Pan-African Soybean Variety Trial Protocol Training
The protocol Outlines Site selection Land preparation Soil sampling Experimental layout Methods of planting Fertilizer application
Site selection Use the following criteria to select land for field Experiment: When selecting land for field experiment consider the land terrain, soil type, weather and also the pest and disease factors. Select well-drained, fertile loamy soils with good water retention capacity Select land with uniform soil with little or no slope, where flooding, run-off, and erosion are minimal Select land fully exposed to sunlight avoid shady areas like those near forest trees Avoid sandy soil that easily drain out to avoid drought stress Avoid clay soil that easily compact into a hard mass which inhibits germination Access to a good road is a plus so that locations could be used for a field day.
Land preparation Good land preparation involves clearing, ploughing and harrowing ----- the fields should be properly tilled to incorporate plant residues and conserve water Land should be prepared in accordance with the chosen soybean planting pattern: On flat seed beds; the land should be ploughed and harrowed properly Good land preparation should:- provide deep rooting and a moist seedbed for planting. create good contact between the seed and soil which enhances rapid germination and reduces weed infestation.
Why is soil sampling necessary? Soil sampling is necessary to determine the levels of essential nutrient for plant uptake to make informed decisions related to right soil amendments such as fertilizer ( accurate fertilizer recommendation) Materials for soil sampling Hand held Auger/probe/straight shovel Tube samplers Buckets Permanent markers Sealable plastic bags Note that all sampling equipment should be made up of stainless steel or plastic avoid using painted surfaces
Methods of soil sampling Soil sampling should be done when soil are at field capacity to ensure penetration and prevent soil from smearing during sampling Soil Sampling Procedures it is essential to divide experimental fields into smaller uniform sampling units because soil variation occurs as a result of parent materials, soil texture, topography and nutrient removal by plants Sample Depth. The normal sampling depth for nutrients is about 15 cm because most plant roots grow to that depth, and tillage mixes most nutrients into the soil to about 15 cm deep. Subsoil is normally much lower in nutrient content, so sampling too deep will produce a sample that is not representative of the field.
Sample collection using an auger Once the sampling areas are determined, a representative samples must be collected randomly from the entire sample units to avoid the risk that a non-representative sample could skew the results The most efficient way to achieve random sampling is to follow a zig-zag pattern around the field Shovel or spade can be used for soil sampling, however, it is more efficient to use a sampling probe or auger Once the sampling units are decided, remove any surface organic litter as it may skew the nutrient analysis and drill hole to the required depth using the auger.
Soil Sampling procedures Slowly and carefully removed the soil auger with the soil samples after reaching the desired depth Carefully remove the soil samples after the auger has been removed from the hole Collect at least 10 to 15 samples at a depth of 15 cm from each sampling unit Mix all the samples from all the sampling units to create a composite sample - remove foreign materials like roots, stones, pebbles and gravels Transfer the sample into a clean cloth or sealable polythene bags- avoid galvanized pail Label the bag with relevant information and coding Air-dry soil samples in the room overnight and take subsample for analysis
Experimental Field Layout Materials: Measuring tape, rope and pegs. Design of the experiment: select the most appropriate design make a plan of the experiment, keeping in mind the slope and all known variations in the experimental area Arrange the replications to minimize the variations within replications The field plan should include the following: experimental design, treatment and number of replications Number of plots in the experiment Plot size (length x breadth) Border areas for the experiment The arrangement of the plots and blocks Randomization of treatments and replications
Procedures for field layout: Construct a straight line by fixing a peg on the first row of the first plot Form a right-angle triangle with the tape and fix two stakes perpendicular to each other Extend the two sides to the required length of the experiment by your eye-line. Measure and peg to indicate the blocks according to the plan Leave required alleyways between blocks Measure and peg the individual plots according to the plan Check for the correctness of all the measurement by counting the plots and by checking the diagonals Tie tags on a stake for the first row of each plot, from left to right when facing the field----- the tags must indicate plot number replication number
Methods of planting: flat field should be ploughed and harrowed properly Wait for consistent rains and good soil moisture before planting Plant on the well-levelled fields Inoculate seed with rhizobium prior to planting Plant spacing and seeding rate: When planting on flat seed bed, place one seed per plant station at a spacing of 50 cm between rows and 5 cm between plants to a depth of 2-3cm. Good seed-to-soil contact must be ensured for good emergence Do not sow seeds more than 2 5 cm deep as deeper planting may result in loss of vigor or failure of seedlings to emerge The greater the uniformity in planting depth, the better your chance to optimize stand establishment and maximize yield.
Fertilizer application Procedures: The use of fertilizer at sowing provides the seedling with the major nutrients required in the early stages of development A good fertilizer recommendation for soybean production depends on a good soil test At planting or one week after planting, apply phosphorus using 2 50 kg bags for hectare of 23:21:0 +4S compound fertilizer available in Malawi. Note that heavy supply of nitrogen fertilizer causes inhibition of nodulation and nitrogen fixation Open the furrows with hand trowel a little deeper than the sowing depth Distribute the calculated amount of fertilizer uniformly in a band, one replication at a time Complete each fertilizer application, replication by replication ------do not apply fertilizer across replications
Harvesting Soybean matures within 3 4 months after planting and requires timely harvesting to avoid yield losses due shattering Harvesting should be done in the morning when the temperature is still low to avoid shattering. Do not harvest on a rainy day to avoid drying problems which can lead to sprouts and rots. Signs of maturity in soybeans: Leaves will turn yellow then brown and fall to the ground. 90-100% of pods have turned brown and dry, but before they are brittle and shatter. At harvest, the seeds usually contain about 14% moisture Do not uproot soybean during harvesting, harvest from the base to allow root to decompose into the soil
Data collection procedures Germination percentage will be determined by counting the number of seed that germinated per net plot The number of days to 50% flowering will be determined when 50% of the plants have flowered Days to physiological maturity and plant height will be determined when 85% of individuals per cultivar have matured Above ground biomass will be oven dried at 60 ºC and 24 hours and weight using a standard balance scale Seed yield will be determined in kilograms during harvest from the middle rows of each plot Plot yield will be converted to kg/ha The weight of 100 seed will be determined in grams from randomly selected seeds after harvest Temperature and rainfall will be recorded from the nearest meteorological stations of each location.