Adequate Plant Growth Research Articles

Low-cost Light-emitting Diode Lights Reduce Production Cost of Bibb Lettuce Grown in Aquaponic Systems

In temperate climates, aquaponic producers must use artificial lighting; however, purchasing light-emitting diode (LED) grow lights can be cost-prohibitive. Two aquaponic trials evaluated low-cost LED lighting for the growth of bibb lettuce (Lactuca sativa var. capitata). In trial 1, seven low-cost LED lights were screened and compared with a high-end LED grow light. The three best-performing lights in terms of total plant biomass produced (grams) and total plant biomass per unit of electricity (grams per square meter per kilowatt-hour) were more intensively evaluated in trial 2. These lights included Spider Farmer SF-2000 [SPI ($300)], Fluence RAZRx [FLU ($364)], Designers Fountain 6-Light 5000 K LED High Bay Light [DES ($100)], and the control NeoSol DS [NEO ($1400)]. After 17 days, lettuce grown under NEO achieved higher (P ≤ 0.05) total biomass (939 g) than DES (812 g). There were no differences (P > 0.05) in the average individual plant weights in any treatment. Plant production efficiency (grams per square meter per kilowatt-hour) was higher in DES than NEO (P ≤ 0.05) but was not different from SPI and FLU (P > 0.05). Results indicate that low-cost LEDs are a viable option for producers looking to reduce investment costs while maintaining adequate plant growth. To further describe potential cost savings for producers, a partial budget analysis evaluated the net change in profits and benefit/cost ratio (BCR) of the experimental lights. All showed improved economic results compared with the control (NEO). These studies indicate that low-cost LED lights can support similar plant growth, at higher energy efficiencies, with better economic viability than more expensive grow lights.

PRODUCTION AND SOME QUALITY INDICES VARIATION IN CORN - CASE STUDY IN FARM CONDITIONS

The study comparatively analyzed the production results and the values ​​of some quality indices for two corn hybrids, in the specific crop conditions of the Western Plain of Romania. Corn crops was carried out in the area of ​​Grabaț locality, Timis County, Romania. Corn hybrids P9889 and DKC5092 were cultivated, in a non-irrigated system, between 2021 and 2023. Adequate plant growth conditions were ensured through crop technology. In the case of the P9889 hybrid, the productions were 8500 kg/ha (2021), 5350 kg/ha (2022), and 11000 kg/ha (2023). In the case of the DKC5092 hybrid, the productions were 7900 kg/ha (2021), 5800 kg/ha (2022) and 10800 kg/ha (2023). Based on mean grains samples, the crude protein content (CP) showed values ​​between 8.5% (year 2021) and 10.05% (year 2023); the starch content (ST) presented values ​​between 54.09% (year 2021) and 59.04% (year 2023); the crude cellulose content (crude fibers, CF) presented values ​​between 1.99% (year 2021) and 2.25% (year 2023); the proportion of broken grains (BG) showed values ​​between 0.98 (year 2023) and 1.3% (year 2022), with an mean value BG = 1.10%. A very strong positive correlation was recorded between CP and M (r = 0.955), between ST and M (r = 0.900), and between ST and CP (r = 0.989). Very strong negative correlation was recorded between Y and BG (r = - 0.926). A strong, positive correlation was recorded between CF and Y (r = 0.834), and between CF and M (r = 0.865). According to PCA, PC1 explained 60.307% of variance, and PC2 explained 39.693% of variance. The decrease in production in 2022 (extremely dry year), compared to the mean value, was DY = -2933.33 kg/ha for the P9889 hybrid, respectively DY = -2366.67 kg/ha for the DKC5092 hybrid. From the analysis of the obtained values, the hybrid P9889 recorded a greater decrease in production (difference of 566.66 kg/ha) compared to the hybrid DKC5092, under the conditions of 2022, specific to the study conditions.

Struvite as a Sustainable Fertilizer in Mediterranean Soils

Recycled sources of phosphorus (P) and nitrogen (N), such as struvite extracted from wastewater, have the potential to substitute conventional manufactured fertilizers and mitigate environmental problems such as water eutrophication or the depletion of non-renewable resources. This study aimed to evaluate the potential of struvite as a nitrogenous and phosphate fertilizer in the Spanish Mediterranean region. Two experiments were carried out using struvite recovered from sewage sludge and different representative soils from the area. Since knowing the rates at which their nutrients are released is key for efficient use, experiment I determined the struvite N-releasing rate for 16 weeks. Experiment II studied the effect of different struvite doses (50, 100, 200 kg P2O5 ha−1) on crop growth compared to superphosphate + ammonium nitrate. The results indicated N-releasing rates that fall in line with a slow-release fertilizer. More than 20% of applied struvite-N was unavailable for plants or in the longer term, which suggests struvite fractionation as the most efficient application method. Struvite showed similar fertilization capacity, which was even better at some points, than conventional mineral fertilization, plus adequate plant growth and good nutrient concentration at the 50 kg P2O5 ha−1 dose. Based on this study, struvite can be considered an interesting and effective option for sustainable fertilization in the Mediterranean region.

Carbon and Nitrogen Mineralisation in Soils and Nutrient Efficiency of Digestates from Fruit and Vegetable Wastes

A significant amount of fruit and vegetable wastes is generated annually in markets, supermarkets, restaurants and households. Anaerobic digestion allows their appropriate management and helps to complete the cycle of the circular economy as it converts wastes into resources: biogas, a renewable source of energy, and digestate, rich in nutrients of interest for agriculture. The aim of this study was to define the agronomic value of digestate from fruit and vegetable wastes. Two digestates from fruit and vegetable residues were used in incubation experiments for C and N mineralisation in the soil, and in a pot experiment with crops (cardoon and maize), to calculate their fertiliser potential in comparison with a mineral fertiliser. The digestate quickly mineralised in the soil and nitrification processes led to fast formation of NO3−-N. However, increasing the digestate application rate enhanced N-immobilisation and reduced N-mineralisation in the soil. The addition of digestates to the soil resulted in adequate plant growth and nutrient composition, without any negative effects on the plants or soil. However, special attention should be paid to the salt accumulation in the soil for long-term digestate application. The nutrient recovery efficiency indicated that digestate could replace mineral fertiliser completely in cardoon crops and partially (44.5–82.6%) for maize, with an associated economic benefit. The salinity of the digestates limits their quality and their agricultural use to salt-sensitive crops should be limited.

Determination of age-dependent endogenous indole-3 acetic acid (IAA) level in different organs of tomato plants

Indole-3-acetic acid (IAA), a phytohormone, is a crucial modulator of plant growth and development. As increased levels of endogenous IAA is responsible for inhibitory effects on plants, knowing its concentration would be helpful for controlling exogenous IAA input. An optimum endogenous IAA level is required for proper growth and development of plant with good health status. Hence, in this study, we have detected and measured IAA present in tomato root, shoot, leaves and fruits at two different ages (25 days and 50 days) by Reversed-Phase High Performance Liquid Chromatography (RP-HPLC), a suitable chromatographic method for separating molecules based on hydrophobicity. We observed that the endogenous level of IAA was significantly higher in roots, shoots, leaves and fruits at 50-days old plant compared to 25-days old mature plant (p-value <0.01). These results suggested that the IAA level may increase with the increase of the age of tomato plants. The tomato plants showed good vigor with IAA range 0.3-3.0 µg/g.F.W (25 days) and 3.4-7.5 µg/g.F.W (50 days) of age, respectively, implying that IAA might be used as a possible plant health indicator. Further study is needed to manipulate the IAA concentration for adequate plant growth and development.

Effect of Substrate of Carnauba Residue with Humic Substances on Seedling Production of Papaya Cultivar ‘Golden’

ABSTRACT In the search for sustainable alternatives in the production of seedlings, the use of substrates from residues has been highlighted and fertilizations can be made to ensure adequate plant growth. Our study aimed to evaluate seedling production of papaya on substrates based on the carnauba residue under doses of humic substances. The experiment consisted of humic substances (HS): 0; 12.5; 25 and 50 g L−1 and substrates based on carnauba bagana (CB): 0% CB (soil); 50% CB + 50% soil and 100% CB, with four replicates. At 60 days after sowing, leaf area (FA) was evaluated; plant height (AP); stem diameter (DC); root length (CR); root volume (VR); dry matter of the aerial part (DMAP), dry matter of the root system (DMRS); and the Dickson Quality Score (DQI). By analyzing the papaya seedlings, a significant effect was observed for all variables studied in relation to the carnauba residue (CR) factor, different from the dose factor of humic substances (HS), which did not present significant difference for RV, DMAP, DMRS, and DQI. However, significant interaction between carnauba residue and humic substance was observed for LA, PH, SD, RL, RV, and DQI. The combination of 100% carnauba residue as a substrate and 12.5 g L−1 humic substances was more effectiveness for the production of papaya seedlings.

Effects of compost, biochar and ash mixed in till soil cover of mine tailings on plant growth and bioaccumulation of elements: A growing test in a greenhouse

Mine closures necessitate vegetation restoration to cover tailings fields and reduce environmental risks. Sole use of forest soil as growth medium provides only low fertility and slow plant growth especially in the harsh boreal climate conditions. This preliminary study examines the feasibility of recyclable waste materials added to forest till soil for improving vegetation success on reclaimed mine tailings. One compost type, three biochar types (Bc1–3) and two ash types (Ash1-2) were studied for physical and chemical properties as well as their effects on the growth and element accumulation of timothy (Phleum pratense L.), white clover (Trifolium repens L.) and Scots pine (Pinus sylvestris L.) during one growing period in a greenhouse. Oxidized surface tailings soil and Ash2 were the finest media components while compost and Ash1 were the coarsest. Tailings soil also had the highest salt contents and electrical conductivity, while in till soil they were at the lowest levels. Timothy and white clover germinated well in moist pure tailings soil but grew poorest in it. White clover grew poorly also in pure till soil. Best biomass growth was in the mixture of till, compost and Bc2 (from sewage sludge and woodchips). Planted pine seedlings grew relatively well in all media during the first growing season but Ash1 (from wood and peat) tended to promote height growth and pure till soil root biomass. In media containing Ash1, pine tissues accumulated B, Ca, Mg, K, Na and S. Elevated As content in tailings soil accumulated in plant shoot tissues slightly; only in the old needles of pine were As levels elevated. The results suggest that till and tailings media with compost added as a nitrogen source can promote adequate plant growth during initial growing seasons. Suitable types of biochar and ash amendments can further expedite plant establishment.

Effect of K and Zn Application on Biometric and Physiological Parameters of Different Maize Genotypes

Potassium (K) and zinc (Zn) are mineral nutrients required for adequate plant growth, enzyme activation, water retention and photosynthetic activities. However, Pakistani soils are alkaline and have serious problems regarding Zn deficiency. The current study aims at finding the nutrient–nutrient interaction of K and Zn to affect maize plants’ (i) physiological processes and (ii) productivity. For this purpose, a pot experiment was conducted at the research area of the Department of Soil Science, Faculty of Agricultural Science and Technology, Bahauddin Zakariya University, Multan. Two maize genotypes, DK-6142 (hybrid) and Neelam (non-hybrid), were used with three K fertilizer doses, i.e., 0, 60 and 100 kg ha−1 in all possible combinations with three Zn fertilizer doses, i.e., 0, 16 and 24 kg ha−1. The treatments were replicated under a completely randomized block design. The results elucidated that the combined application of K and Zn with K60 + Zn16 treatment significantly increased agronomic, productive, and physiological attributes. It has improved fresh biomass (89%), dry biomass (94%), membrane stability index (142%), relative water content (200%) and chlorophyll contents (191%) as compared to the control. Moreover, the mineral uptake of K and Zn was significantly improved with their maximum fertilization rate in hybrid genotype compared to non-hybrid and CK.

Evaluation of engineered soils for bioretention areas containing dredged Illinois River sand, compost, biosolids, and pyrolyzed biosolids

AbstractDredged Illinois River sand is nutrient poor and has low cation exchange capacity. Engineering this soil by adding amendments to increase nutrient retention may help sustain plant growth and absorb contaminants when the sand is used in bioslopes, bioswales, and rain gardens. The objectives of this study were to compare the physical and chemical properties of engineered soils derived from dredged Illinois River sand combined with mixtures of a locally produced compost, dried Class B biosolids from the Greater Peoria Sanitary District (GPSD), and pyrolyzed GPSD biosolids, and to study their effect on the growth of a grass mixture designed for chronically wet areas, such as bioslopes and/or bioswales along Illinois Department of Transportation (IDOT) highways. Dry and wet bulk densities of the soil mixtures increased with increasing levels of both biosolids and pyrolyzed biosolids. Soils containing higher levels of compost were linked to higher CEC, soluble salts, porosity, and soil moisture. Shoot and root lengths, and fresh and dry tissue mass were highest in mixtures containing the higher compost levels. These results indicate that the addition of compost to Illinois River sand may be required for adequate grass growth in these engineered soils saturated with water. The use of either biosolids or pyrolyzed biosolids as nutrient sources may need to be supplemented with compost for adequate plant growth.

Fertilizer Recommendations for Sugarcane Pre-sprouted Seedling Production in Ebb-and-Flow Subirrigation Benches

Ebb-and-flow subirrigation can save water and nutrients by reusing fertilizer solution (FS). Since there is no leaching and salts tend to accumulate over time in the growing media, nutrient concentrations should be lower than applied by other irrigation systems. However, fertilizer requirements for subirrigated sugarcane (Saccharum species hybrid) pre-sprouted seedlings (SPSS) are not yet available. Our objective was to evaluate two FS concentrations to produce SPSS in an ebb-and-flow system: 33% and 67% of the recommended concentrations for seedlings produced using overhead irrigation. We tested three cultivars (IACSP95-5000, IACSP95-5094 and IAC91-1099) in terms of crop growth and macronutrient content of stems and leaves. There was no effect of FS concentrations on 1st ligule height, diameter, and dry weight. Irrigation with both FS concentrations resulted in seedlings with adequate nutritional status. Substrate electrical conductivity (EC) increased for treatment irrigated with FS 67%, indicating excessive fertilization. For FS 33%, substrate EC remained stable. FS with concentration of 33% can be used to produce SPSS in ebb-and-flow benches, resulting in adequate plant growth and fertilizer savings.

Effect of Microalgal Extracts from Chlorella vulgaris and Scenedesmus quadricauda on Germination of Beta vulgaris Seeds.

Sugar beet (Beta vulgaris subsp. vulgaris) is a commercially important biennial root crop, providing about 20% of the world’s annual sugar production. Seed quality is crucial for adequate plant growth and production. The productivity of sugar beet is often limited by heterogeneous germination in the field. In order to improve the sugar beet germination process, the effect of different concentrations of microalgal extracts from Chlorella vulgaris or Scenedesmus quadricauda was investigated by calculating several indices useful to evaluate the germination performance. Moreover, root morphological analysis was performed by using WinRHIZO software. B. vulgaris seeds were soaked with five different concentrations (from 0.1 to 10 mg Corg/L) of the microalgal extracts, considering the amount of organic carbon (Corg) in each extract. Our results show that these microalgal extracts exert a positive effect on sugar beet germination, by increasing efficiency and regularity of this critical process for B. vulgaris seeds. The best results, in terms of germination indices as well as root morphological traits, were reached by using C. vulgaris extract at the concentrations C2 (1 mg Corg/L) and C3 (2 mg Corg/L).

Florida Citrus Nursery Trends and Strategies to Enhance Production of Field-Transplant Ready Citrus Plants

The Florida citrus industry is going through major changes and considerable replanting. Many growers are planting varieties, especially rootstocks, that are potentially productive under Huanglongbing (HLB; Candidatus Liberibacter asiaticus) prevalent conditions. However, the high demand for new plant material has put tremendous pressure on citrus nurseries and has created a bottleneck in production. Often it can take more than one year to produce field-transplant ready plants in nurseries; therefore, there is a critical need to accelerate plant production. This three-part study was conducted with the following objectives: (1) determine citrus nursery trends; (2) evaluate use of compost for rootstock germination; and, (3) evaluate use of compost for rootstock seedling growth. According to the nursery survey, rootstock seed germination and seedling growth were the most time-consuming, taking 6–8 months. Moreover, it was apparent from the survey results that 44% of the citrus nurseries were experimenting with potting mixes to achieve adequate plant growth and quality. Our greenhouse study demonstrated successful use of yard waste compost in place of peat moss in a potting mix. With use of 37% to 50% of compost in the potting mix, the overall germination rate and mean emergence time were improved to 70% in less than four weeks for US-897 rootstock as compared to no compost in the potting mix. In addition, 37% to 50% compost resulted in higher biomass accumulation in seedlings. When seedlings of rootstocks C-32 and Flying Dragon were grown with 37% to 50% compost, the growth rate and, therefore, percentage of successful budding were significantly increased as compared to no compost. In addition, substrate analysis indicated that a high compost potting media was rich in mineral nutrients, hence the use of fertilizer in nurseries could be minimized. Altogether, use of compost in place of peat moss seems promising and could accelerate germination and growth of rootstocks, reducing the production time as well as cost.

Does Irrigated Corn Require Multiple Applications of Sulfur?

Sulfur is applied to irrigated corn (Zea mays L.) grown on sandy soils. The objective of this study was to evaluate the sprinkler‐irrigated corn response to S. Treatments were a factorial combination of 0, 14, 28, and 42 kg S ha−1 as (NH4)2SO4 applied on the soil surface at four locations at planting and in season (V5). Tissue samples were collected at V8 and R2 and evaluated along with corn grain yield and soil pore water SO42––S concentration measured at 60 cm with suction tube lysimeters. Application of S increased V8 plant mass, V8 whole plant S concentration and S uptake, and R2 leaf S concentration but did not increase corn grain yield. Decreased V8 plant mass was a result of S deficiency and was only corrected when some S was applied at planting. A total of 28 kg S ha−1 was sufficient to ensure adequate plant growth and S uptake whether S was applied at planting, in‐season, or as a combination of the two timings. Concentrations of S were elevated in soil pore water from at planting and in‐season S application indicating a portion of the S applied were still available for most—and at the end of—the growing season. Sulfur fertilizer is crucial early in the growing season for irrigated corn to ensure optimal corn growth. Rate of application is more important than time of S application in irrigated corn production. Incidental applications of S may reduce the need of S fertilizer for irrigated corn.Core Ideas Application of sulfur at planting is required to maximize early irrigated corn plant mass. Delaying sulfur application to the V5 growth stage results in luxury uptake of S in corn. Rate of sulfur applied is of greater importance than timing and number of applications. Sulfur applied at planting will not fully leach from the root zone the year of application. Sulfur fertilizer may not be required to achieve maximum grain yield for irrigated corn.

Combination of soil organic and inorganic amendments helps plants overcome trace element induced oxidative stress and allows phytostabilisation

Trace element (TE)-contaminated soils require the improvement of their physico-chemical properties in order to allow their restoration through phytostabilization technologies. This study aimed to determine the usefulness of oxidative stress related parameters to validate the suitability of two different combinations of organic (solid fraction of pig slurry) and inorganic (paper mill sludge or a commercial red mud derivative) amendments for the phytostabilization of an acidic (4.2) TE-contaminated mine soil from SE Spain. Two wild species (Silybum marianum and Piptatherum miliaceum) were greenhouse cultivated and the development of the plants, their ionome, and oxidative stress related parameters were determined. Both amendment combinations increased significantly soil pH (to 5–6) and soil/pore water total organic C and total N concentrations, allowing an adequate plant growth and development (plants did not grow in untreated soils). The combination of amendments significantly reduced metal availability and showed to be effective (specially the one including the red mud derivative) in limiting shoot TE concentrations, which were all within common ranges (exclusion based tolerance of these species). Both protein carbonylation and lipid peroxidation were significantly higher in S. marianum plants from phytostabilized soils than in those from non-contaminated soils, which confirms the oxidative stress these plants suffer despite their satisfactory growth in the treated soils. P. miliaceum plants showed no differences between phytostabilized and non-contaminated soils. Therefore, the combination of amendments and TE-tolerant autochthonous species would be a suitable option for the phytostabilisation of soils contaminated by mining activities, reducing TE solubility and allowing an adequate plant growth.

Diversity of microorganisms associated to Ananas spp. from natural environment, cultivated and ex situ conservation areas

Brazil is among the world's largest fruit producers, with emphasis on pineapples [Ananas comosus var. comosus (L.) Merril]. Although it is believed that Ananas spp. maintains relationships with a large range of phytopathogenic or beneficial microorganisms, studies of the microbial diversity associated with pineapple plants are still scarce. Therefore, the present work aimed to quantify and compare the diversity of culturable microorganisms considered in the literature as beneficial, existing in the rhizospheric soil and in internal tissues of Ananas spp. from three different environments: natural populations, commercial cultivation field and ex situ conservation area - Pineapple Germplasm Bank (Pineapple GB). Culture-dependent methods were applied to the microbial communities associated with Ananas spp., as well as molecular techniques based on BOX and ERIC markers for characterization of the samples and its fractions. These techniques allowed the grouping of isolates from different environments and fractions, such as those from soil, root and stem, in the same cluster, implying that there is correspondence in the distribution of beneficial microbiota (functional groups) from the soil to the aerial parts of plants. Furthermore, correlation analyses indicated the association of certain functional groups with the samples and that the plants are always requiring the same groups of microorganisms as in a certain network for sustaining adequate plant growth. The results enable a series of possible applications to this important crop species.

Effect of addition of sewage sludge and coal sludge on bioavailability of selected metals in the waste from the zinc and lead industry

This study evaluated the content of bioavailable forms of selected heavy metals present in the waste from Zn and Pb processing that can potentially have an effect on the observed difficulties in reclamation of landfills with this waste. The particular focus of the study was on iron because its potential excess or deficiency may be one of the causes of the failure in biological reclamation. The study confirmed that despite high content of total iron in waste (mean value of 200.975gkg−1), this metal is present in the forms not available to plants (mean: 0.00009gkg−1). The study attempted to increase its potential bioavailability through preparation of the mixtures of this waste with additions in the form of sewage sludge and coal sludge in different proportions. Combination of waste with 10% of coal sludge and sewage sludge using the contents of 10%, 20% and 30% increased the amounts of bioavailable iron forms to the level defined as sufficient for adequate plant growth. The Lepidum sativum test was used to evaluate phytotoxicity of waste and the mixtures prepared based on this waste. The results did not show unambiguously that the presence of heavy metals in the waste had a negative effect on the growth of test plant roots.

Sistemas radicales de cultivos: extensión, distribución y crecimiento

The roots are the plant organs responsible for water and nutrient absorption which are needed for adequate plant growth. Therefore, it is important to know both the extent and distribution of the root system into the soil since it determines the ability of the plant for mining soil resources, especially in poor soils or soils with low nutrient or water availability. The present work describes the root system of different crops and their relationships with the shoot, and how it determines the efficiency for nutrient uptake. On the other side, we review some morphological adaptations of the root system that improve the absorption of nutrients. This work also describes how the renewal of the root system occurs in a growing season and how it changes or adapts depending on environmental stress factors affecting the plants.

Tolerance of upland rice cultivars to aluminum and acidic pH

ABSTRACT Although the upland rice has been known by its moderate tolerance to aluminum, the presence of exchangeable aluminum in acidic soils may inhibit and compromise the adequate plant growth. However, there are few reports detailing modern cultivars used by Brazilian farmers with respect to their susceptibility to aluminum toxicity. This study aimed to characterize the cultivars currently used in the upland rice production with respect to their tolerance to aluminum and their growth under low pH conditions without aluminum. The treatments were arranged in a randomized block design, in a 2 x 9 factorial scheme: presence and absence of aluminum in the nutrient solution and nine upland rice cultivars (BRS Monarca, BRS Pepita, BRS Bonança, BRS Primavera, BRS Sertaneja, Maravilha, IAC 202, ANCambará and ANa7007), with four replicates. Based on the distribution of upland rice cultivars in quartiles, they were divided into two groups; aluminum-tolerant group: BRS Pepita, BRS Primavera and ANa7007; and aluminum-susceptible group: BRS Monarca, BRS Bonança, BRS Sertaneja, Maravilha, IAC 202 and ANCambará.

Soy-composite Biocontainers Allow for Reduced Fertilizer Inputs during Container-crop Production

Bioplastics and bioplastic composites are a group of emerging sustainable materials that exhibit favorable characteristics for use in horticulture-production containers. Biocontainers made from composite materials of soy [Glycine max (L.) Merr.] bioplastic and poly(lactic) acid (PLA) have been shown to release nitrogen (N) at a rate suitable for supporting plant growth. We hypothesized that fertilizer applications can be reduced while maintaining adequate nutrition levels for plant production when using soy-based containers. To test this hypothesis and quantify potential reduction of fertilizer, we grew marigold ‘Honeycomb’ (Tagetes patula L.) in five prototypes of soy-composite biocontainers [soy bioplastic compounded with PLA or polyhydroxyalkanoates (PHA)] and a petroleum-plastic (polypropylene) control container with five fertilizer treatments supplying 1) 60N‒4P‒49K; 2) 75N‒5P‒61K; 3) 105N‒7P‒85K; 4) 150N‒10P‒122K; or 5) 300N‒20P‒244K mg. At harvest, plants grown in all soy‒PLA composite biocontainers and protein + PLA biocontainers had higher concentrations and contents of N and P compared with plants grown in petroleum-plastic containers across all fertilizer treatments. Shoot K concentrations were highest for plants grown in all soy‒PLA and soy‒PHA biocontainers compared with plants grown in petroleum-plastic containers across all fertilizer treatments, whereas shoot K concentrations in plants grown in protein + PLA biocontainers were equal to or lower than plants in petroleum-plastic containers. Total plant dry weight was greater for plants grown in biocontainers made of 50% soy‒50% PLA and protein + PLA than for plants grown in control containers across all fertilizer treatments except at the highest rate of fertilizer in which plants received 300N‒20P‒244K mg. Our results support the hypothesis that fertilizer inputs can be reduced when using soy-composite biocontainers. Biocontainers made with equal parts soy bioplastic and PLA showed strong potential for achieving adequate plant growth with reduced fertilizer input. Our results demonstrate that fertilizer can be reduced by as much as 80% when growing marigold in containers made of 50% soy‒50% PLA for 6 weeks.

English

The no-tillage technique has been expanding in the Brazilian Cerrado (savanna), but due to the rapid decomposition of residues and few options for profitable rotation crops, soil compaction can be a problem, seriously reducing water availability to plants. Determination of the least limiting water range (LLWR) is a sensitive method to assess the current soil compaction state, although it is operationally and economically beyond the reach of most farmers. Therefore, the aim of this study was to determine the LLWR of a highly loamy typic Oxisol (dystrophic red Latosol) and to evaluate the possibility of estimating it by using the relative bulk density (RBD), determined based on the soil compaction curve, which in comparison is a relatively fast and inexpensive method. The results showed that RBD was strongly correlated with LLWR, with coefficient of determination between 0.69 and 0.95, besides having low mean standard estimation error of at most 0.016 m3 m-3 (P < 0.0001), making measurement of the RBD satisfactory, to estimate the LLWR. Besides this, the RBD values corresponding to BDcritical, that is, when LLWR = 0, were very near the RBD value (≈ 0.90), taken as the upper limit of physical quality for adequate plant growth. Therefore, because of the high cost and laboratory time necessary to determine the LLWR for each type of soil, a viable alternative is to use the reference value or maximum acceptable RBD limit value of 0.90 for management of soil compaction, obtained through geostatistical analyses, to ascertain the variability in the cultivated areas where RBD ≥ 0.90. In short, it is technically and economically feasible to estimate the LLWR based on the RBD.   Key words: Soil compaction curve, proctor normal test without sample reuse, no-till farming in Mato Grosso, Midwest region of Brazil.