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Conventionallymanaged citrus orchards can bemodified to incorporate advanced horticultural practices such as higher plant density and efficient water and fertilizer application known as open hydroponics system (OHS) to increase productivity under Huanglongbing (HLB) endemic conditions. A field studywas conducted from2013 to 2018 to evaluate the effect of an OHS on "Ray Ruby" grapefruit (RR) production under HLB-endemic conditions. We tested a combination of different rootstocks [Sour orange (RR/SO) and US-897 (RR/897)], tree planting densities [standard (STD, 358 trees per ha) and high density staggered (HDS, 953 trees per ha)], fertilization methods (dry granular--dry and fertigation--fert), and irrigation systems (double driplines--DD and microsprinkler--MS), arranged in five treatments: RR/SO_STD_dry_MS, RR/SO_HDS_fert_DD, RR/897_HDS_fert_MS, RR/897_HDS_fert_DD, and RR/SO_HDS_fert_MS. All trees were infected by Candidatus Liberibacter asiaticus five years after planting. Trunk diameter and canopy volume increased over time and were higher under RR/SO_STD_dry_MS compared to other treatments. Total fruit number increased in 2016/17 compared to other seasons; however, 65% of fruit were classified as small (<100 mm). Fruit produced under RR/897_HDS_fert_DD had the highest amount (79%) of adequate size fruit (100-117 mm) compared to other treatments. Fruit yield was similar for both rootstocks planted at HDS using DD andMS fertigation, and 67% higher than the standard treatment (RR/SO_STD_dry_MS). Soluble solid contents (SSC), titratable acidity, and SSC-to-titratable acidity ratio were not affected by the treatments. HDS planting resulted in higher fruit yield, irrespective of rootstock and irrigation system, representing an important advance in grapefruit production. Overall, our results demonstrated that production of grapefruit in high-density using OHS can be used by citrus growers who aim to make the best water and fertilizer management under HLB-endemic conditions. [ABSTRACT FROM AUTHOR]

AbstractLiming is essential for enhancing economic viability and increasing crop production in acidic soil in tropical and subtropical regions. However, continuous limestone application has been associated with cationic micronutrient deficiency, including zinc (Zn). In an experiment under greenhouse conditions using three soils of different textural classes (Typic Alfisol, Typic Oxisol, and Typic Entisol), we evaluated the growth of soybean after fertilization with limestone and Zn. We applied dolomitic limestone at two rates (equivalent to 0 and 5.0 Mg ha−1) and Zn at four rates (0, 5, 10, and 20 mg kg−1), each with four replicates. These three soil types exhibited distinct nutrient availability. Liming significantly altered soil chemical attributes, particularly causing considerable reduction in Zn availability in Typic Alfisol. Furthermore, liming led to a reduction in Zn concentration in soybean leaves and grains in all the three soil types. Grain yield (GY) increased in the presence of liming, and yield was further enhanced with increasing Zn concentrations. Positive effect was also seen on photosynthetic rate (A), stomatal conductance (gs), and leaf N, Ca, and Zn concentrations, except on P concentration. Even with adequate nutrient concentrations and limestone application, sandy soils had a lower GY. [ABSTRACT FROM AUTHOR]

Given the lack of recommendations for the fertilization of Eucalyptus clones in the second production cycle, the effects of fertilizer rates and the number of sprouts per strain in terms of the soil chemical attributes, biometric characteristics, and the concentrations of N and P in the leaves and in the litter of Eucalyptus L’Hér. in the Brazilian Cerrado were evaluated. The experimental design was a randomized block with four replicates, arranged in a 2 × 4 factorial scheme: one or two sprouts per strain; four fertilizer rates (0, 50, 100, or 200% of 200 kg ha−1 of the formula 06-30-06 + 1.5% Cu + 1% Zn) applied immediately after sprout definition. The option of one sprout per strain yielded higher contents of organic matter (K, S, B, and Mn) in the 0.20–0.40-m layer, the leaf chlorophyll index, the diameter at breast height, and the height of the Eucalyptus 44 months after the definition of sprouts. However, N and P leaf concentrations and the wood volume did not differ as a function of the sprout numbers. The fertilizer dosage did not influence the wood volume, even in sandy soil with low fertility. Approximately 86% of the wood volume was obtained from the supply of soil and root nutrient reserves and 14% of this productivity is due to fertilization minerals. The adequate fertilization in the first cycle of the Eucalyptus supplies almost the entire nutritional demand of the forest in the second production cycle. [ABSTRACT FROM AUTHOR]

Calcium water treatment residue (Ca-WTR), an industrial by-product, was found to be effective in decreasing Cu availability in contaminated soils and transport to the environment. In this study, a greenhouse study was conducted to test the ability of Ca-WTR to reduce the toxicity and uptake of Cu by ryegrass (Lolium perenne L.) and lettuce (Lactuca sativa L.) as indicator crop plants in Cu-contaminated sandy soils. Eight weeks growing period was observed in Alfisol and Spodosol amended with different levels of Ca-WTR (5-100 g kg(-1) soil). Plant biomass yields increased with WTR application rates at the low levels (5-20 g kg(-1) for Alfisol, pH 5.45 and 5-50 g kg(-1) for Spodosol, pH 4.66), and decreased at the high levels (>20 g kg(-1) for Alfisol and >50 g kg(-1) for Spodosol). The maximum growth of ryegrass with Ca-WTR was 133% and 149% of the control (without Ca-WTR) for the original Alfisol and Spodosol (without spiked Cu), respectively, while the corresponding values for lettuce was 145% and 206%. Copper concentrations in ryegrass shoots decreased significantly with increasing Ca-WTR application rates. For lettuce, Cu concentration decreased only at high Ca-WTR rates (>50 g kg(-1)). In addition, ryegrass had a greater potential for Cu uptake and translocation than lettuce in both soils., (Copyright © 2011 Elsevier B.V. All rights reserved.)