Exploring six reduced irrigation options under water shortage for ‘Golden Smoothee’ apple: Responses of yield components over three years

Water for irrigation is in short supply worldwide, therefore reduced irrigation options will have to be explored. We did this for ‘Golden Smoothee’ apple over the growing seasons of 2003-2005 at the IRTA-Estaciò Experimental de Lleida (41°37′ N; 0° 52′ E; 260 m a.s.l.), Catalonia, Spain. This region has a temperate climate with winter-dominant rainfall. Averages of annual rainfall and reference evapotranspiration over 2000-2009 were, respectively, 371 and 1023 mm. The treatments were: Control (C), receiving full irrigation; spring irrigation (SI), where at the budbreak 80 mm of water was applied followed by watering so that the total water applied in the season was either at 33% of C (SI-33) or at 50% of C (SI-50); and deficit irrigation (DI), where trees were irrigated either with 33% of C (DI-33) or with 50% of C (DI-50). Water in DI was applied either through one dripper per tree (DI-33-1d and DI-50-1d) or through two drippers per tree (DI-33-2d and DI-50-2d). Trees showed biennial bearing with 2004 being an ‘off-year’ when treatment effects on yield were largely masked by the higher values of stem water potential associated with lower crop loads. SI-50 and SI-33 performed poorly and cannot be recommended. For each of the DI treatments, the one-dripper version increased fresh market yield and fruit size. For example, although DI-50 performed better than DI-33, DI-33-1d was similar in performance to DI-50-2d. Under water shortage, we recommend whole-season application of DI-50-1d and DI-33-1d depending on the availability of water supply.     

Assessment of tree species richness as a surrogate for macrofungal species richness

Attempts to understand and conserve biodiversity are hampered by a lack of information about many taxonomic groups, particularly those groups that are the most species rich. Although fungi are ubiquitous and play an important role in decomposition, nutrient cycling and nutrient uptake, little is known about fungal diversity, as fungi are usually cryptic and ephemeral. Based on a meta-analysis of macrofungal diversity studies, we show that tree diversity is a promising surrogate for macrofungal diversity at large spatial scales. We present evidence that trees species richness can be used to predict macrofungal species richness and that on the global scale, the distribution of individual tree and macrofungal species notably differs. Additionally our findings provide support for the use of “ratio estimates” to estimate fungal species richness.     

Evaluation of partial root-zone drying for potential field use as a deficit irrigation technique in commercial vineyards according to two different pipeline layouts

The use of partial root-drying (PRD) irrigation implies doubling pipelines instead of using a conventional single pipeline. However, pipelines can be spaced a short distance apart (e.g. 1 m) along the vine row (“D” layout) or joined with cable ties and laid as a single pipeline (“S” layout). Pipelines in “S” configuration are laid under the vine row, and in “D” at both sides of the vine row. These two different layouts can change the wetted soil zone and affect grapevine response to irrigation. The focus of this study was therefore on establishing the role of pipeline layout in vine-grape (cv. ‘Tempranillo’) response under semi-arid conditions in which PRD is managed as a deficit irrigation technique. Six irrigation treatments were applied, which resulted from the combination of Control (C, full irrigation), PRD and seasonal sustained deficit irrigation (SSDI), and “S” and “D” pipeline layouts. SSDI and PRD were irrigated to 50% C throughout the irrigation season, and C irrigation was scheduled according to a crop water balance technique. Midday stem water potential (Ψ_stem) and leaf conductance (g_l) indicated that, on the whole, PRD treatments had a slightly higher water status than SSDI treatments, but a substantially lower status than C treatments. Use of the “D” pipeline layout significantly reduced Ψ_stem in both PRD and SSDI treatments and in some instances for Control conditions, too. Berry yield, vine intercepted radiation, leaf abscisic acid (ABA) and g_l were highly correlated with Ψ_stem. Differences in water status between PRD-S and SSDI-S, according to a sub-surface irrigation test, seemed to be more related to changes in soil evaporation losses and irrigation efficiency than to any intrinsic PRD effect. PRD-S accounted for water savings equivalent to 10% according to the ratio between applied water and grape production for the SSDI-S treatment, whereas PRD-D berry yield was not significantly different from that associated with the SSDI-S treatment. In conclusion, under the growing conditions of this experiment, PRD-S offered the possibility of slightly improving water conservation when irrigation was applied to the soil surface.     

A comparative study of apple and pear tree water consumption measured with two weighing lysimeters

A five-year experiment (2002–2006) was conducted to determine apple (cv ‘Golden Smoothee’) and pear (cv ‘Conference’) crop coefficients (Kc) using two large weighing lysimeters. Daily reference evapotranspiration (ETo) and crop evapotranspiration (ETc) were evaluated. Midday canopy light interception of both crops planted in hedgerows, 4 × 1.6 m, was determined on a weekly basis from bud-break until leaf fall from year 2002 (fourth after planting) to year 2006 of both plantations. Relationships between canopy light interception and calculated Kc (ETc/ETo) were evaluated from bud-break until harvest. There were differences in Kc values between apple and pear trees. When daily Kc values from bud-break until harvest were adjusted to hyperbolic functions each year, adjusted curves for pear trees were very similar regardless of year (maximum Kc around 1.0). In apple trees, the maximum values of Kc increased over time, from 0.49 in 2002 to 1.04 in 2006. Midday light interception in both apple and pear trees increased during the 5 years of experiment from 29.0 to 45.6% in apples and from 27.5 to 41.6% in pears in midsummer. Although there was a significant positive correlation between midday canopy light interception and Kc in apple and pear trees, in different times within a specific year, these relationships were different between crops. While the apple data fitted into the same equation regardless of the year, different equations were needed to fit the pear data in different years. This discrepancy may have been related to differences in the canopy properties between apple and pear trees. Pear canopies had higher porosity than apple canopies and thus improved light penetration. Apple trees were more vigorous and produced taller and denser canopies. Pear Kc values were greatly influenced by the evaporative demands of different years and consequently differences in midday canopy light interception did not adequately reflect the differences in Kc across the two species.     

A first-order analysis of the heat wave in the soil

On the basis of a realistic distribution of the net radiative flux density (composed of a half sinusoid for the shortwave contribution plus a term dependent on the soil surface temperature for the longwave contribution), the solutions regarding the propagation of both the diurnal thermal wave and the heat flux density in the soil are analyzed. The more relevant differences from the analytical solutions obtained under the classical hypothesis of pure sinusoidal forcing waves on the boundary are therefore pointed out.     

Development and characterisation of a <Emphasis Type="Italic">Brassica carinata</Emphasis> inbred line incorporating genes for low glucosinolate content from <Emphasis Type="Italic">B. juncea</Emphasis>

The presence of high levels of sinigrin in the seeds represents a serious constraint for the commercial utilisation of Ethiopian mustard (Brassica carinata A. Braun) meal. The objective of this research was the introgression of genes for low glucosinolate content from B. juncea into B. carinata. BC₁F₁ seed from crosses between double zero B. juncea line Heera and B. carinata line N2-142 was produced. Simultaneous selection for B. carinata phenotype and low glucosinolate content was conducted from BC₁F₂ to BC₁F₄ plant generations. Forty-three BC₁F₄ derived lines were selected and subject to a detailed phenotypic and molecular evaluation to identify lines with low glucosinolate content and genetic proximity to B. carinata. Sixteen phenotypic traits and 80 SSR markers were used. Eight BC₁F₄ derived lines were very close to N2-142 both at the phenotypic and molecular level. Three of them, with average glucosinolate contents from 52 to 61 micromoles g⁻¹, compared to 35 micromoles g⁻¹ for Heera and 86 micromoles g⁻¹ for N2-142, were selected and evaluated in two additional environments, resulting in average glucosinolate contents from 43 to 56 micromoles g⁻¹, compared to 29 micromoles g⁻¹ for Heera and 84 micromoles g⁻¹ for N2-142. The best line (BCH-1773), with a glucosinolate profile made up of sinigrin (>95%) and a chromosome number of 2n = 34, was further evaluated in two environments (field and pots in open-air conditions). Average glucosinolate contents over the four environments included in this research were 42, 31 and 74 micromoles g⁻¹ for BCH-1773, Heera and N2-142, respectively. These are the lowest stable levels of glucosinolates reported so far in B. carinata.     

Synthesis of Acetylhomoagmatine

The first total synthesis of acetylhomoagmatine, a natural product isolated form the methanolic extracts from the sponge Cliona celata, is performed in four steps in a very high yield.     

Estimation of seed weight, oil content and fatty acid composition in intact single seeds of rapeseed ( Brassica napus} L.) by near-infrared reflectance spectroscopy

The potential of near-infrared reflectance spectroscopy (NIRS) for the simultaneous analysis of seed weight, total oil content and its fatty acid composition in intact single seeds of rapeseed was studied. A calibration set of 530 single seeds was analysed by both NIRS and gas-liquid chromatography (GLC) and calibration equations for the major fatty acids were developed. External validation with a set of 75 seeds demonstrated a close relationship between NIRS and GLC data for oleic (r = 0.92) and erucic acid (r = 0.94), but not for linoleic (r = 0.75) and linolenic acid (r = 0.73). Calibration equations for seed weight and oil content were developed from a calibration set of 125 seeds. A gravimetric determination was used as reference method for oil content. External validation revealed a coefficient of correlation between NIRS and reference methods of 0.92 for both traits. The performance of the calibration equations for oleic and erucic acid was further studied by analysing two segregating F2 seed populations not represented in the calibration set. The results demonstrated that a reliable selection for both fatty acids in segregating populations can be made by using NIRS. We concluded that a reliable estimation of seed weight, oil content, oleic acid and erucic acid content in intact, single seeds of rapeseed is possible by using NIRS technique. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sorption-desorption isotherms and biodegradation of glyphosate in two tropical soils aged with eucalyptus biochar

ABSTRACT

The objective of this study was to evaluate the sorption-desorption process and biodegradation of glyphosate in two tropical soils aged with biochar derived from eucalyptus. The biochar aging period was 30 d. There was little difference between the amounts of sorbed glyphosate in Ultisol (96.8, 96.8 and 96.4%) and Alfisol (97.1, 97.5 and 97.4%) soils that were unamended or amended with biochar aged for 0 or 30 d, respectively. Similar amounts of desorbed herbicide occurred in Ultisol (3.3, 3.3 and 3.4%) and Alfisol (4.1, 4.2 and 3.9%) soils, respectively. The degradation time half-life (DT50) of glyphosate in Ultisol unamended and initial amended were higher (38 and 36 d, respectively) than DT50 in the amended soil with 30 d of biochar aging (27 d); and in the Alfisol DT50 was higher in unamended soil (38 d), and similar in soil unamended at 0 and 30 d of biochar aging (21 and 26 d, respectively). The addition of biochar to two tropical soils or its aging did not have any effect on the sorption and desorption of glyphosate and its biodegradation in relation to the unamended soils, and it can did not affect the transport and persistence of this herbicide in soil.