Transitioning from standard to minimum tillage: Trade-offs between soil organic matter stabilization, nitrous oxide emissions, and N availability in irrigated cropping systems

Few studies address nutrient cycling during the transition period (e.g., 1–4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N₂O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize–tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced ¹⁵N-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 μm), microaggregates (53–250 μm) and silt-and-clay (<53 μm). We found a cropping system effect on soil N_new (i.e., N derived from ¹⁵N-fertilizer or -¹⁵N-cover crop), with 173 kg N_new ha⁻¹ in the conventional system compared to 71.6 and 69.2 kg N_new ha⁻¹ in the low-input and organic systems, respectively. In the conventional system, more N_new was found in the microaggregate and silt-and-clay fractions, whereas, the N_new of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-N_new than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-N_new was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N₂O emissions (39.5 g N₂O–N ha⁻¹ day⁻¹) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha⁻¹) produced intermediate N₂O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N₂O emissions, and N availability.     

Nomenclature and genetic relationships of apples and pears from Terceira Island

Heritage apple (Malus domestica Borkh. hybrids) and pear (Pyrus communis L. hybrid) trees grow in villages throughout Terceira Island, Azores, Portugal. Some of these pears have different names but similar morphology. The objective of this study was to determine synonymy, homology, and phylogeny of apples and pears from Terceira and to examine potential relationships of the island pears with standard apples and pears of Portuguese or American descent. Nine apple microsatellite markers were used to determine genetic relationships. Distance- and parsimony-based cluster analysis grouped these genotypes into separate apple and pear clades. The Terceira apples were divided into two clades: the maçā and the reineta-reinette. Among the 17 heritage apple genotypes, seven unique accessions were identified and four groups of synonyms, or possibly clones, were detected including: ‘Reineta Agosto’ and ‘Reineta Verde’ from Altares; ‘Reineta Castanha’ and ‘Reineta Verde Miuda’; ‘Maçā Pêra,’ ‘Maçā Calhau’, ‘Pêro Branco’ from Salga and from Terra-Chā and ‘Maçā Marmelo’; and the five genotypes ‘Maçā Sao Joao’, ‘Malápio Rosa’, ‘Maçā Gaspar’, ‘Maçā Branca’ and ‘Maçā Pato’. In addition, two homonyms were detected. ‘Pêro Vermelho’ from Terra Chā was a separate genotype from a tree from Doze Ribeiras of the same name, but Pêro Branco from Terra Chā appears to be a clone that can be distinguished by an additional allele at CH1F07a from a tree with that name from Salga. One pair of apple clones, ‘Reineta Agosto’ and ‘Reineta Verde’ from Altares appear to be derived from an unreduced gamete of ‘Golden Delicious.’ Another apple genotype ‘Maçā Acida’ could be a sibling of the ‘Maçā Pêra’ clonal group. Other tested standard apples from the US genebank were unrelated to Terceira genotypes. Of the seven heritage pears, five unique genotypes and one pair of synonyms were detected. ‘Pêra Papo Pintassilgo’ from Raminho and ‘Pêra Vermelha’ from the nursery of Serviço de Desenvolvimento Agario da Terceira (SDAT) were synonyms. ‘Passans du Portugal’ was related to ‘Pêra Cabaca’ but other standard pears from the US genebank were unrelated to Terceira genotypes. Future studies will include additional apple and pear cultivars from other Islands of the Azores and continental Portugal, and wild Asian species to further explore genetic relationships.     

The delay of flowering time in almond: a review of the combined effect of adaptation,mutation and breeding

Regulation of flowering time in almond, as in other Prunus species, is a complex process involving both chill and heat requirements. Following exposure to appropriate consecutive periods of cold and warm temperatures, the buds break dormancy and sprout or flower depending on bud type. To maximize flowering and subsequent vegetative growth and fruit set, chilling and ensuing warm temperature requirements have to be fully satisfied. Because of its potential for very early flowering, flowering time in almond is a major determinant of its adaptation to new environments. In colder regions, Late-flowering is often necessary to avoid frost damage during and just after flowering. Consequently, the selection of delayed flowering times remains an important objective in almond improvement programs. Flowering time is considered a quantitative though highly heritable trait. In addition, a dominant gene (Late flowering, Lb), originally identified in a spontaneous mutation of the Californian almond cultivar ‘Nonpareil’, was also described. The objective of this review is a comparative analysis of the effects of regional adaptation, breeding and mutation on the delay of flowering time in new almond cultivars. Findings indicate that the adaptation of almonds from the Mediterranean basin to colder regions in Northern Europe and America has been mainly achieved through delayed flowering. These adapted late-flowering cultivars have usually been developed by selecting desired quantitative genes within each regional germplasm. Additional progress thus appears achievable with a more comprehensive understanding of the quantitative and qualitative genetics controlling this trait. The use of molecular markers for the early selection of genes conferring late flowering, including both spontaneous mutations as well as unique regional germplasm, should allow development of even later cultivars including ultra-late cultivars flowering as into April.     

Reaction of <Emphasis Type="Italic">Phaseolus</Emphasis> spp. genotypes to ashy stem blight caused by <Emphasis Type="Italic">Macrophomina phaseolina</Emphasis>

Ashy stem blight (ASB) caused by Macrophomina phaseolina (Tassi) Goidanich (Mp) is a devastating seed-transmitted disease in common bean in the tropics. The identification of resistant cultivars throughout the cropping season contributes to disease management. Resistance is found in the primary and tertiary gene pools. Our objectives were to determine (1) the reaction of Phaseolus spp. genotypes to two Mp isolates at vegetative and reproductive stages, (2) the area under disease progress curve (AUDPC), and (3) resistant plants per genotype at harvest. Twenty-three genotypes from different origins were planted in the greenhouse in 2016 and 2017. One less-aggressive Mp (PRJD16) and one more-aggressive (PRI16) isolate were inoculated one and three times, respectively, by the cut-stem method. ‘Beníquez’, ‘Othello’, and ‘Verano’ were highly susceptible (mean scores >8.0, and AUDPC values from 264.6 to 300.8) to both isolates. BAT 477 and NY6020-4 were intermediate (5.6 and 6.2; AUDPC: 161.6 and 187.1) to PRJD16 and susceptible (7.4 and 8.2; AUDPC: 209.4 and 235.1) to PRI16. Resistant genotypes (mean scores ≤3) were not identified in this study. However, A 195, ‘Badillo’, and ‘PC 50’ possessed lower mean scores (4.3–5.4) and AUDPC values (126.4–150.9) to both isolates. Furthermore, A 195 had the highest percentage of resistant plants (55.6%) followed by PC 50, I9365-31, and PI 321637 (27.8%) to PRJD16 at harvest. Thus, the identification of resistant parents across Phaseolus species is necessary to increase the levels of ASB resistance in common bean cultivars throughout the entire cropping season.     

Bioefficacy of compounds from Dittrichia viscosa (Asteraceae) as protectant of chickpea seeds against the cowpea seed beetle Callosobruchus maculatus (Coleoptera: Chrysomelidae)

Journal of Plant Diseases and Protection - The efficacy of four bi- and tri-cyclic sesquiterpenes, namely inuloxins A, B and C and α-costic acid, extracted from aerial parts of Dittrichia...     

Developments in the nutrition of Menidia estor Jordan 1880

The Mexican silverside, Menidia estor, is a species with great regional importance and with very high prices in local markets. Unfortunately, due to high fisheries pressure, environmental degradation and pollution, the species has become endangered. Recently, there has been much progress in the biotechnology of this species, aimed at its culture, and the present paper describes the advances in feeding and nutrition of those important fish. M. estor is a stomachless, zooplantophagous fish, which also occasionally feeds on small fish and crustaceans in the adult stage. Studies on the digestive enzymatic activities show high proteolytic capacity and a late or different model of digestive maturation from that described for marine stomach fish. Nutritional studies on M. estor have shown that juveniles have dietary requirements of about 400 g kg^?1 protein and 80 mg kg^?1 vitamin C. The upper level of dietary carbohydrate for good growth and survival for juveniles is about 150 g kg^?1. Based on the high docosahexaenoic acid (DHA) content in flesh when fed on diets low in DHA, it is believed that the species has the capacity to biosynthetize >20‐carbon fatty acids from 18‐carbon fatty acids. The high levels of DHA in flesh makes this fish a very significant potential component of human nutrition. Using these findings the first practical diets for commercial culture of the species have been developed.     

Anaerobiosis in soybean root nodules under water stress

Soybean nodules subjected to water stress showed lowered C₂H₂ reducing activity and O₂ uptake, but enhanced CO₂ and ethanol evolution. Similar results were obtained with waterlogged nodules. The effects of stress could be partially or completely overcome by increaseing the O₂ supply. It is concluded that both water deficiency and excess may depress nitrogenase activity (C₂H₂ reduction) by restricting supplies of intermediates from aerobic pathways. At the same time fermentative pathways are stimulated and could lead to inhibitory concentrations of ethanol being produced. Both symbionts possess systems for ethanol production.     

Simultaneous determination of clofentezine,fenoxycarb and hexythiazox by HPLC on apples,pears and their pulps

The simultaneous HPLC determination of clofentezine, fenoxycarb and hexythiazox in apples, pears and their pulps is described. The method is based on a clean-up procedure carried out on a Seppak C18 cartridge followed by HPLC analysis on an RP-18 column using acetonitrile + water as mobile phase. Average recoveries were 85.0% for clofentezine, 84.8% for fenoxycarb and 75.6% for hexythiazox on apple matrix; recoveries from pear matrix were in the same range. UV detection limits at 240 nm were 0.07 mg kg^?1 for clofentezine, 0.064 mg kg^?1 for fenoxycarb and 0.08 mg kg^?1 for hexythiazox.     

Effect of ammonium sulfate fertilization on bahiagrass quality and copper metabolism in grazing beef cattle

To assess the impact of S fertilization on bahiagrass (Paspalum notatum) quality and Cu metabolism in cattle, two studies were conducted during the summer grazing season (1999 and 2000). Pasture replicates (16.2 ha; n = 2/treatment) received the same fertilizer treatment in each growing season, consisting of 1) 67 kg N/ha from ammonium sulfate (AS), 2) 67 kg N/ha from ammonium nitrate (AN), and 3) control (no fertilizer; C). Forage sampling was conducted at 28-d intervals following fertilization by the collection of whole plants (four samples/pasture) in randomly distributed 1-m2 grazing exclusion cages and analyzed for CP, in vitro organic matter digestibility, S, P, Ca, K, Mg, Na, Fe, Al, Mn, Cu, and Zn. To determine the effect of fertilizer treatment on liver trace mineral concentrations in grazing cattle, random liver tissue samples were collected (n = 12; four/treatment) at the start and end of the study period in 2000. Ammonium sulfate fertilization increased (P < 0.001) forage S concentration in both years. Plant tissue N concentrations were increased by N fertilization, regardless of source, in 2000, but not in 1999. Cows grazing AS pastures had lower (P < 0.05) liver Cu concentrations at the end of the study period in 2000 compared to AN and C. In Exp. 2, 37 Cu-deficient heifers grazing AS fertilized pastures were obtained from the same location and allocated to one of two treatments, consisting of supplements providing 123 mg/d of either inorganic (Cu sulfate; n = 12) or organic (Availa-Cu; n = 15) Cu. Treatments were delivered for 83 d. Liver Cu increased over time in all heifers regardless of treatment; however, heifers supplemented with Availa-Cu tended (P = 0.09) to have higher mean liver Cu concentrations than those receiving Cu sulfate. The results of these studies indicate that AS fertilization of bahiagrass increases forage S concentrations. When provided free-choice access to a complete salt-based trace mineral supplement, cows grazing AS-fertilized pastures had lower liver Cu concentrations than cows grazing pastures fertilized with AN; upon removal from high-S pastures, cattle were able to respond to Cu supplementation.     

A Combination Chemotherapy Protocol (VELCAP-L) for Dogs with Lymphoma

Ninety-eight dogs with lymphoma treated with a 5-drug combination chemotherapy regimen (vincristine, L-asparaginase. cyclophosphamide, doxorubicin, prednisone [VELCAP-L]) were evaluated for pretreatment characteristics predictive for response and remission duration. The complete remission rate was 69%, with a median remission duration of 55 weeks. Dogs with advanced stage of disease, constitutional signs, dogs that were older, and dogs that were dyspneic were less likely to achieve remission. Once in remission, small dogs and dogs without pretreatment thrombocytopenia were likely to have longer remission duration. Toxicoses were frequent, but rarely fatal, and no predictitive factors were found for a dog developing toxicoses. VELCAP-L is an effective treatment for dogs in stage I-III lymphoma, particularly in young, small animals.