Growth, nutrient uptake and tipburn severity of hydroponic lettuce in response to electrical conductivity and K:Ca ratio in solution

1994 ◽  
Vol 45 (1) ◽  
pp. 251 ◽  
Author(s):  
DO Huett
Keyword(s):  
Electrical Conductivity ◽  
Nutrient Uptake ◽  
Nutrient Solution ◽  
Growth Period ◽  
Vegetable Crops ◽  
Standard Formulation ◽  
Fresh Weight ◽  
Concentration Maximum ◽  
Young Leaves ◽  
Number Of Leaves

A commercial hydroponic nutrient solution formulation was developed to reflect the high K:N uptake of a range of vegetable crops (Huett and Dettmann, Aust. J. Agric. Res. 1992, 43, 1653-65). This standard formulation had a K:N ratio of 1.7: 1.0 and a K:Ca ratio of 1.25 : 1 00 (equivalent weight basis). Head lettuce cv. Coolguard and cv. Fame and non-heading cv. Red Mignonette were grown in recirculating culture to maturity with the standard formulation to examine the effect of electrical conductivity (EC) (0.4-3.6 dS m-l) and, for the latter two cultivars, nutrient formulation K: Ca ratio (from 1.00:3.50 to 3.50: 1-00) on growth, nutrient uptake and tipburn severity. Plants grown at an EC of 0.4 dS m-l were N and K deficient, while recently matured leaves and youngest leaves contained the highest Ca concentrations which decreased with increasing EC. When cv. Coolguard was grown at an EC of 1.0 dS m-l, N and K deficiency was eliminated and leaves contained the highest Ca concentration. Maximum fresh weight of leaf and head was recorded at 1-6 dS m-' and the decline in nutrient solution N and K concentrations over the growth period was 13 and 42% respectively. An increase in the K: Ca ratio of the formulation increased (P < 0-05) leaf by 13% and leaf+head fresh weight at maturity by 10% for cv. Fame whereas, for cv. Red Mignonette, a reduction in the K : Ca ratio increased ( P < 0.05) leaf fresh weight by 29% compared with the standard formulation. A reduction in the K : Ca ratio increased ( P < 0.05) the Ca concentration in the youngest leaves of cv. Fame and of cv. Red Mignonette at 1.6 and 3.6 dS m-l. Leaf K concentrations were generally reduced ( P < 0.05) by low EC and low K:Ca ratio. Hot conditions led to tipburn developing in cv. Red Mignonette at the 2 week harvest. The number of leaves plant-1 with tipburn at maturity (week 3) was reduced ( P < 0.01) from 23.1 to 4.4 as EC was reduced from 3.6 to 0 - 4 dS m-1 and was reduced ( P < 0 05) from 15.2 to 12.3 as the nutrient formulation K : Ca ratio was reduced from 3.5 : 1.0 to 1.25 : 1.00. Over the last week of the growth period, the number of leaves with tipburn remained stable at an EC of 0-4 dS m-l whereas, at 3.6 dS m-l, the number of leaves with tipburn increased by 253%. Tipburn developed in young leaves of cv. Red Mignonette which had a Ca concentration range from 1.7 to 3.2 g kg-1 and was generally absent from recently matured leaves which had a Ca concentration of 11.0 g kg-1. Young leaves of the tolerant cv. Fame had a Ca concentration of 5-9 g kg-1.

Broccoli (Brassica oleracea var. italica) cultivar response to boron deficiency

1992 ◽  
Vol 72 (3) ◽  
pp. 883-888 ◽  
Author(s):  
B. J. Shelp ◽  
R. Penner ◽  
Z. Zhu
Keyword(s):  
Brassica Oleracea ◽  
Nutrient Solution ◽  
Nutrient Deficiency ◽  
Boron Deficiency ◽  
Fresh Weight ◽  
High Susceptibility ◽  
Inflorescence Development ◽  
Shoot Fresh Weight ◽  
Young Leaves ◽  
Percent Decline

Broccoli (Brassica oleracea var. italica) cultivar, Commander, characterized by low susceptibility to the hollow stem disorder commonly associated with boron (B) deficiency was compared to one with high susceptibility (cv. Stolto) and to two which are grown commercially (cvs. Baccus and Premium Crop). Beginning 3 wk after germination plants grown in a glasshouse in vermiculite were supplied continuously with a nutrient solution containing adequate B (0.5 mg L−1) or none (deficient), or were supplied initially with 0.5 mg B L−1 up to the initiation of inflorescence development after which no B was supplied. All cultivars showed visible symptoms of B deficiency (leaf midrib cracking, stem corkiness, necrotic lesions and hollowing in the stem pith) and reductions in shoot fresh weight with the zero B treatment, but Commander was least affected. Also, the B concentrations of the florets from Commander were highest and showed the lowest percent decline relative to the 0.5 mg B L−1 treatment. When B was removed from the nutrient solution at initiation of inflorescence development, the B concentrations of the florets and young leaves of all cultivars were higher than in the zero B treatment. Compared to the 0.5 mg B L−1 treatment, the B concentrations of old leaves from all cultivars were reduced, but only in Premium Crop was the floret B significantly decreased.Key words: Boron nutrition, Brassica, broccoli, nutrient deficiency, retranslocation

scholarly journals PEG-8000 Alters Morphology and Nutrient Concentration of Hydroponic Impatiens

HortScience ◽  
2005 ◽  
Vol 40 (6) ◽  
pp. 1768-1772 ◽  
Author(s):  
Stephanie Burnett ◽  
Marc van Iersel ◽  
Paul Thomas
Keyword(s):  
Electrical Conductivity ◽  
Polyethylene Glycol ◽  
Nutrient Uptake ◽  
Plant Height ◽  
Nutrient Solution ◽  
Nutrient Concentration ◽  
Nutrient Deficiency ◽  
Foliar Tissue ◽  
Impatiens Walleriana ◽  
Peg 8000

Osmotic compounds, such as polyethylene glycol 8000 (PEG-8000), reduce plant elongation by imposing controlled drought. However, the effects of PEG-8000 on nutrient uptake are unknown. Impatiens `Dazzler Pink' (Impatiens walleriana Hook. F.) were grown hydroponically in modified Hoagland solutions containing 0, 10, 17.5, 25, 32.5, 40, 47.5, 55, or 62.5 g·L–1 PEG-8000. Impatiens were up to 68% shorter than control plants when grown with PEG-8000 in the nutrient solution. Plants treated with PEG-8000 rates above 25 g·L–1 were either damaged or similar in size to seedlings treated with 25 g·L–1 of PEG-8000. Impatiens leaf water potentials (Ψw) were positively correlated with plant height. PEG-8000 reduced the electrical conductivity of Hoagland solutions as much as 40% compared to nontreated Hoagland solutions, suggesting that PEG-8000 may bind some of the nutrient ions in solution. Foliar tissue of PEG-treated impatiens contained significantly less nitrogen, calcium, zinc, and copper, but significantly more phosphorus and nickel than tissue from nontreated impatiens. However, no nutrient deficiency symptoms were induced.

scholarly journals Effect of N:K Ratio and Electrical Conductivity of Nutrient Solution on Growth and Yield of Hydroponically Grown Golden Thistle (Scolymus hispanicus L.)

Proceedings ◽  
2020 ◽  
Vol 30 (1) ◽  
pp. 87
Author(s):  
Dimitrios Papadimitriou ◽  
Emmanouil Kontaxakis ◽  
Ioannis Daliakopoulos ◽  
Thrassyvoulos Manios ◽  
Dimitrios Savvas
Keyword(s):  
Electrical Conductivity ◽  
Nutrient Solution ◽  
Chlorophyll Concentration ◽  
Tuberous Root ◽  
Growth And Yield ◽  
Nutrient Concentrations ◽  
Fresh Weight ◽  
Natural Habitats ◽  
High Quality ◽  
Hydroponic Cultivation

As the demand for high-quality wild greens rises, due to their high nutritional, culinary, and medicinal properties, the potential overexploitation and excessive disruption of their natural habitats bring serious environmental problems to the foreground. However, new alternative cultivation techniques, such as hydroponic cultivation, could take advantage of rational water management, optimal fertilization management and climate adaptation, to produce high-quality wild greens, all year round. As an initial step to assess optimal hydroponic cultivation conditions for golden thistle (Scolymus hispanicus L.), in this study we evaluated the effect of N:K ratio and electrical conductivity (EC) in the supplied nutrient solution on plant growth, yield and phenology. Four nutrient solutions were applied with a low or a high N:K ratio (1.59 or 2.38 mol/mol, respectively) combined with a low or a high electrical conductivity (EC) level (2.2 and 2.8 dS m−1, respectively) in a 2 × 2 factorial experiment set as a completely randomized block design with 4 blocks and 48 plants per block. Golden thistle seedlings were planted in plastic growth-bags of hydroponic perlite substrate in an open, drip-irrigated, soilless cultivation system. The experiment commenced in December 2018, in a plastic greenhouse at the campus of the Hellenic Mediterranean University, Crete, Greece. After four months of cultivation, the post-harvest analysis showed that the high N:K ratio significantly increased the fresh weight of leaf and edible tuberous root, whereas the tested EC levels in the nutrient solution had no impact on plant fresh weight. The experimental treatments did not significantly affect leaf chlorophyll concentration (SPAD meter readings), chlorophyll fluorescence (Fv/Fm) or the number of leaves and the specific weight of the tuberous root of the plants. Our results indicate that wild golden thistle could be domesticated as an edible vegetable, and cultivated hydroponically at different seasons of the year using relatively low nutrient concentrations, thereby minimizing aquifer nitrate and phosphate pollution. A nutrient solution with a relatively high N:K ratio (here 2.38 mol/mol) is recommended for the hydroponic cultivation of golden thistle.

scholarly journals Growth and yield of lettuce plants under salinity

2005 ◽  
Vol 23 (4) ◽  
pp. 931-934 ◽  
Author(s):  
Jerônimo L. Andriolo ◽  
Gean L. da Luz ◽  
Maiquel H. Witter ◽  
Rodrigo dos S. Godoi ◽  
Gisele T. Barros ◽  
...  
Keyword(s):  
Experimental Design ◽  
Nutrient Solution ◽  
Dry Mass ◽  
Growth And Yield ◽  
Fresh Weight ◽  
Electrical Conductivities ◽  
Salinity Levels ◽  
Number Of Leaves ◽  
Set Up ◽  
Positive Effect

Lettuce plants, cv. Vera, were grown under five salinity levels in a hydroponical experimental set-up using a 0.15 m deep sand growing bed. A standard nutrient solution was used, with the following composition, in mmol L-1: 16.9 NO3-; 2.0 H2PO4-; 1.0 SO4- 4.0 Ca++; 10.9 K+ e 1.0 Mg++, and, in mg L-1, 0.42 Mn; 0.26 Zn; 0,05 Cu; 0,50 B; 0,04 Mo, and 4.82 chelated Fe. The five salinity levels compared as treatments were obtained by varying the concentration of the standard nutrient solution, reaching average electrical conductivities (EC) of 0.80; 1.93; 2.81; 3.73 and 4.72 dS m-1, for T1, T2, T3, T4 and T5, respectively. The nutrient solution at each salinity level was supplied from a reservoir by means of a flooded-type electrical pump, for 15 minutes, at intervals of 90 minutes during the day and 420 minutes during the night. A completely randomised experimental design was used with four replications and 20 plants per plot. Four plants of each plot were harvested at 32 days after planting, to determine shoot and root dry mass, shoot fresh weight, leaf area and number of leaves per plant. Number of leaves was 18 per plant and was not affected by treatments. Dry mass of leaves increased 24,4% from T1 to T3. No relationships were found on data from stem and root dry mass. A positive effect of EC was recorded on shoot fresh mass, which increased 28.5% from T1 to T2, and decreased 16.5% from T2 to T5. Maximum LAI estimated value was 4.3 m² m-2 for an EC of 2.6 dS m-1. Salinity levels above 2.0 and 2.6 dS m-1 reduce fresh yield and plant growth, respectively.

scholarly journals Pengaruh Aplikasi Pupuk Mikotricho pada Budidaya Bawang Merah dengan Pengurangan Dosis Pupuk N-P-K (The Effect of Mikotricho Fertilizer Application on Shallots Cultivation by Reducing the N-P-K Dose)

2020 ◽  
Vol 30 (1) ◽  
pp. 47
Author(s):  
Eny Rokhminarsi ◽  
Darini Sri Utami ◽  
NFN Begananda
Keyword(s):  
Leaf Area ◽  
Manufacturing Industry ◽  
Fertilizer Application ◽  
Growth And Yield ◽  
Vegetable Crops ◽  
Fresh Weight ◽  
Plant Weight ◽  
Reduced Dose ◽  
Number Of Leaves ◽  
Synthetic Fertilizers

<p>Bawang merah termasuk sayuran bumbu yang dibutuhkan oleh masyarakat dan harganya bersifat fluktuatif sehingga diperlukan kecukupan produksi untuk mendukung kestabilan harga. Kecukupan produksi dapat tercapai melalui pemanfaatan lahan marjinal seperti Ultisol yang masih luas dan perbaikan teknik budidaya, di antaranya melalui aplikasi pupuk Mikotricho. Tujuan penelitian adalah mengkaji pupuk Mikotricho dengan pengurangan dosis N-P-K terhadap pertumbuhan dan hasil bawang merah. Penelitian berupa percobaan lapang di lahan Ultisol menggunakan Rancangan Acak Kelompok Lengkap faktorial dengan tiga ulangan. Faktor pertama, dosis pupuk Mikotricho, yaitu 10 g, 30 g, dan 50 g/tanaman, faktor kedua, pengurangan dosis N-P-K berupa Urea, SP-36, KCl, dan ZA, yaitu 0, 25%, dan 50% dari rekomendasi. Hasil penelitian menunjukkan, aplikasi pupuk Mikotricho meningkatkan jumlah daun (11,4%) dan bobot tanaman segar (49,1%) bawang merah secara linier positif dengan dosis terbaik 50 g/tanaman. Hasil umbi/rumpun dan per petak efektif (0,64 m2) dosis pupuk Mikotricho, 10 g, 30 g, dan 50 g/tanaman tidak berbeda. Pengurangan dosis N-P-K dari rekomendasi berpengaruh terhadap jumlah anakan dan bobot segar tanaman bawang merah dengan efek linier negatif, namun pengurangan 25% dosis N-P-K dapat dipilih. Pengaruh interaksi pupuk Mikotricho dengan pengurangan dosis N-P-K terjadi pada kehijauan daun dan luas daun. Pemberian pupuk Mikotricho dosis 10 g hingga 30 g/tanaman dengan pengurangan dosis N-P-K 25% hingga 50% dari rekomendasi meningkatkan kehijauan daun dan luas daun bawang merah. Implikasi dari penelitian ini adalah diperlukan sosialisasi pemanfaatan pupuk Mikotricho pada budidaya tanaman bawang merah atau tanaman sayuran lain untuk mengurangi pemakaian pupuk sintetik dan perlu dukungan industri pembuatan pupuk Mikotricho.</p><p><strong>Keywords</strong></p><p>Mikoriza; <em>Trichoderma</em>; N-P-K; Bawang merah; Lahan marginal</p><p><strong>Abstract</strong></p><p>Shallots are a spice vegetable needed by the community. Adequacy of production can be achieved through the use of Ultisols with application of Mikotricho fertilizer. The aim of this research was to study the Mikotricho fertilizer with a reduced dose of N-P-K on growth and yield of shallots. The research was a factorial RCBD with three replications. The first factor, namely 10 g, 30 g, and 50 g/plant Mikotricho fertilizer dose, the second factor, namely 0, 25%, 50% N-P-K reduction of the recommendation.The results showed that Mikotricho fertilizer increased the number of leaves (11.4%) and fresh plant weight (49.1%) of shallots, the best dose of 50 g/plant. The yield bulbs/clump and per plot (0.64 m2) 10 g, 30 g, and 50 g Mikotricho fertilizer were not different. The 25% reduction in the N-P-K can be chosen to the number of tillers and fresh weight of shallots plants. Apply of Mikotricho fertilizer 10 g until 30 g/plant with a reduction in the N-P-K of 25% until 50% increases leaf greenish and leaf area. The implication was that socialization of Mikotricho fertilizer in cultivation of shallots or other vegetable crops to reduce the use of synthetic fertilizers and needs the support of the Mikotricho fertilizer manufacturing industry.</p>

scholarly journals Pengaruh Aplikasi Vermikompos terhadap Pertumbuhan, Kandungan Hara serta Hasil Tanaman Selada Hijau (Lactuca sativa L.) pada Budidaya Tanpa Tanah [Effect of Vermicompost Application on Growth, Nutrient Uptake, and Yield of Green Lettuce (Lactuca sativ)]

2021 ◽  
Vol 30 (2) ◽  
pp. 115
Author(s):  
NFN Nurhidayati ◽  
Masyhuri Machfudz ◽  
Nisma Ula Shoumi Rahmawati
Keyword(s):  
Nutrient Uptake ◽  
Block Design ◽  
Nutrient Content ◽  
Soilless Culture ◽  
Fresh Weight ◽  
Marketable Yield ◽  
Lactuca Sativa L ◽  
Randomized Block Design ◽  
Number Of Leaves ◽  
Solid Liquid

<p>Budidaya tanpa tanah pada dekade terakhir ini semakin berkembang seiring dengan munculnya beberapa permasalahan budidaya tanaman konvensional di lahan pertanian. Tujuan penelitian ini adalah menguji pengaruh aplikasi vermikompos padat dan cair terhadap pertumbuhan, kandungan hara, dan hasil tanaman selada hijau dengan jumlah tanaman per pot yang berbeda. Penelitian ini merupakan percobaan pot di rumah plastik yang menggunakan kultur substrat campuran cocopeat, zeolit, pasir dan vermikompos sebagai sumber nutrisi. Percobaan ini menggunakan Rancangan Acak Kelompok Faktorial. Faktor I adalah macam aplikasi vermikompos (padat, padat+cair,dan cair) dan Faktor II adalah jumlah tanaman per pot (satu, dua, dan tiga tanaman per pot). Hasil penelitian menunjukkan bahwa aplikasi vermikompos padat memberikan pertumbuhan tinggi tanaman (22,73 cm), jumlah daun (8,81), dan luas daun tanaman (974,76 cm2) tertinggi. Kandungan hara tertinggi terdapat pada aplikasi vermikompos padat dengan rata-rata masing-masing sebesar N= 4,39%, P=0,77% dan K=9,07%. Penanaman tiga tanaman per pot cenderung memberikan kandungan hara terendah pada ketiga metode aplikasi vermikompos. Namun, bobot segar biomassa dan hasil ekonomis tertinggi diperoleh pada aplikasi vermikompos padat dengan tiga tanaman per pot masing-masing sebesar 122,22 g dan 111,77 g. Hasil ini menunjukkan bahwa aplikasi vermikompos padat dan tiga tanaman per pot dapat disarankan untuk budidaya tanpa tanah tanaman selada hijau.</p><p><strong>Keywords</strong></p><p>Vermikompos; Pertumbuhan; Serapan hara; Hasil tanaman selada</p><p><strong>Abstract</strong></p><p>This study was a pot experiment in a plastic house using substrates culture and vermicompost as a source of plant nutrients. The purpose of this study was to test the effect of the application of vermicompost on growth, nutrient content and yield of green lettuce with different number of plants per pot. This experiment used a factorial randomized block design. The first factor was kinds of vermicompost application. The second factor was number of plant per pot. The research results showed that the application of solid vermicompost had the highest growth and nutrient uptake in plant height (22.73 cm), number of leaves (8.81) and leaf area (974.76 cm2) as well as an average of N = 4.39%, P = 0.77% and K = 9.07%. The treatments of solid+liquid vermicompost and liquid vermicompost alone, three plants per pot tend to provide the lowest nutrient uptake. However, the highest fresh weight of biomass and marketable yield was obtained in the application of solid vermicompost with three plants per pot by 122.22g and 111.77g, respectively. These results suggest that the application of solid vermicompost and three plants per pot is recommended in soilless culture for green lettuce plants.</p>

scholarly journals Efektivitas Nilai EC (Elektrical Conductivity) Terhadap Produksi Selada Merah (Lactuca sativa L.) Varietas Red Rapid Pada Sistem Hidroponik Rakit Apung.

2020 ◽  
Vol 8 (1) ◽  
pp. 1
Author(s):  
Rommy Andhika Laksono
Keyword(s):  
Electrical Conductivity ◽  
Lactuca Sativa ◽  
Block Design ◽  
Fresh Weight ◽  
Hydroponic System ◽  
Floating Raft ◽  
Lactuca Sativa L ◽  
Randomized Block Design ◽  
Number Of Leaves ◽  
Average Plant

This study aims to determine the effect of EC value (Electrical Conductivity) which is able to provide the best production of Red Lettuce (Lactuca sativa L.) Red Rapid Variety on the Floating Raft Hydroponic System. The experiment was conducted in a green house located in Sukaluyu Village, Telukjambe Timur District, Karawang Regency, from October to December 2016. The study used a randomized block design, consisting of 4 treatments, repeated 6 times, namely A (EC 0.5 - 1.5 mS / cm), B (EC 1.5 - 2.5 mS / cm), C (EC 2 , 5 - 3,5 mS / cm), D (EC 3,5 - 4,5 mS / cm) Data were analyzed using analysis of variance and further tests with Duncans multiple range test at 5% level. The number of plants for each treatment plot was 6 plants. The experimental results show that different EC (Electrical Conductivity) values have significantly different effects on the average plant height, 7, 14, 21, 28, 35 and 42 HST, the average number of leaves 21, 28, 35 and 42 HST , average stem diameter 7, 14, 21, 28, 35 and 42 days, average leaf area per plant, and average fresh weight per plant. The EC value of 3.5 - 4.5 mS / cm gives the highest production on the average fresh weight per lettuce plant (158.66 g), equivalent to 31.73 tons / ha. 

scholarly journals PENGARUH PENAMBAHAN KALIUM NITRAT DALAM LARUTAN HARA PADA MEDIA KASCING TERHADAP PERTUMBUHAN SELADA (Lactuca sativa L.)

AGRICA ◽  
2020 ◽  
Vol 6 (1) ◽  
pp. 53-62
Author(s):  
Hangrie Jemmy Namserna
Keyword(s):  
Electrical Conductivity ◽  
Nutrient Solution ◽  
Dry Weight ◽  
Potassium Nitrate ◽  
Treatment Level ◽  
Fresh Weight ◽  
Lettuce Plant ◽  
Shoot Tissue ◽  
Water Value ◽  
Shoot Weight

       This research was conducted with the aim to find out the effect of the addition of potassium nitrate in lettuce as a medium and critical level of concentration(electrical conductivity)of nutrient solution. Research is organized in the form of a pot experiment. The experimental design used was Complete RandomizedBlock Design (CRBD)) with three replications. The treatment consists of 12 levels of concentrations or nutrient solution electrical conductivity with the addition of potassium nitrate to lettuce plant. The treatment level of concentrations (conductivity) of nutrient is as follows; L0 = 0.00; L1 = 1.25; L2 = 2.50; L3 = 3.75; L4 = 5.00; L5 = 6.25; L6 = 7.50; L7 = 8.75; L8 = 10.00; L9 = 11.25; L10 = 12.50 and L1 = 13, 75 g 100 L-1 water. Value concentrations of electrical conductivity each nutrient solution concentrations are: L0 = 0.06; L1 = 0.26; L2 = 0.46; L3 = 0.66; L4 = 0.86; L5 = 1.06; L6 = 1.26; L7 = 1,46; L8 = 1.66; L9 = 1,86; L10 = 2.06 and L1 = 2.26. dS m-1. The result of the experiment showed that addition of KNO3 highly significant effect on the increase in fresh weight and dry weight of shoot per plant. Fresh weight and oven-dry weight of shoot per plant was significantly increased in a quadratic with increasing concentrations of KNO3are optimum for growth of plant shoot weight were at 12.23 g in 100/of water on electrical conductivity equivalent to 2.01 dS.m-1. The addition of concentration of KNO3to nutrient solution does not affect on N and other nutrient solution on shoot tissue of lettuce plant but the concentrations of P and K in plant shoot tissue were significantly increased linearly with the provision of KNO3.

scholarly journals Growth and development of lettuce plants at high NH4+:NO3- ratios in the nutrient solution

2006 ◽  
Vol 24 (3) ◽  
pp. 352-355 ◽  
Author(s):  
Jerônimo L Andriolo ◽  
Rodrigo dos S Godoi ◽  
Clarissa M Cogo ◽  
Orcial C Bortolotto ◽  
Gean L da Luz ◽  
...  
Keyword(s):  
Experimental Design ◽  
Nutrient Solution ◽  
Growth And Development ◽  
Crop Production ◽  
Dry Mass ◽  
Fresh Weight ◽  
Total N ◽  
Randomized Experimental Design ◽  
Number Of Leaves ◽  
Polynomial Models

Lettuce plants, cv. Vera, were grown at five NH4+:NO3- ratios in the nutrient solution in a 0.15 m deep sand growing bed. A standard nutrient solution was used, with the composition of, in mmol L-1, 11.0 NO3-; 1.5 H2PO4-; 6.5 SO4--; 7.5 Ca++; 10.0 K+ and 1.5 Mg++, and, in mg L-1, 0.42 Mn; 0.26 Zn; 0.05 Cu; 0.50 B; 0.04 Mo, and 4.82 chelate Fe. Ammonium nitrate was used to supply NH4+ concentrations of 2.5; 5; 7.5 and 10 mmol L-1, reaching NH4+:NO3- ratios of 0:11 (T1); 2.5:13.5 (T2); 5:16 (T3); 7.5:18.5 (T4) and 10:21 mmol L-1 (T5) as treatments. A completely randomized experimental design was used, with four replications and 20 plants per plot. Four plants of each plot were harvested at 25 days after planting, to determine shoot and root dry mass, shoot fresh weight and number of leaves per plant. Number of leaves, shoot fresh and shoot and root dry mass decreased 25.5%; 52.5% and 68.5% from T1 to T5, respectively, following polynomial models. Root dry mass was 1.7 g/plant for T1 and T2, and 0.82 g/plant for T3, T4 and T5, decreasing in a proportion of 51.8%. For lettuce crop production in hydroponical facilities, the NH4+ threshold limit of about 9-12% of the total N should be retained.

Sign in / Sign up

Export Citation Format

Share Document