Soil Physical Quality and Soybean Yield as Affected by Chiseling and Subsoiling of a No-Till Soil

ABSTRACT The concept of soil physical quality (SPQ) is currently under discussion, and an agreement about which soil physical properties should be included in the SPQ characterization has not been reached. The objectives of this study were to evaluate the ability of SPQ indicators based on static and dynamic soil properties to assess the effects of two loosening treatments (chisel plowing to 0.20 m [ChT] and subsoiling to 0.35 m [DL]) on a soil under NT and to compare the performance of static- and dynamic-based SPQ indicators to define soil proper soil conditions for soybean yield. Soil sampling and field determinations were carried out after crop harvest. Soil water retention curve was determined using a tension table, and field infiltration was measured using a tension disc infiltrometer. Most dynamic SPQ indicators (field saturated hydraulic conductivity, K0, effective macroporosity, εma, total connectivity and macroporosity indexes [CwTP and Cwmac]) were affected by the studied treatments, and were greater for DL compared to NT and ChT (K0 values were 2.17, 2.55, and 4.37 cm h-1 for NT, ChT, and DL, respectively). However, static SPQ indicators (calculated from the water retention curve) were not capable of distinguishing effects among treatments. Crop yield was significantly lower for the DL treatment (NT: 2,400 kg ha-1; ChT: 2,358 kg ha-1; and DL: 2,105 kg ha1), in agreement with significantly higher values of the dynamic SPQ indicators, K0, εma, CwTP, and Cwmac, in this treatment. The results support the idea that SPQ indicators based on static properties are not capable of distinguishing tillage effects and predicting crop yield, whereas dynamic SPQ indicators are useful for distinguishing tillage effects and can explain differences in crop yield when used together with information on weather conditions. However, future studies, monitoring years with different weather conditions, would be useful for increasing knowledge on this topic.

Sampling Position under No-Tillage System Affects the Results of Soil Physical Properties

ABSTRACT Understanding the spatial behavior of soil physical properties under no-tillage system (NT) is required for the adoption and maintenance of a sustainable soil management system. The aims of this study were to quantify soil bulk density (BD), porosity in the soil macropore domain (PORp) and in the soil matrix domain (PORm), air capacity in the soil matrix (ACm), field capacity (FC), and soil water storage capacity (FC/TP) in the row (R), interrow (IR), and intermediate position between R and IR (designated IP) in the 0.0-0.10 and 0.10-0.20 m soil layers under NT; and to verify if these soil properties have systematic variation in sampling positions related to rows and interrows of corn. Soil sampling was carried out in transect perpendicular to the corn rows in which 40 sampling points were selected at each position (R, IR, IP) and in each soil layer, obtaining undisturbed samples to determine the aforementioned soil physical properties. The influence of sampling position on systematic variation of soil physical properties was evaluated by spectral analysis. In the 0.0-0.1 m layer, tilling the crop rows at the time of planting led to differences in BD, PORp, ACm, FC and FC/TP only in the R position. In the R position, the FC/TP ratio was considered close to ideal (0.66), indicating good water and air availability at this sampling position. The R position also showed BD values lower than the critical bulk density that restricts root growth, suggesting good soil physical conditions for seed germination and plant establishment. Spectral analysis indicated that there was systematic variation in soil physical properties evaluated in the 0.0-0.1 m layer, except for PORm. These results indicated that the soil physical properties evaluated in the 0.0-0.1 m layer were associated with soil position in the rows and interrows of corn. Thus, proper assessment of soil physical properties under NT must take into consideration the sampling positions and previous location of crop rows and interrows.

Do Rates and Splitting of Phosphogypsum Applications Influence the Soil and Annual Crops in a No-Tillage System?

ABSTRACT Applications of phosphogypsum (PG) provide nutrients to the soil and reduce Al3+ activity, favoring soil fertility and root growth, but allow Mg2+ mobilization through the soil profile, resulting in variations in the PG rate required to achieve the optimum crop yield. This study evaluated the effect of application rates and splitting of PG on soil fertility of a Typic Hapludox, as well as the influence on annual crops under no-tillage. Using a (4 × 3) + 1 factorial structure, the treatments consisted of four PG rates (3, 6, 9, and 12 Mg ha-1) and three split applications (P1 = 100 % in 2009; P2 = 50+50 % in 2009 and 2010; P3 = 33+33+33 % in 2009, 2010 and 2011), plus a control without PG. The soil was sampled six months after the last PG application, in stratified layers to a depth of 0.8 m. Corn, wheat and soybean were sown between November 2011 and December 2012, and leaf samples were collected for analysis when at least 50 % of the plants showed reproductive structures. The application of PG increased Ca2+ concentrations in all sampled soil layers and the soil pH between 0.2 and 0.8 m, and reduced the concentrations of Al3+ in all layers and of Mg2+ to a depth of 0.6 m, without any effect of splitting the applications. The soil Ca/Mg ratio increased linearly to a depth of 0.6 m with the rates and were found to be higher in the 0.0-0.1 m layer of the P2 and P3 treatments than without splitting (P1). Sulfur concentrations increased linearly by application rates to a depth of 0.8 m, decreasing in the order P3>P2>P1 to a depth of 0.4 m and were higher in the treatments P3 and P2 than P1 between 0.4-0.6 m, whereas no differences were observed in the 0.6-0.8 m layer. No effect was recorded for K, P and potential acidity (H+Al). The leaf Ca and S concentration increased, while Mg decreased for all crops treated with PG, and there was no effect of splitting the application. The yield response of corn to PG rates was quadratic, with the maximum technical efficiency achieved at 6.38 Mg ha-1 of PG, while wheat yield increased linearly in a growing season with a drought period. Soybean yield was not affected by the PG rate, and splitting had no effect on the yield of any of the crops. Phosphogypsum improved soil fertility in the profile, however, Mg2+ migrated downwards, regardless of application splitting. Splitting the PG application induced a higher Ca/Mg ratio in the 0.0-0.1 m layer and less S leaching, but did not affect the crop yield. The application rates had no effect on soybean yield, but were beneficial for corn and, especially, for wheat, which was affected by a drought period during growth.

Diallel analysis for grain yield and mineral absorption rate of soybeans grown in acid brazilian savannah soil

High available aluminium and low levels of calcium below the ploughed zone of the soil are limiting factors for agricultural sustainability in the Brazilian Cerrados (Savannahs). The mineral stresses compound with dry spells effect by preventing deep root growth of cultivated plants and causes yield instability. The mode of inheritance for grain yield and mineral absorption ratio of a diallel cross in soybeans [Glycine max (L.) Merrill] grown in high and low Al areas was identified. Differences among the genotypes for grain yield were more evident in the high Al, by grouping tolerant and non-tolerant genotypes for their respective arrays in the hybrids. A large proportion of genetic variance was additive for grain yield and mineral absorption ratio in both environments. High heritability values suggest that soybeans can be improved by crosses among Al-tolerant genotypes, using modified pedigree, early generation and recurrent selection schemes.

Effects of soil water depletion on the water relations in tropical kudzu

Tropical kudzu (Pueraria phaseoloides (Roxb.) Benth., Leguminosae: Faboideae) is native to the humid Southeastern Asia. Tropical kudzu has potential as a cover crop in regions subjected to dryness. The objective of this paper was to evaluate the effect of soil water depletion on leaflet relative water content (RWC), stomatal conductance (g) and temperature (T L) in tropical kudzu. RWC of waterstressed plants dropped from 96 to 78%, following a reduction in SWC from 0.25 to 0.17 g (H2O).g (dry soil)-1.Stomatal conductance of stressed plants decreased from 221 to 98 mmol.m-2.s-1, following the reduction in soil water content (SWC). The day after re-irrigation, g of water stressed plants was 15% lower than g of unstressed plants. Differences in T L between waterstressed and unstressed plants (deltaT L) rose linearly from 0.1 to 2.2ºC following progressive water deficit. RWC and T L of waterstressed plants paralled RWC and T L of unstressed plants the day after reirrigation. The strong decrease in SWC found in this study only induced moderate water stress in tropical kudzu. In addition, tropical kudzu recover rapidly from the induced water stress after the re-irrigation.

Growth and yield of common bean cultivars at two soil phosphorus levels under biological nitrogen fixation

The genotypic differences on growth and yield of common bean (Phaseolus vulgaris L.) in response to P supply were evaluated in a field experiment under biological N2 fixation. Eight cultivars were grown at two levels of applied P (12 and 50 kg ha-1 of P -- P1 and P2 respectively), in randomized block design in factorial arrangement. Vegetative biomass was sampled at three ontogenetic stages. The effects of genotype and phosphorus were significant for most traits, but not the genotype ´ phosphorus interaction. The cultivars presented different patterns of biomass production and nutrient accumulation, particularly on root system. At P1, P accumulation persisted after the beginning of pod filling, and P translocation from roots to shoots was lower. The nodule senescence observed after flowering might have reduced N2 fixation during pod filling. The responses of vegetative growth to the higher P supply did not reflect with the same magnitude on yield, which increased only 6% at P2; hence the harvest index was lower at P2. The cultivars with highest yields also presented lower grain P concentrations. A sub-optimal supply of N could have limited the expression of the yield potential of cultivars, reducing the genotypic variability of responses to P levels.

Bacterial diversity of soil under eucalyptus assessed by 16S rDNA sequencing analysis

Studies on the impact of Eucalyptus spp. on Brazilian soils have focused on soil chemical properties and isolating interesting microbial organisms. Few studies have focused on microbial diversity and ecology in Brazil due to limited coverage of traditional cultivation and isolation methods. Molecular microbial ecology methods based on PCR amplified 16S rDNA have enriched the knowledge of soils microbial biodiversity. The objective of this work was to compare and estimate the bacterial diversity of sympatric communities within soils from two areas, a native forest (NFA) and an eucalyptus arboretum (EAA). PCR primers, whose target soil metagenomic 16S rDNA were used to amplify soil DNA, were cloned using pGEM-T and sequenced to determine bacterial diversity. From the NFA soil 134 clones were analyzed, while 116 clones were analyzed from the EAA soil samples. The sequences were compared with those online at the GenBank. Phylogenetic analyses revealed differences between the soil types and high diversity in both communities. Soil from the Eucalyptus spp. arboretum was found to have a greater bacterial diversity than the soil investigated from the native forest area.

Biomarkers for the assessment of chlorpyrifos effects on earthworms and on soil functional parameters

The objective of this work was to evaluate the effects of chlorpyrifos on earthworms and on soil functional parameters. An integrated laboratory-field study was performed in a wheat field in Argentina, sprayed with chlorpyrifos at two recommended application rates (240 or 960 g ha-1 style='vertical-align:baseline'> a.i.). Laboratory tests included neutral red retention time, comet assay (single cell gel electrophoresis), and avoidance behavior, each using the earthworm Eisenia andrei exposed in soil collected 1 or 14 days after pesticide application, and the bait-lamina test. Field tests assessed organic matter breakdown using the litterbag and bait-lamina assays. Earthworm populations in the field were assessed using formalin application and hand-sorting. The neutral red retention time and comet assays were sensitive biomarkers to the effects of chlorpyrifos on the earthworm E. andrei; however, the earthworm avoidance test was not sufficiently robust to assess these effects. Feeding activity of soil biota, assessed by the bait lamina test, was significantly inhibited by chlorpyrifos after 97 days, but recovered by the 118th day of the test. Litterbag test showed no significant differences in comparison to controls. Earthworm abundance in the field was too low to adequately test the sensitivity of this assessment endpoint.

Leaf mineral composition of grafted eggplant grown in soil infested with Verticillium and root-knot nematodes

The objective of this work was to determine differences in leaf mineral composition between ungrafted and grafted onto (Solanum torvum) eggplant (Solanum melongena), cultivars 'Faselis' and 'Pala', grown in a soil infested with Verticillium dahliae and Meloidogyne incognita, or in a noninfested soil. Grafting increased leaf P and Mn concentrations, and decreased N concentrations, in both soils. Grafting also enhanced leaf Ca concentration of 'Pala', but it did not affect that of 'Faselis' depending on the cropping year. Leaf Mg concentration of grafted plants in infested soil was lower than that of ungrafted ones in noninfested soil. Results showed that, under the same fertilization program, the grafted 'Faselis' plants used the nutrients more efficiently than the 'Pala' ones. Use of S. torvum as a rootstock for 'Faselis' resulted in an effective protection against multiple pathogen infestation. Fertilization may be necessary when grafted 'Faselis' plants are grown in a soil infested with the pathogens, since grafting and infestation generally decrease leaf N, Mg, Ca and Fe concentrations, either by reducing the nutrient concentrations directly or by increasing leaf Mn concentration.

Bioindicators of soil quality in coffee organic cultivation systems

The objective of this work was to assess the effect of different coffee organic cultivation systems on chemical and biological soil characteristics, in different seasons of the year. The following systems were evaluated: coffee intercropped with one (CJ1), two (CJ2) or three (CJ3) pigeon pea (Cajanus cajan) alleys; coffee planted under full sun (CS); area planted with sweet pepper and snap bean in a conventional tillage system (AC); and secondary forest area (FFR). Row spacing in CJ1, CJ2, CJ3 and CS was 2.0x1.0, 2.8x1.0, 3.6x1.0, and 2.8x1.0 m, respectively. Soil samples were collected at 10-cm depth, during the four seasons of the year. The results were subjected to analysis of variance, principal component analysis, and redundancy analysis. There was an increase in edaphic macrofauna, soil basal respiration, and microbial quotient in the summer. Total macrofauna density was greater in CJ2 followed by CJ3, CS, CJ1, AC and FFR; Coleoptera, Formicidae, and Isoptera were the most abundant groups. There are no significant differences among the areas for soil basal respiration, and the metabolic quotient is higher in CJ1, CJ3, and FFR. Microbial biomass carbon and the contents of K, pH, Ca+Mg, and P show greater values in AC.

Root distribution of irrigated grapevine rootstocks in a coarse texture soil of the São Francisco Valley, Brazil

An experiment was carried out to determine the root distribution of four grapevine rootstocks (Salt Creek, Dogridge, Courdec 1613, IAC 572) in a coarse texture soil of a commercial growing area in Petrolina County, São Francisco Valley, Brazil. Rootstocks were grafted to a seedless table grape cv. Festival, and irrigated by microsprinkler. Roots were quantified by the trench wall method aided by digital image analysis. Results indicated that roots reached 1 m depth, but few differences among rootstocks were found. All of them presented at least 90 % of the roots distributed until 0.6 m depth, with a greater root presence in the first 0.4 m. The upper 0.6 m can be taken into account as the effective rooting depth for soil and water management.

GROWTH AND NUTRITION OF CACAO SEEDLINGS INFLUENCED BY ZINC APLICATION IN SOIL

ABSTRACT Levels of Zn in tropical soils profoundly influences growth and nutrition of tree crops. Research was undertaken to assess the effect of soil Zn on growth and nutrition of clonal cacao tree seedlings of PH 16. Three acidic Oxisol soils differing in texture were used with nine doses of Zn (0, 1, 2, 4, 8, 16, 32, 48, and 64 mg dm-3). Rooted clonal seedlings were grown in plastic pot with 11 dm-3 of the soils at varying Zn levels for 240 days. At harvest growth (dry matter mass of leaves, stems, shoots, roots, and total) and nutrient concentrations were determined. The clonal cacao seedlings showed differences for production of dry matter mass and foliar nutrient concentrations for P, K, Ca, Mg, Mn, Fe, Zn, and Cu. There was Zn toxicity in all soils.

Chemigation with benomyl and fluazinam and their fungicidal effects in soil for white mold control on dry beans

The effectiveness of fungicides in controlling white mold (Sclerotinia sclerotiorum) of dry beans (Phaseolus vulgaris) was evaluated when they were applied through irrigation water directly onto the plants or only to the soil. Two field trials were installed in April 1998 and April 1999 in Viçosa, MG. Trials were conducted as a (2 x 3) + 1 factorial: two fungicides x three application modes + one untreated control. The fungicides were benomyl (1.0 kg a.i. ha-1) and fluazinam (0.5 l a.i. ha-1). The three application modes were: (a) by backpack sprayer (667 l ha-1), (b) by garden watering-cans simulating sprinkler irrigation with 35,000 l ha-1 of water, and (c) by garden watering-cans applying water between the rows and near the soil surface in 35,000 l ha-1 of water. In 1998, fungicides were applied at 43 and 54 days after emergence (DAE); in 1999, at 47 and 61 DAE. Both fungicides were similarly effective on white mold control when applied by either chemigation or backpack sprayer, resulting in yields 21% higher than untreated control. Only fluazinam provided disease control when applications were made only in soil. Chemigation provided white mold control equivalent to that of backpack sprayer in terms of incidence, severity and number of diseased pods. Consequently, yield differences between these application methods were not significant.

Test of a microlysimeter for measurement of soil evaporation

Quantifying soil evaporation is required on studies of soil water balance and applications aiming to improve water use efficiency by crops. The performance of a microlysimeter (ML) to measure soil evaporation under irrigation and non-irrigation was evaluated. The MLs were constructed using PVC tubes, with dimensions of 100 mm inner diameter, 150 mm depth and 2.5 mm wall thickness. Four MLs were uniformly distributed on the soil surface of two weighing lysimeters conducted under bare soil, previously installed at Iapar, in Londrina, PR, Brazil. The lysimeters had 1.4 m width, 1.9 m length and 1.3 m depth and were conducted with and without irrigation. Evaporation measurements by MLs (E ML) were compared with measurements by lysimeters (E L) during four different periods in the year. Differences between E ML and E L were small either for low or high atmospheric demand and also for either irrigated or non-irrigated conditions, which indicates that the ML tested here is suitable for measurement of soil evaporation.

Crop coefficient and water consumption of eggplant in no-tillage system and conventional soil preparation

Under organic management in Seropédica-RJ, Brazil, using a weighing lysimeter, the crop coefficients (kc), the maximum evapotranspiration and the productivity of eggplant cultivation under two cropping systems (no tillage with straw plus soil with conventional preparation) were determined. A whole randomized layout with two treatments (no tillage and conventional) and five replicates during 134 days of cultivation were adopted. There were no significant differences in the eggplant cultivation in the two cropping systems, with a maximum commercial productivity obtained from 47.42 Mg ha-1 for the no-tillage system, and 47.91 Mg ha-1 for the conventional tillage. The accumulated ETc was 285.15 and 323.44 mm for the no-tillage and conventional, respectively. The crop coefficients value for the phases: 1 - transplanting, flowering, 2 - flowering-fruiting, 3 - fruit- first harvesting, 4- first harvesting of the final crop cycle was 0.83, 0.77, 0.90 and 0.97 in no-tillage system for the respective phases and for the conventional one 0.81, 1.14, 1.17 and 1.05 for the same steps described above.