, iron and potassium, on a site-specific basis. By identifying sites where there is deficiency of nutrients in a field, farmers can create management zones and treat these areas with nutrients to enhance the crop yield. Hence the soil analysis is essential for guiding farmers to better identify fertilizer needs within a field. Many researchers are presently investigating optimum soil testing methods for precision agriculture. Efficient testing methods for measuring the concentration of nutrients are required for better estimates of crop yield. The interest in the analysis of ore samples is due to two main factors: i) runoff from mineral processing, and ii) open pit mines dumping tons of toxic waste into nearby water reservoirs, which can directly affect human life, vegetation and livestock in the region. Another significance of ore sample analysis is the determination of ore content quality and the identification of the constituents present in the ore sample. Thus the identification of analytical techniques for detecting elemental composition of ore samples is very important and needs rapid attention. Due to the above-mentioned reasons, a laser induced breakdown spectroscopy (LIBS) spectrometer was tested for the determination of heavy and toxic metals in crude oil residue sample obtained from a local oil producing company. The LIBS system was also tested for analysis of the soil samples collected from tomato cultivated green house soil. LIBS was also used for the chemical elemental analysis of ore samples. In addition to pollution control, information regarding the chemical composition of a substance is also of fundamental importance for numerous tasks during process control and quality assurance in industrial production units. M. A. Gondal (&) Z. H. Yamani Laser Research Laboratory, Physics Department, King Fahd University of Petroleum & Minerals (KFUPM), Box 5047, Dhahran 31261, Saudi Arabia e-mail: magondal@kfupm.edu.sa

The fate of nitrogen in outdoor pig production

There may be a conflict between animal welfare and nitrogen pollution in outdoor pig production. In response to concern about nitrogen being lost to the atmosphere and ground water we quantified spatial variation and temporal dynamics of mineral N, ammonia volatilization, denitrification and nitrate leaching from outdoor pig production at three commercial farms in Denmark. From paddocks containing farrowing sows substantial nitrogen losses were observed, particularly around the feeding areas. Gross ammonia emission rates varied between 0.08 and 1.26 kg N ha–1 d-1 and increased with animal density and N intake. The mean annual loss of ammonia per sow was 4.8 kg N. Denitrification rates averaged 0.52 kg N ha–1 d-1 in autumn following summer grazing with lactating sows, and 0.10 kg N ha–1 d-1 in the following spring. Denitrification losses up to 69 to 114 kg N ha-1 were estimated. Cumulated nitrate leaching during sow grazing and in the following year was 126–276 kg N ha–1. Of the N input in feed to the paddock 44% could be accounted for in piglets, 13% as ammonia volatilization, 8% as denitrification and 16 to 35% as nitrate leaching. The necessary development towards increasing N-use efficiency in outdoor pig production may include changes in management, such as lowering the stock density and reducing the level of dietary N. Also, a more uniform distribution of nutrients in the field may be achieved by manipulating the excretory behavior of the animals

Nutrient excretion by outdoor pigs: a case study of distribution, utilization and potential for environmental impact

Abstract. An increasing number of breeding sows is kept outdoors in Europe. Outdoor pig production has benefits in terms of animalwelfare but may have hidden costs through nutrient losses. We investigated the distribution of nutrients in sow paddocks and the consequence for losses and utilization in the succeeding crop. Significant correlation between soil inorganicNand the distance to feeding sites was observed after the paddocks had been used by lactating sows for 6 months (P&lt;0.01). Near to feeders inorganic N levels became extremely high whereas 30–40m from feeders some patches hadN levels in the topsoil corresponding to the levels in the reference area without sows. In the following spring only a minor part of inorganic N was still present in the top 0–40 cm. Similarly, extractable P and exchangeable K in topsoil were significantly affected by distance to feeders with the highest values close to the feeders (P&lt;0.001). In addition there were significant effects of the distance to huts with increasing nutrient content closer to huts. Although huge variations in dry matter production and nutrient content occurred in the succeeding potato crop, these were only weakly related to the distribution of nutrients (N, P and K) in the previous year, which explained 17%of the total variation in dry matter production. To increase nutrient efficiency in outdoor pig production a uniformdistribution of nutrients should be obtained by manipulating the excretory behaviour of the sows and stocking densities must be adjusted to locally acceptable nutrient surpluses.

Facilitation of plant phosphate acquisition by arbuscular mycotrhizas from enriched soil patches

summaryMycorrhizal contribution to nutrient acquisition from spatially heterogeneous soil was investigated using two‐way comparisons of non‐mycorrhizal and arbuscular mycorrhizal Agropyron desertorum (Fisch. ex Link) Schult. in soil with either a patchy or a uniform nutrient distribution. Double‐labelling allowed a comparison between acquisition of an ion of lower abundance and mobility, phosphate (P), and an ion of higher abundance and mobility, nitrate. As expected, root density increased in enriched‐nutrient patches relative to either unenriched soil or to soil where the same quantity of nutrients was applied to the entire soil volume (uniform‐nutrient treatment). However, the increase of local root density in patches was less for mycorrhizal plants than for non‐mycorrhizal plants. Mycorrhizal infection enhanced plant acquisition of labelled P relatively more in the enriched patches (patchy‐nutrient treatment) than in soil with uniform nutrient distribution, both when expressed on a shoot mass and on a root‐length basis. As expected, plant nitrate acquisition and shoot nitrogen concentration were not significantly affected by either mycorrhizal infection or patterns of soil nutrient distribution. Hence, arbuscular mycorrhizas can enhance root P acquisition and, thus, contribute to plant exploitation of soil P heterogeneity.

Yield of Tomato Irrigated with Recirculating Aquacultural Water

Aquacultural water, which rapidly accumulates organic materials that inhibit fish growth, has considerable potential for hydroponic cultivation of vegetable plants. By recirculating aquacultural water through sand biofilters, it is possible to integrate the two systems whereby both benefit: the vegetables are provided with nutrient-laden water and they control ammonia concentrations in the fish medium. Hybrid tilapia fish [Oreochromis mossambicus (Peters) × O. niloticus (L.)] and tomato (Lycopersicon esculentum Mill.) production were linked in a closed recirculating water system in a polyethylene greenhouse to determine the effect of tank-to-biofilter ratio on tomato yield. The fish were raised in tanks and fed a 32% protein feed. Tomatoes ‘Laura’ and ‘Kewalo’ were grown in sand biofilters during summer 1988 and spring 1989, respectively. Plant spacing was 4 plants/sq yd and each bed was irrigated eight times daily with water from the associated fish tank. Biofilter drainage returned to the tank by gravity. Four tank-to-biofilter (v/v) ratios (1:0.67, 1:1.00, 1:1.50, and 1:2.25) were studied with plant populations proportional to biofilter volume. Each system received equivalent nutrients (even though biofilter size and number of plants differed) and plants received equal water. Biological filtration, aeration, and mineral assimilation of plants maintained water quality for tilapia growth. Yield per plant decreased with increasing biofilter volume but total yield per biofilter increased with increasing biofilter volume. Fruit production per unit feed input and per unit fish biomass increase were highly correlated. From these studies, a balanced high per-plant yield and high total yield were observed with the 1:1.5 tank-to-biofilter ratio. The system operated efficiently so that both fish and fruit production were successful. Research Question Recirculating aquacultural systems accumulate organic materials that inhibit fish growth. This aquacultural water has considerable potential for hydroponic cultivation of vegetable plants. The plants can also aid in controlling nitrate concentrations in the fish medium. The practical application of such integrated fish-vegetable systems is in need of investigation. This study determined how tank-to-biofilter ratio influenced tomato yield per plant and total yield per unit of nutrient input. Literature Summary Hydroponic vegetable production has been shown to be effective in removing organic materials in recirculatory aquacultural systems. Reciprocating biofilters, which alternately flood and drain, provide a uniform distribution of nutrients within the filtration medium. Optimum ratios between feed input rate, standing fish biomass, system water volume, and biofilter volume must be established. Study Description Tilapia fish and tomato production were linked in a closed recirculating system in a polyethylene greenhouse in Raleigh, NC. The fish were raised in tanks and fed a 32% protein feed while the tomatoes (cultivars ‘Laura’ and ‘Kewalo’) were grown in sand biofilters which were alternately flooded and drained with the aquacultural water (Fig. 1). Four tank-to-biofilter (v/v) ratios (1:0.67, 1:1.00, 1:1.50, and 1:2.25) were studied with plant populations proportional to biofilter volume. Applied Question What is the effect of tank-to-biofilter ratio on tomato yield in a recirculatory aquacultural system? Yield per plant decreased with increasing biofilter volume but total yield per biofilter increased with increasing biofilter volume (Fig. 2, 3). Fruit yield also increased with increased unit feed input. To maximize production, it is necessary to determine which ratio gives both a high per-plant yield and a high total yield. From our studies, the 1:1.5 tank-to-biofilter ratio appeared to balance the two appropriately. Figure 1Open in figure viewerPowerPoint Schematic diagram of the integrated aquaculture-olericulture system. Figure 2Open in figure viewerPowerPoint Fruit yield per plant and per biofilter of ‘Laura’ tomato, with the corresponding fish biomass increase, as influenced by tank to biofilter ratio. Figure 3Open in figure viewerPowerPoint Fruit yield per plant and per biofilter of ‘Kewalo’ tomato, with the corresponding fish biomass increase, as influenced by tank to biofilter ratio.

Nutrient Distribution following Wheat‐Residue Dispersal by Combines

AbstractUneven crop residue distribution by a combine may creae non‐uniform nutrient distribution in the field long after harvest. Uniform distribution of nutrients across a field has significant impacts on plant growth, soil sampling, fertilizer efficiency, and nutrient loss to surface and subsurface water. This study was conducted to evaluate nonuniformity of N, P, S, and K distribution across a field following combine harvest of soft white winter wheat (Triticum aestivum L.). Twelve self‐propelled combines were evaluated in 1983 and 10 in 1984. Each combine passed over an 11‐m strip of canvas, divided into 0.94 by 0.91 m segments, which was inserted in a swath cut into the unharvested wheat. Residues deposited on any segment of the canvas were collected and residue distribution and N, P, S, and K content of the residue was determined. Distribution of these four nutrients followed the residue distribution and created cyclic nonuniformity across the landscape. Maximum nonuniformity of nutrient distribution, where 1 = perfect uniformity, ranged from 2.7 to 9.0 for N, 1.9 to 7.7 for S, 2.3 to 9.4 for P, and 1.5 to 6.8 for K. Nutrient distribution was more extreme when wheat was cut closer to the ground. Combine modification to improve chaff distribution significantly improved nutrient distribution.