Effects of seeding density and cultivar on productivity of baby spinach grown hydroponically in deep water culture systems

Effects

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of

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seeding

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density

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and

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cultivar

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on

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productivity

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of

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baby

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spinach

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grown

hydroponically

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in

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deep

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water

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culture

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systems

Daniel_​​Janeczko,_​​​Advisor:_​​​Dr._​​Michael_​​Timmons December,_​​2017

Cornell_​​University

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Abstract:_​​​Three_​​spinach_​​cultivars,_​​Carmel,_​​Space,_​​and_​​Seaside_​​(F1),_​​were_​evaluated_{​ ​​}in_​​regards_​​to

their_​​suitability_​​for_​​Deep_​​Water_​​Culture_​​(DWC)_​​hydroponic_​​production_​​according_​​to_​​the procedure_​​presented_​​in_​​Cornell_​​Controlled_​​Environment_​​Agriculture_​​(CEA)_​​Baby_​​Spinach Handbook._​​Carmel_​​consistently_​​had_​​the_​​highest_​sprout_{​ ​​}count_​​and_​produced_{​ ​​}the_​​highest_​​fresh weight_​​(FW)_​​among_​​the_​​three_​​cultivars._​​Space_​​performed_​​moderately_​​well;_​more_{​ ​​}data_​​is_​​needed for_​​statistical_​​robustness_​​and_​​verification_​​under_​​more_​​typical_​​higher-light_​​conditions._​​With_​​respect to_​​Carmel,_​​seeding_​​fewer_​​cells,_​​but_​​at_​​a_​higher_{​ ​​}reduced_​​sprouting_​​rate_​and_{​ ​​}yield,_​​but_​​not_​​severely. For_​​all_​​three_​​cultivars,_​​pericarps_​​(seed_​​coats_​​getting_​​stuck_​​on_​​cotyledons_​​time_​​of_​​harvest)_​​found_​​in manually_​​harvested_​​baby_​​spinach_​of_{​ ​​}marketable_​​size_​​were_​​rare.

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1._​​Introduction:

DWC_​​hydroponics_​​is_​the_{​ ​​}soilless_​​culture_​​of plants_​​whose_​​roots_​are_{​ ​​}immersed_​​in_​​a circulating,_​​aerated_​​nutrient_​​solution_​​that contains_​​all_​​necessary_​ions_{​ ​​}for_​​plant_​​growth, typically_​​practiced_​​in_​​ponds._​​Cornell_​​CEA has_​​worked_​​extensively_​​to_​​develop_​​a

production_​​protocol_​​for_​​all-year_​​DWC_​​baby spinach_​1​_.

Spinach_​​has_​​historically_​been_{​ ​​}a_​​difficult_​​crop to_​​grow_​​hydroponically,_​​especially

compared_​​to_​​lettuce,_​​for_​​several_​​reasons including:

(1)_​​Susceptibility_​​to_​​​Pythium_​​​infection, especially_​​​P._​​aphanidermatum_​​​and_​​​P. dissotocum_​3

(2)_​​Presence_​​of_​​pericarps_​​in_​​harvested product

(3)_​​Costly_​​labor_​inputs_{​ ​​}(seeding_​​&_​​harvest) Cornell_​​CEA,_​​Biological_​​&_​​Environmental Engineering_​​(BEE),_​​and_​​Element_​​Farms,_​​Inc. collaborated_​​to_​​evaluate_​​three_​​different cultivars_​​for_​​germination_​​and_​​grow_​​out potential_​​in_​​DWC_​​systems._​​Additionally, reliable_​​data_​​was_​gathered_{​ ​​}on_​​medium_​​usage per_​​flat_​​(when_​​filled_​​by_​​hand).

Experiments_​​were_​​performed_​​on_​​the_​​Ithaca campus_​​at_​​the_​Dimock_{​ ​​}Lab_​​and_​​Kenneth Post_​​Lab_​​House_​​where_​​the_​​flats_​​were_​​stored in_​​a_​​germination_​​chamber_​and_{​ ​​}grew_​​out_​​in_​​a bench-scale_​​DWC_​​system,_​​respectively.

This_​​work_​​builds_​​on_​​the_​​foundation_​​laid_​​by Cornell_​​CEA,_​​especially_​Drs._{​ ​​}D._​​de_​​Villiers, T._​​Shelford,_​​N._​Mattson,_{​ ​​}R._​​Langhans,_​​and L._​​Albright,_​​whose_​previous_{​ ​​}work_​​on_​​DWC hydroponics_​​and_​​spinach_​​production_​​made these_​​experiments_​​possible.

Summary_​​of_​​Recommended_​​Sowing Protocol:_​​​​The_​​Cornell_​​CEA_​​Hydroponic Baby_​​Spinach_​​Production_​​Handbook suggests_​​best_​​practices_​​for_​​sowing_​​spinach for_​​DWC_​​applications._​​Expanded

polystyrene_​​flats_​​are_​used_{​ ​​}with_​​common_​​cell configurations_​​of_​​13_​​cells_​by_{​ ​​}26_​​cells_​​on_​​1” centers._​​Speedling_​​and_​​Beaver_​​Plastic_​​flats are_​​the_​​most_​widely-used._{​ ​​}Flats_​​are_​​seeded according_​​to_​​a_​​three-step_​​protocol.

Figure_​​1:_​​​​Speedling_​​338_​​Flat

In_​​the_​​first_​​step,_​termed_{​ ​​}the_​​“first_​​pass”,_​​the flat_​​is_​​loosely_​​filled_​​with_​​pre-wet_​​medium_​​- ideally_​​a_​​sterile,_​​soilless_​​mix_​​-_​​and_​​scraped such_​​that_​​each_​​cell_​​is_​​evenly_​​filled_​​to_​​the_​​top. Then_​​the_​​flat_​​is_​​dibbled_​​using_​​the_​​tools described_​​in_​​the_​​following_​​sections._​​Next, the_​​tray_​​is_​​seeded_​with_{​ ​​}1-3_​​seeds_​​per_​​cell. Seeds_​​should_​​be_​dropped_{​ ​​}directly_​​in_​​the

center_​​of_​​cells._​​Finally,_​the_{​ ​​}flat_​​is_​​filled_​​with more_​​medium,_​​scraped,_​and_{​ ​​}dibbled_​​again_​​- this_​​time_​​with_​​a_​​shallower_​​dibbler._​​This_​​is the_​​“second_​​pass”._​After_{​ ​​}seeding,_​​flats_​​are stored_​​in_​​a_​high_{​ ​​}humidity_​​environment_​​with no_​​light,_​​after_​​which_​​they_​​are_​​floated_​​in production_​​ponds_​​until_​​harvest.

2._​​Materials_​​and_​​Methods:

Two_​​trials_​​were_​​conducted_​​comparing_​​the seeding_​​densities_​​and_​​cultivars._​​Experiments were_​​performed_​​in_​a_{​ ​​}dark_​​climate_​​controlled growth_​​chamber,_​​where_​​germination

occurred,_​​and_​​a_​​conventional_​​glass greenhouse_​​where_​​the_​​flats_​​grew_​​out_​​in_​​a bench-scale_​​DWC_​​system_​​with_​​typical hydroponic_​​nutrient_​​solution_​​as_​​suggested_​​by previous_​​Cornell_​​CEA_​​experiments.

2.1_​​​Germination_​​Chamber_​​and_​​Greenhouse Description:

Experiments_​​were_​​conducted_​​in_​​Ithaca,_​​NY (42◦26056.2”_​​N_​​76◦28008.3”_​​W).

Germination_​​occurred_​​in_​​a_​​climate

controlled_​​chamber_​​(10_​​ft_​2₎​ _{​​with​​no​​light​​and}

constant_​​temperature_​​of_​​24C.

Grow_​​out_​​occurred_​in_{​ ​​}a_​​conventional_​​glass greenhouse._​​The_​​DWC_​​system_​​was_​​located on_​​a_​​bench_​​in_​​the_​​NE_​​corner_​​of_​​the_​​room. Other_​​experiments_​​were_​​simultaneously conducted_​​on_​​other_​benches_{​ ​​}in_​​the_​​same room._​​As_​​such,_​no_{​ ​​}supplemental_​​light_​​was provided.

Grow_​​out_​​took_​​place_​in_{​ ​​}two_​​steel_​​tubs_​​(24” by_​​48”_​​by_​​12”)_​which_{​ ​​}fit_​​five_​​cut_​​flats (described_​​below)_​​when_​​completely_​​full. Nutrient_​​solution_​​flowed_​​freely_​​between_​​the two_​​channels_​​through_​​a_​​¾”_​​hose._​​Tubs_​​were insulated_​​with_​​¾_​in._{​ ​​}styrofoam_​​boards_​​on their_​​exterior_​​to_​minimize_{​ ​​}heat_​​transfer_​​and reduce_​​cooling_​​load.

A_​​1/6HP_​​submersible_​pump_{​ ​​}located_​​in_​​the corner_​​of_​​one_​​tub_​​drew_​​nutrient_​​solution_​​in from_​​both_​​tubs._​The_{​ ​​}solution_​​was_​​pumped through_​​a_​​venturi_​​air_​​injector,_​​followed_​​by_​​a ¼_​​HP_​​inline_​​chiller_​​that_​​kept_​​the_​​water temperature_​​at_​​19C._​Water_{​ ​​}was_​​returned_​​to the_​​tubs_​​through_​​1”_​​PVC.

In_​​addition_​​to_​the_{​ ​​}venturi_​​air_​​injector, dissolved_​​oxygen_​​(DO)_​​was_​​supplemented with_​​an_​​air_​​pump_​​(General_​​Hydroponics 110V,_​​8W)_​​attached_​to_{​ ​​}cylindrical_​​1”_​​air stones._​​Two_​​air_​​stones_​​were_​​placed_​​on_​​the bottom_​​of_​​each_​channel_{​ ​​}to_​​maintain_​​DO levels_​​close_​​to_​saturation._{​ ​​}DO_​​was_​​saturated as_​​checked_​​with_​​a_​​YSIPro20_​​DO_​​meter_​​(with galvanic_​​membrane)_​​when_​the_{​ ​​}system_​​was_​​at half-capacity.

Sections_​​of_​​the_​​tubs_​that_{​ ​​}did_​​not_​​have_​​flats covering_​​them_​​were_​​covered_​​with_​​styrofoam to_​​prevent_​​growth_​of_{​ ​​}algae_​​and_​​contaminants entering_​​the_​​water.

In_​​between_​​trials,_​the_{​ ​​}tubs_​​were_​​emptied, cleaned,_​​and_​​sanitized_​​with_​​Greenshield_​​to minimize_​​risk_​​of_​root_{​ ​​}infection_​​and_​​ensure consistent_​​nutrient_​​solution_​​conditions between_​​trials.

Figure_​​2:_​​Bench-Scale_​​DWC_​​System_​​at

half-_​​capacity

2.3_​​Nutrient_​​Solution_​​Conditions: The_​​stock_​​solutions_​​recommended_​​in_​​the Cornell_​​CEA_​​Baby_​​Spinach_​​Handbook_​​were prepared._​​The_​​day_​before_{​ ​​}the_​​flats_​​were removed_​​from_​​the_​​germination_​​chamber_​​for floating,_​​stock_​​solutions_​were_{​ ​​}added_​​to_​​RO water_​​in_​​the_​​tubs_​​in_​​a_​​1:1_​​ratio_​​(A:B)_​​to achieve_​​an_​​electrical_​​conductivity_​​(EC)_​​of 1200-1400uS/cm._​​This_​​naturally_​​maintained pH_​​between_​​5.7_​​and_​​6.3_​​without_​​the_​​addition of_​​any_​​additional_​​acid_​​or_​​base.

​​Over_​​the_​​course_​​of_​​each_​​trial_​​growout,_​​RO water_​​and_​​stock_​solutions_{​ ​​}were_​​added_​​to maintain_​​the_​​EC/pH_​within_{​ ​​}the_​​desired_​​range as_​​checked_​​by_​handheld_{​ ​​}meters,_​​calibrated_​​at the_​​beginning_​​of_​​every_​​trial,_​​every_​​two_​​days. Water_​​level_​​in_​​the_​​tubs_​​was_​​maintained_​​so that_​​growing_​​flats_​​were_​​not_​​shaded_​​by_​​the tub_​​walls.

2.4_​​Greenhouse_​​Abiotic_​​Conditions: Greenhouse_​​ambient_​​temperature_​​was maintained_​​at_​​24C_​from_{​ ​​}8am-8pm_​​and_​​19C at_​​night_​​by_​an_{​ ​​}automated_​​Argus_​​system. The_​​greenhouse,_​​which_​is_{​ ​​}a_​​relatively_​​new, clean_​​structure_​​has_​a_{​ ​​}transmissivity_​​of_​​about 85%._​​The_​​DLI_​​average_​​in_​​the_​​greenhouse_​​for each_​​trial_​​is_​estimated_{​ ​​}from_​​outside_​​light records,_​​these_​​transmissivity_​​values,_​​and shade_​​curtain_​​position._​​The_​​results_​​are reported_​​in_​​the_​appendix._{​ ​​}Given_​​light_​​was not_​​regulated_​​between_​​trials,_​​it_​​is_​​improper_​​to compare_​​directly_​​across_​​trials.

2.5_​​Flats_​:

Speedling_​​338_​​flats_​​were_​​used_​​for_​​all_​​trials. The_​​26_​​row_​​flats_​​were_​​cut_​​to_​​22_​​rows_​​in

order_​​to_​​fit_​​tightly_​in_{​ ​​}the_​​channels._​​Halves_​​of these_​​cut_​​flats_​were_{​ ​​}considered_​​for_​​different treatments_​​and_​​are_​​comprised_​​of_​​10_​​rows_​​by 13_​​cells_​​per_​​row,_​​or_​​130_​​cells_​​total,_​​with_​​two rows_​​separating_​​the_​​respective_​​halves_​​which were_​​filled_​​with_​medium,_{​ ​​}but_​​not_​​seeded. Cells_​​are_​​rectangular_​​on_​​the_​​top,_​​spaced_​​on one-inch_​​centers_​​and_​tapered_{​ ​​}to_​​a_​​circular hole_​​on_​​the_​​bottom._​​The_​​cut_​​flats_​​had dimensions_​​of_​​13.5”_​by_{​ ​​}22.5”_​​by_​​1.75”. 2.6_​​Dibbling_​​Tools:

A_​​combination_​​of_​​conventionally_​​built_​​and 3D-printed_​​dibbling_​​tools_​​were_​​used_​​for these_​​experiments._​​Conventionally_​​built dibblers_​​constructed_​​are_​​described_​​in_​​the CEA_​​Spinach_​​Production_​​System_​​Report:

“To_​​control_​​depth_​of_{​ ​​}seeding_​​precisely_​​and firm_​​the_​​medium_​​above_​​the_​​seed

uniformly,_​​two_​​dibbling_​​tools_​​were_​​made for_​​each_​​type_​​of_​​flat_​​used._​​The_​​first

compressed_​​the_​​medium_​​in_​​the_​​cell_​​by_​​5/16 inches._​​After_​​seeding_​​and_​​covering_​​with additional_​​medium,_​​the_​medium_{​ ​​}in_​​the_​​cell was_​​again_​​compressed,_​this_{​ ​​}time_​​by_​​¼ inch._​​The_​​purpose_​of_{​ ​​}covering_​​seed_​​and firming_​​the_​​medium_​above_{​ ​​}it_​​is_​​to encourage_​​roots_​​to_​​penetrate_​​downwards rather_​​than_​​popping_​out_{​ ​​}of_​​the_​​soil. Compression_​​of_​​the_​​medium_​​above_​​and below_​​the_​​seed_​​was_​​quite_​​light,_​​and_​​depth of_​​seeds_​​not_​​great,_​​in_​​both_​​cases_​​just enough_​​to_​​eliminate_​“pop-ups”_{​ ​​}as_​​a_​​serious problem,_​​while_​​not_​​impeding_​​root

penetration_​​or_​​shoot_​emergence._{​ ​​}Use_​​of_​​a standardized_​​procedure_​​and_​​special_​​tools

ensured_​​uniformity_​​of_​​conditions_​​seed_​​to seed,_​​and_​​repeatability_​​across_​​experiments. Questions_​​as_​​to_​ideal_{​ ​​}degree_​​of_​​soil

compression_​​above_​​and_​​below_​​the_​​seed were_​​not_​​systematically_​​investigated experimentally,_​​but_​​were_​​determined_​​by trial_​​and_​​error_​​and_​​recourse_​​to

experience._​2​_”

Figure_​​3:_​​First_​​pass_​​plate_​​dibbler

Olav_​​Imsdahl_​​(BS/M.Eng_​​Mechanical_​​Eng., Cornell_​​2017),_​​designed_​​and_​​3D-printed rolling_​​dibblers_​​from_​ABS_{​ ​​}polymer_​​at_​​the Rapid_​​Prototyping_​​Lab_​​on_​​Cornell’s_​​Ithaca campus._​​The_​​individually_​​printed_​​pieces were_​​bolted_​​together,_​​as_​​shown._​​The 3D-printed_​​dibbler_​​worked_​​well_​​for_​​the second_​​pass,_​​as_​the_{​ ​​}protruding_​​points_​​are shallower,_​​which_​​allowed_​it_{​ ​​}to_​​roll_​​easily across_​​the_​​flat_​surface,_{​ ​​}resulting_​​in_​​consistent compression_​​and_​​time_​​savings_​​when

compared_​​to_​​use_​​of_​​wooden_​​single-row dibblers.

Given_​​the_​​similar_​performance_{​ ​​}of_​​the_​​cells that_​​had_​​been_​​dibbled_​​with_​​the_​​wooden_​​and 3D-printed_​​rolling_​​dibblers_​in_{​ ​​}a_​​prior_​​test run,_​​the_​​3D-printed_​rolling_{​ ​​}dibbler_​​was_​​used in_​​these_​​experiments.

At_​​the_​​radius_​considered,_{​ ​​}deeper_​​first_​​pass printed_​​dibblers_​​did_​​not_​​roll_​​easily_​​across_​​the

flat_​​surface,_​​and_​instead_{​ ​​}the_​​plate_​​dibbler pictured_​​in_​​​Figure_​​3_​​​was_​​used_​​in_​​all experiments_​​for_​​the_​​first_​​pass.

Figure_​​4:_​​Single_​3D_{​ ​​}printed_​​roller_​​(left);

whole_​​flat_​​roller_​​with_​​dowel_​​for_​​a_​​handle

(top);_​​wooden_​​dibbler_​​&_​​forceps_​​for

handling_​​seeds_​​(bottom)

2.8_​​Seeds

All_​​seeds_​​tested_​were_{​ ​​}procured_​​from_​​Jonny’s Seeds_​​Inc._​​and_​were_{​ ​​}ordered_​​in_​​September 2017._​​When_​​not_​​in_​​use,_​​they_​​were_​​stored_​​in_​​a cool,_​​dry_​​environment_​in_{​ ​​}the_​​headhouse._​​The reported_​​germination_​​rates_​​are:_​​Carmel_​​- 84%,_​​Seaside_​​-_​97%,_{​ ​​}Space_​​-_​​99%.

Figure_​​5:_​​Seed_​packets_{​ ​​}with_​​reported_​​rate

2.9_​​Sowing,_​​Germination,_​​and_​​Floating Procedure:

The_​​recommended_​​procedure_​​from_​​CEA_​​was followed_​​closely._​​Before_​​seeding,_​​flats_​​were cleaned_​​of_​​soil/debris,_​​disinfected_​​with_​​a Greenshield_​​solution,_​​thoroughly_​​rinsed_​​to remove_​​any_​​residue,_​and_{​ ​​}allowed_​​to_​​dry. Sungro_​​Propagation_​​mix,_​​composed_​​of sphagnum_​​peat_​​moss,_​​horticultural_​​perlite, horticultural_​​vermiculite,_​​wetting_​​agent,_​​and starter_​​nutrients_​​was_​​used._​​RO_​​was_​​added_​​to the_​​dry_​​medium_​​at_​​​a_​​ratio_​​of_​​0.6kg_​​RO_​​water per_​​1_​​kg_​​dry_​​medium_​​and_​​mixed_​​in

five-gallon_​​buckets._​​This_​​moisture_​​content was_​​chosen_​​given_​​the_​trial_{​ ​​}run_​​results_​​and_​​the fact_​​that_​​the_​​dry_​medium_{​ ​​}was_​​easier_​​to_​​work with_​​and_​​stuck_​​to_​​the_​​dibbler_​​less._​​The medium_​​and_​​water_​were_{​ ​​}well-mixed,_​​and_​​the lid_​​was_​​kept_​​on_​​the_​​buckets_​​except_​​when mixing_​​or_​​filling_​flats_{​ ​​}to_​​mitigate_​​moisture loss.

When_​​filling_​​the_​​flats_​​for_​​the_​​first_​​pass,_​​a_​​¼” metal_​​mesh_​​screen_​​was_​used_{​ ​​}as_​​a_​​sieve_​​to remove_​​any_​​clumps_​from_{​ ​​}the_​​medium_​​and ensure_​​homogenous,_​​loosely-packed_​​filling of_​​cells._​​Excess_​​medium_​​was_​​scraped_​​off_​​the top_​​of_​​the_​​flat_​​with_​​a_​​straight_​​edge._​​The_​​plate dibbler_​​was_​​used_​to_{​ ​​}create_​​consistent_​​dibbles in_​​each_​​cell._​Subsequently,_{​ ​​}flats_​​were_​​seeded at_​​the_​​appropriate_​​density.

Figure_​​6:_​​Metal_​​mesh_​​sieve

Post-seeding,_​​another_​​layer_​​of_​​medium_​​was added_​​on_​​top_​​of_​​the_​​seeds,_​​following_​​the same_​​sieving_​​procedure_​​described_​​for_​​the first_​​pass._​​Finally,_​the_{​ ​​}rolling_​​dibbler_​​was used_​​to_​​compress_​​the_​medium_{​ ​​}on_​​top_​​of_​​the seeds_​​in_​​the_​​second_​​pass_​​by_​​rolling_​​the dibbler_​​across_​​the_​​flat_​​surface_​​back_​​and_​​forth several_​​times.

Once_​​all_​​flats_​were_{​ ​​}seeded,_​​filled,_​​and dibbled_​​they_​​were_​​stacked_​​randomly. Non-seeded_​​guard_​​flats_​were_{​ ​​}placed_​​on_​​the top_​​and_​​bottom_​​of_​the_{​ ​​}stack._​​The_​​entire_​​stack of_​​six-seven_​​flats_​was_{​ ​​}wrapped_​​in_​​PVC plastic_​​wrap_​​to_​prevent_{​ ​​}moisture_​​loss._​​The stack_​​was_​​moved_​​into_​​a_​​larger,_​​rigid_​​plastic bin_​​for_​​transportation_​​to_​​the_​​germination chamber,_​​where_​​the_​​flats_​​were_​​stored_​​for_​​60 hours_​​in_​​the_​​dark_​at_{​ ​​}24C_​​before_​​removal_​​for inspection_​​and_​​floating.

Figure_​​7:_​​Flats_​​just_​​after_​​floating

Upon_​​removal_​​from_​​the_​​germination chamber,_​​flats_​​were_​inspected_{​ ​​}for_​​pests_​​and abnormalities._​​Throughout_​​the_​​experiment, no_​​pests_​​were_​found_{​ ​​}in_​​seedlings._​​All germinations_​​appeared_​​successful_​​upon removal_​​from_​​the_​chamber_{​ ​​}-_​​meaning_​​there were_​​some_​​visible_​​sprouts_​​protruding_​​from the_​​medium_​​and_​many_{​ ​​}more_​​young_​​roots protruding_​​out_​​of_​​the_​​bottoms_​​of_​​flats._​​After this_​​step,_​​the_​​flats_​​were_​​carefully_​​floated_​​in the_​​tubs,_​​where_​they_{​ ​​}remained_​​until_​​removal for_​​harvest.

2.10_​​Seedling_​​Sprout_​​Count:

On_​​the_​​sixth_​​day_​after_{​ ​​}flotation_​​in_​​the_​​tubs, the_​​total_​​visible_​​seedling_​​sprouts_​​were counted_​​for_​​each_​​treatment._​​This_​​count included_​​“popups”_​​(sprouts_​​that_​​withered because_​​their_​​roots_​​did_​​not_​​reach_​​the_​​water), which_​​were_​​uncommon._​​Earlier_​​sprout counts_​​were_​​performed_​​in_​​the_​​first_​​trial,_​​and found_​​to_​​be_​​a_​poor_{​ ​​}indication_​​of_​​the_​​final number_​​of_​​seedlings_​present_{​ ​​}at_​​time_​​of harvest.

2.11_​​Harvesting_​​Protocol:

Flats_​​were_​​harvested_​​when_​​the_​​fastest growing_​​treatment’s_​​leaves_​​reached

marketable_​​size,_​​which_​​occurred_​​between_​​14 and_​​16_​​days_​​after_​flotation_{​ ​​}in_​​the_​​tubs._​​This designation_​​was_​​subjective_​​between_​​trials, but_​​for_​​each_​​case_​​determined_​​by_​​the_​​larger leaves_​​of_​​the_​​Carmel_​​treatments._​​Leaves were_​​not_​​allowed_​​to_​get_{​ ​​}longer_​​than_​​3”_​​in length_​​before_​​harvest,_​which_{​ ​​}was_​​the_​​ceiling for_​​leaf_​​size_​​and_​​provides_​​a_​​point_​​of

reference.

Figure_​​8:_​​Close_​Up_{​ ​​}of_​​Harvested_​​Flat

Harvesting_​​was_​​performed_​​by_​​hand_​​with scissors._​​A_​​handful_​of_{​ ​​}leaves_​​would_​​be carefully_​​grasped_​​from_​the_{​ ​​}top._​​The_​​stems would_​​then_​​be_​​cut_​​about_​​halfway_​​down_​​the stems_​​of_​​the_​​longest_​​leaves._​​This_​​meant_​​the smaller,_​​shorter_​​leaves_​from_{​ ​​}each_​​flat_​​were also_​​harvested_​​with_​shorter_{​ ​​}stems,_​​since_​​they were_​​lower_​​in_​​the_​​canopy._​​A_​​large_​​variance in_​​leaf_​​size_​​was_​​found_​​for_​​all_​​treatments,

which_​​was_​​due_​both_{​ ​​}to_​​the_​​non-simultaneous germination_​​observed,_​​and_​​the_​​presence_​​of young,_​​second_​​true_​​leaves_​​in_​​addition_​​to_​​the older,_​​larger,_​​first_​​true_​​leaves._​​Harvest weight_​​(as_​​well_​as_{​ ​​}medium_​​usage)_​​was measured_​​with_​​a_​20lb_{​ ​​}digital_​​scale_​​accurate to_​​one_​​gram_​directly_{​ ​​}after_​​leaves_​​were harvested._​​As_​​can_​​be_​seen_{​ ​​}in_​​Figure_​​8,_​​many small_​​leaves_​​go_​​unharvested.

2.11_​​Trial_​​Timeline

Seeding_​​Density_​​Trial

Seed:_​​10/11 Float:_​​10/13 Harvest:_​​10/28

Cultivar_​​Comparison_​​Trial

Seed:_​​10/28 Float:_​​10/30 Harvest:_​​11/17

2.12_​​Statistical_​​Analysis

The_​​statistical_​​analysis_​was_{​ ​​}the_​​same_​​for each_​​trial._​​The_​​average_​​and_​​standard deviation_​​of_​​each_​​treatment_​​was_​​calculated for_​​both_​​final_​​sprouts_​​and_​​fresh_​​weight_​​- except_​​Space,_​​for_​​which_​​only_​​one_​​flat_​​was seeded.

The_​​results_​​from_​​one_​​well-germinating_​​flat chosen_​​as_​​a_​representative_{​ ​​}sample_​​are_​​also reported_​​to_​​show_​​the_​​intra-flat_​​variation_​​to_​​be expected,_​​even_​​when_​germination_{​ ​​}occurs_​​at_​​a high-percentage_​​of_​​the_​​reported_​​rate.