Computation of vapour pressure deficit and crop transpiration via development of a web based computer module

The plant water or nutrient requirement under greenhouse conditions is mainly governed by crop transpiration in a linear relation to vapour pressure deficit (VPD), particularly in soilless production systems. Being a cooling process in plants, transpiration governs the plant water requirement in relation to the subjected microclimatic conditions and VPD can be used as a tool to maintain greenhouse crop transpiration to optimal range for obtaining desired crop yields. Thus, the present investigation was undertaken to study the integrated effect of temperature (Tapc), relative humidity (Eapc) and solar radiation (Irad) on VPD and crop transpiration. A computer module was developed to monitor the behavior of the VPD and thereby the crop transpiration through charts under greenhouse conditions. The VPD indicated a linear increasing trend with Tapc (R2≥0.84) and decreasing trend with Eapc (R2=0.99), demonstrating a strong correlation in both cases. The increasing crop transpiration with VPD, particularly under hot climatic conditions significantly increased the input water and nutrient requirements of the crop. Thus, transpiration in relation to VPD should be considered as a factor for fertigation scheduling and improving irrigation control in soilless systems. Moreover, maintaining Tapc, Eapc and VPD within range of 22-27°C, 60-80% and 0.53-1.10 kPa may help to control the crop transpiration, manage the greenhouse irrigation and fertigation, and thus improve the cucumber yield.

Management of Meloidogyne incognita on cucumber with a new nonfumigant nematicide fluopimomide

Cucumber is an economically important vegetable crop in China. Southern root-knot nematode (Meloidogyne incognita) is a significant obstacle in cucumber production, causing severe root damage and yield losses. Moreover, resistance development to fosthiazate, and poor mobility of abamectin have led to failure to control this nematode. It is of great interest to growers and the vegetable industry to explore novel nonfumigant nematicides that can provide adequate control in an environmentally friendly manner. Fluopimomide, a new chemical having a similar structure to fluopyram, was shown to exhibit toxic effects on fungi and nematodes. The efficacy of fluopimomide to reduce infection of M. incognita in cucumber was evaluated under greenhouse and field conditions. In the greenhouse, fluopimomide at all test rates resulted in a 22.5-39.6% and 31.3%-55.0% reduction in the population density of M. incognita in the soil at 30 and 60 days after treatment (DAT), respectively, compared with the non-treated control. Fluopimomide at 500 and 750 g ha-1 reduced (p < 0.05) root galling, meanwhile increasing plant height compared to the non-treated control at 30 and 60 DAT. In the field trials, fluopimomide at 500 and 750 g ha-1 decreased the population density of M. incognita and root galling 57.2-69.9% compared to the untreated control, while enhancing cucumber yield in two consecutive years. Furthermore, fluopimomide at 500 g ha-1 combined with fosthiazate was the most effective treatment showing a synergistic effect on reducing population densities of M. incognita, which was significantly greater than either fluopimomide or fosthiazate by themselves. In summary, fluopimomide has considerable potential for managing M. incognita on cucumber.

Case Study on the Use of the Leaf-Count Method for Drip Fertigation in Outdoor Cucumber Cultivation in Reconstructed Fields Devastated by a Tsunami

Drip fertigation was tested in fields using a nitrogen fertilization method based on leaf increments, with the aim of increasing the cucumber yield in outdoor fields restored after the tsunami disaster in Rikuzentakata City, Iwate Prefecture, in 2011. The 2016 test site (Takata field) was restored as a paddy field, and there were problems with water retention and gravel contamination. The condition of the 2017 test site (Yonesaki field) was better than that of the 2016 site. The drip fertigation method increased cucumber yield by 93% and 27% in the Takata and Yonesaki fields, respectively, when compared to the yield from fields cultivated conventionally. Drip fertigation enables the constant supply of liquid fertilizer to the rhizosphere, and the easy application prevents the scarcity of fertilizer, especially at later stages of growth. In contrast, a real-time soil diagnosis, using the Dutch 1:2 soil–water extract method, was unsuccessful due to flooding, especially in the Takata field. As the purpose of this method is not to reduce the amount of nitrogen provided, but to increase the yield, and because it is difficult to precisely control the application of fertilizer due to precipitation, we suggest that the real-time soil diagnosis and feedback should be omitted to further simplify fertilizer application.

The Effect of Hand Pollination on the Yield of African Horned Cucumber (Cucumis metuliferus E. May. Ex Naudin) Grown under Protected Environments

Pollination is the process by which pollen grains are exchanged in plant flowers to allow for fertilisation and production to take place. However, challenges occur when crops are grown under protected structures where there are minimal activities of natural pollination agents such as wind and animals which are responsible for transferring pollen grains from the anther to the stigma. Therefore, the study objective was to determine the effect on hand pollination on the yield of African horned cucumber grown under greenhouse and shade net environment. A factorial experiment with two factors (hand pollinated and non-hand pollinated/control) was conducted under two different growing environments (greenhouse and shade net). African horned cucumber plants were hand self-pollinated in the morning. Pollen were manually transferred with a hand using the new earbud from the male to the female flowers on the same plant (selfing). Results showed that hand pollinated African horned cucumber plants increased total biomass from 0.93 to 2.23 kg under greenhouse environment. Hand pollinated plants increased harvest index from 0.07 to 0.35 under shade net environment. It can thus, be deduced that hand pollination increases African horned cucumber yield in the greenhouse and shade net environments.

Performance of Greenhouse-Grown Beit Alpha Cucumber in Pine Bark and Perlite Substrates Fertigated with Biofloc Aquaculture Effluent

Using aquaculture effluent (AE) to fertigate plants is gaining popularity worldwide. However, in substrate-based systems, the choice of substrate is essential due to their effects on crop productivity. Differences in the retention of nutrients by substrates makes it necessary to assess suitability for use in AE. This study was conducted from January to July in 2016 and September to October in 2019 to evaluate greenhouse-grown Beit Alpha cucumber (Cucumis sativus L. ’Socrates’) performance fertigated with AE in pine bark or perlite substrates, grown either as one plant or two plants per pot. A 2 × 2 factorial arrangement in a randomized complete block design with four replications for each season was used. The substrate effect on yield in 2016 depended on the density and season. The pooled yield over seasons in 2016 showed pine bark had a significantly higher yield than perlite by 11% in one plant per pot but lowered by the same amount in two plants per pot. In 2019, pine bark significantly reduced the leachate pH in both plant densities and reduced the leachate EC by about 15% in two plants per pot. The foliar boron was occasionally below sufficiency whilst manganese was above sufficiency in pine bark due to its inherently low pH. We conclude that the effect of the substrates on cucumber yield fertigated with AE is dependent on the season and the number of plants per pot. Therefore, due to the local availability of pine bark, it could be a potential substitute for perlite especially when using one plant per pot for AE. In addition, pine bark could be used as an intermediate substrate to reduce the pH in AE for downstream use.

Effect of Drip Irrigation Frequency, N-Fertilization, and Mulching on Yield, Nitrogen, and Water Use Efficiencies of Cucumber (Cucumis sativus L.) in Ikole-Ekiti, Nigeria

Soil moisture conservation, proper irrigation scheduling and nutrient management are crucial for sustainable cucumber production. A field experiment was set up over two years (2018 and 2019) to investigate the effects of irrigation frequency, black polyethylene mulching, and nitrogen fertilization on cucumber yield, water use efficiency (WUE) and nutrient use efficiency (NUE) at Ikole-Ekiti, Nigeria. The experiment was a 3 x 2 x 2 factorial in a randomized complete block design (RCBD) with a split-plot arrangement and the main plot as drip irrigation frequency: twice per week (I4), three times per week (I5), and four times per week (I6), while the sub-plots were nitrogen fertilization; (no fertilizer, N0 and 180 kg/ha urea, N180) and mulching (no mulch, NM and mulch, M). The highest yield (8.39 and 8.51 t/ha) with the best WUE was obtained from treatment I4MF (F, fertilization), while the lowest (5.81 and 5.79 t/ha) was obtained from I6MF for the respective years. The combination of variables significantly (P<0.05) influenced cucumber yield, WUE, and NUE, and significant correlations were obtained (r=0.87** and 0.85**) between WUE and fruit yield for the study years. The treatment I4MF therefore, could successfully be adopted to reduce water and fertilizer application for improved cucumber yield in the field.

«Lighting price» of cucumber yield in the winter-spring turnover of greenhouses

Relevance. Among the main factors that determine the productivity of vegetable yields in protected ground, the main one is light. For the formation of 1 kg/m2 of cucumber fruits with a length of 18-22 cm, on average about 3500-4000 J/cm2 of solar radiation is required. In the winter-spring cycle, in the absence of artificial lighting in greenhouses, there is an unevenness of scattered solar radiation and a general shortage of incoming light energy. At the same time, the amount of total solar radiation required for the formation of a 1 kg of fruit ("lighting price") is not the same for different hybrids. To increase the profitability of production in the winter-spring turnover in greenhouses that are not equipped with artificial lighting, it is necessary to choose hybrids with the lowest "lighting price" of the crop, that is, hybrids that use less light energy to form a 1 kg of fruit.The purpose of the study: evaluation of F1 hybrids of cucumber on the basis of resistance to lack of lighting by comparing their "lighting price" of the crop: how much energy is spent on the formation of 1 kg of marketable products.Methods. The research was carried out at the variety testing site in the Crimean breeding Center of the Scientific Research Institute of Vegetable Crop Selection "Gavrish", in the conditions of winter-spring turnover, in greenhouses not equipped with artificial lighting. We tested seven medium-fruited (18-22 cm) spined-fruited cucumber hybrids recommended for growing in winter-spring turnover.Results. The analysis of the data on the input of solar radiation and the formation of a standard yield showed that there is a direct relationship between the amount of incoming light and the level of productivity. The period of conversion of the received solar energy into the fruit harvest varied during the growing season from 14 to 8 days, depending on the degree of plant development. The "lighting price" of the crop was not the same for different hybrids: the hybrids tested in the experiment spent an average of 2900 J/cm2 per 1 kg of product, which is 18% more efficient than for standard greenhouse cucumbers.

Impact of Seaweed Liquid Extract Biostimulant on Growth, Yield, and Chemical Composition of Cucumber (Cucumis sativus)

Seaweed extract biostimulants are among the best modern sustainable biological plant growth promoters. They have been proven to eliminate plant diseases and abiotic stresses, leading to maximizing yields. Additionally, they have been listed as environmentally friendly biofertilizers. The focus of the present research is the use of a commercial seaweed biostimulant as an eco-friendly product (formally named True Algae Max (TAM). During the 2017 and 2018 seasons, five treatments of various NPK:TAM ratios were applied via regular fertigation, namely a conventional treatment of 100% NPK (C0) alongside combinations of 25%, 50%, 75%, and 100% (C25, C50, C75, and C100) of TAM, to evaluate the effectiveness of its bioactive compounds on enhancing growth, yield, and NPK content of cucumber (Cucumis sativus) under greenhouse conditions. TAM is rich in phytochemical compounds, such as milbemycin oxime, rhodopin, nonadecane, and 5-silaspiro [4.4]nona-1,3,6,8-tetraene,3,8-bis(diethylboryl)-2,7-diethyl-1,4,6,9-tetraphenyl-. Promising measured parameter outcomes showed the potentiality of applying TAM with and without mixes of ordinary NPK application. TAM could increase cucumber yield due to improving chemical and physical features related to immunity, productivity, and stress defense. In conclusion, it is better to avoid applying mineral fertilizers, considering also that the organic agricultural and welfare sectors could shortly depend on such biotechnological tools and use them to fulfill global food demands for improved sustainability.