Responses of tomato hybrid cultivars to soil application of humic acid under greenhouse conditions

Responses of three tomato (Lycopersicon esculentum Mill.) hybrids viz. 'Luanova', 'Savarona' and 'Tessera' to various doses (0, 0.5, 1.0, 1.5 and 2.0 g L-1) of soil application of humic acid (HA) were evaluated in terms of plant growth, productivity and quality of fruits, under greenhouse conditions, during 2011-12 and 2012-13. In addition to improved quality characteristics, higher values for yield and yield components were recorded for tomato fruits harvested from plants of 'Tessera' cultivar compared to those harvested from other hybrids tested, regardless of growing seasons. Plants from 'Luanova' cultivar were, however, earlier in fruiting with higher number of fruits per plant. Soil application of HA presented positive effects on yield and physicochemical quality of tomato fruits irrespective of the dose of HA and the cultivar investigated, in both seasons. Soil application of HA at higher dose 1.5 g L-1 exhibited better results in all the three tomato cultivars tested, in terms of their vegetative and reproductive growth, and significantly improved the physicochemical quality of their fruits. Conclusively, the tomato hybrid 'Tessera' was found suitable for cultivation under greenhouse conditions while soil application of aqueous solution of HA @ 1.5 g L-1 substantially resulted in higher production of quality tomato fruits.

Soil fertility management for groundnut in the lowveld of Mpumalanga and north coastal plain of KwaZulu-Natal provinces of South Africa

Smallholder groundnut production contributes substantially to food security in Mpumalanga Lowveld (MLV) and in Manguzi, the northern coastal plain (NCP) of KwaZulu Natal (KZN), both of which are dominated by infertile structureless sandy soils. A study was conducted to obtain information on the chemical properties of the soils to guide fertilizer management for optimizing groundnut production on these soils. Soil samples were collected from representative sites in MLV and NCP, and analysed for pH, calcium (Ca), magnesium (Mg), potassium (K), phosphorous (P), zinc (Zn) and manganese (Mn) in the peg-zone (0-10 cm depth), root zone (10-40 cm depth) and subsoil (40-60 cm depth). The soils were largely acidic, with pH mostly falling below 5.5. The basic cation concentrations were generally low, and so were Zn and Mn concentrations. Nonetheless, with the exception of P and Mn, the soil concentrations of the other nutrients analysed were within ranges considered adequate for vegetative and reproductive growth of groundnut, though Zn was marginally so. General fertility management recommendations to inform agricultural extension are provided for groundnut production on the sandy soils based on the chemical analyses of the soils.

Standardization of stage wise water requirement in drip irrigated Kinnow mandarin orchards under sub-tropical conditions

An experiment on drip irrigation scheduling based on pan evaporation replenishment was conducted in Kinnow orchard at Punjab Agricultural University, Ludhiana during 2010-2018. Year was divided into six stages (stage 1 to stage VI) including two months in each stage. First treatment included irrigation scheduling with 30 and 40% ER, treatment two with 40 and 60% ER, treatment three with 60 and 80% ER, alternatively during stages I to VI. However, fourth and fifth treatments had irrigation with 80% ER and 30% ER, respectively, in all the stages. Maximum daily open pan evaporation (9.15 mm) was recorded in May and minimum (1.19 mm) was recorded in January. The water requirement varied from 2.8 liters day-1 tree-1 in stage-I to 58.3 liters day-1 tree-1 in stage-III. Linear increase in vegetative and reproductive growth was observed with increase in irrigation water. Polynomial relationship studies indicated the increase in water quantity applied to Kinnow with increase in temperature subject to the prevailing relative humidity. Similarly, volumes of water applied increased with increased mean evaporation. The study concluded that drip irrigation scheduling with 60 to 80% ER alternatively, starting from January to December save significant amount of water, without affecting yield and quality of Kinnow under subtropical conditions.

Evapotranspiration and Quantitative Partitioning of Spring Maize with Drip Irrigation under Mulch in an Arid Region of Northwestern China

To examine evapotranspiration (ETc), soil evaporation (Es), and transpiration (Tr), and partitioning of ETc, a two-year field experiment was carried out in a maize field with drip irrigation under mulch in an arid region of northwestern China in 2017 and 2018. In the experiment we designed two treatments with full irrigation (T1) and growth stage-based strategic regulated deficit irrigation (T2). The applied irrigation of T2 was 40% of the T1 during both late vegetative and reproductive growth stages. Based on the measurements of soil water content (SWC) and Tr, a dual crop coefficient model (SIMDualKc) was calibrated and validated, and daily ETc, Es, and Tr were estimated. The model can simulate well the dynamic variations of SWC and Tr. The calibrated basic crop coefficient at the initial, mid-season, and end growth stages was 0.2, 1.15, and 0.75, respectively. The ETc was 507.9 and 519.1 mm for the T1 treatment, and 428.9 and 430.9 mm for the T2 treatment. The ratios of Tr to ETc were higher for the two treatments, ~90%, for two years. Collectively, both drip irrigation under mulch and strategic deficit irrigation after canopy covering of the ground can significantly reduce the ineffective proportion of ETc and Es.

Evaluating the Spectral Response and Yield of Soybean Following Exposure to Sublethal Rates of 2,4-D and Dicamba at Vegetative and Reproductive Growth Stages

The commercialization of synthetic auxin-resistant crops and the commensurate increase in post-emergent auxin-mimic herbicide applications has resulted in millions of hectares of injury to sensitive soybeans in the United States since 2016. Visual yield loss estimations following auxin injury can be difficult. The goal of this research was to determine if spectral variations following auxin injury to soybean allow for more precise yield loss estimations. Identical field experiments were performed in 2018, 2019, and 2020 in Columbia, Missouri to compare the ability of established vegetative indices to differentiate between exposure levels of 2,4-D and dicamba in soybean and predict yield loss. Soybeans were planted at three timings for growth stage separation and were exposed to sublethal rates of 2,4-D and dicamba at the R2, R1, and V3 growth stages. A UAV-mounted multispectral sensor was flown over the trial 14 days after the herbicide treatments. The results of this research found that vegetative indices incorporating the red-edge wavelength were more consistent in estimating yield loss than indices comprised of only visible or NIR wavelengths. Yield loss estimations became difficult when soybean injury occurred during later reproductive stages when soybean biomass was increased. This research also determined that when injury occurs to soybean in vegetative growth stages late in the growing season there is a greater likelihood for yield loss to occur due to decreased time for recovery. The results of this research could provide direction for more objective and accurate evaluations of yield loss following synthetic auxin injury than what is currently available.

Morpho-Physiological Classification of Italian Tomato Cultivars (Solanum lycopersicum L.) According to Drought Tolerance during Vegetative and Reproductive Growth

Irrigation is fundamental for agriculture but, as climate change becomes more persistent, there is a need to conserve water and use it more efficiently. It is therefore crucial to identify cultivars that can tolerate drought. For economically relevant crops, such as tomatoes, this purpose takes on an even more incisive role and local agrobiodiversity is a large genetic reservoir of promising cultivars. In this study, nine local Italian cultivars of tomatoes plus four widely used commercial cultivars were considered. These experienced about 20 d of drought, either at vegetative or reproductive phase. Various physio-morphological parameters were monitored, such as stomatal conductance (gs), photosynthesis (A), water use efficiency (WUE), growth (GI) and soil water content (SWC). The different responses and behaviors allowed to divide the cultivars into three groups: tolerant, susceptible, and intermediate. The classification was also confirmed by a principal component analysis (PCA). The study, in addition to deepening the knowledge of local Italian tomato cultivars, reveals how some cultivars perform better under stress condition than commercial ones. Moreover, the different behavior depends on the genotype and on the growth phase of plants. In fact, the Perina cultivar is the most tolerant during vegetative growth while the Quarantino cultivar is mostly tolerant at reproductive stage. The results suggest that selection of cultivars could lead to a more sustainable agriculture and less wasteful irrigation plans.

Is the Life History Flexibility of Cold Desert Annuals Broad Enough to Cope with Predicted Climate Change? The Case of Erodium oxyrhinchum in Central Asia

Interannual seasonal variability in precipitation may strongly affect the life history and growth of desert annual plants. We compared the effects of dry and wet springs and dry and wet autumns on growth and F2 seed dormancy of plants from spring (SG)- and autumn (AG)-germinated seeds of the cold desert annual Erodium oxyrhinchum. Vegetative and reproductive growth and F2 seed dormancy and germination were monitored from September 2016 to November 2020 in the sandy Gurbantunggut Desert in NW China in Central Asia. Dry autumns decreased the density of AG plants, and dry springs decreased the density of SG plants and growth of SG and AG plants. In dry springs, SG plants were more sensitive to precipitation than AG plants, while in wet springs SG and AG plants had similar responses to precipitation. During growth in both dry and wet springs, most morphological characters of SG and AG plants initially increased rapidly in size/number and then plateaued or decreased, except for SG plants in dry springs. In dry springs, most morphological characters of AG plants were larger or more numerous than those of SG plants, and they were larger/more numerous for SG plants in wet than in dry springs. The percentage biomass allocated to reproduction in SG plants was slightly higher in a wet than in a dry spring. A much higher proportion of dormant seeds was produced by AG plants in a wet spring than in a dry spring. Projected changes in precipitation due to climate change in NW China are not likely to have much of an effect on the biology of this common desert annual plant.