Alfalfa

Overview

Alfalfa - Foreword

Alfalfa is considered the excellence legume forage crop all around the world. Productivity, longevity, easy processing and conservation, nutritional value of fodder and hay and positive action on structure and fertility of soil make Alfalfa the most important legume forage crop. Alfalfa can be used as hay, silage, pasture (together with other forage grasses plants) and dehydrated flour or pellet as protein concentrate for cattle.


Plant Stages and Environment Requirements

Alfalfa is a legume perennial plant, with a powerful root system which can reach several meters in depth, stems are 90-100 centimeters tall and they sprout from the basal portion of the plant (crown). Leaves are trifoliate, flowers are united in racemes, color is from violet to yellow, fruits are pods spiral-like. Seeds are yellow brownish, very small, about 500 seeds in a gram. Main growth stages are: Germination, is a biochemical process by which reserve compounds as sugars and proteins are transferred from cotyledons to embryo, which evolves in seedling: cotyledons, as in all legume, are pulled out of soil. First knot is formed above cotyledons and then the first leaf appears. At this stage, the plant begins photosynthesis and is not more dependent on seeds reserves. Moisture and water are critical for germination as well as a proper soil texture in order to avoid crust formation, which hinder the emergence of cotyledons out of soil. Vegetative growth Defined below are the stages of Alfalfa growth (adapted from Alfalfa Management /Diagnostic Guide, 1990, Pioneer Hi-Breed International).


Crop Rotation and Nitrogen Synthesis

Alfalfa can be grown in rotation with any crop except Sugar Beet
- Winter wheat grows well in rotation with Alfalfa
- It is not recommended to grow Sugar beet after Alfalfa as it can cause ryzoctonia.
Monoculture is to be avoided, because symbiosis with Rhizobium bacteria and pest attacks can reduce yield and plant population.
Rhizobium bacteria, present on well-nodulated Alfalfa, can create enough nitrogen to meet the needs of the growing Alfalfa crop. Until nodulation occurs, however, Alfalfa seedlings depend on available soil nitrogen for growth (Rhizobium Melitoti).
Alfalfa residue improves the organic matter and Nitrogen content of soil.
Alfalfa lasts from 5 to 8 years.
No tillage required decreasing operational costs and soil compaction while increasing the soil structure improves.
Weed control is very effective due to the continuous cuttings for harvesting the crop.


Conventional Tillage

• Tillage for alfalfa is carried out in very different ways, depending on timeliness, region and soil structure. However, we must remember that seeds are extremely small, germination phase is the most critical for the crop and ponding is detrimental. For spring drilling, best season for primary tillage is previous autumn in order to allow wintering of soil and building of a fine texture.
A perfect Alfalfa seedbed should have 4 Fs:
- Firm to reduce air pockets
- Fine to obtain an even covering of seed,
- Flat with no places where water stands
- Free from weeds that compete with seedlings for moisture and plant nutrients. Seedbed preparation is costly, time-consuming, and can reduce valuable soil moisture.
In conventional tillage
- Ploughing is performed at about 30-50cm of depth
- Ripping at about 50cm is mandatory where hard pan exists.
Seedbed preparation is carried out with field cultivators, power harrows, disk harrows or spike harrows in order to obtain a proper sizing of clods, which is crucial, because seeds are very thin. Clods must be less than 2cm in diameter to provide proper soil-seed contact.


Drilling

Drilling Periods
- Spring Seeding starts from 15th of March up to mid May, depending on local climate. Minimal soil temperature is 8-10°C.
- Summer Seeding is carried out after the harvesting of wheat, up to early September.
Row spacing between 13 and 25cm.
2cm is the Maximum Depth for small-seeded legumes like Alfalfa. Small seeds are often unable to emerge from deep plantings.
Planting rates vary between 20 to 40kg/ha, because not all seeds germinate and emerge (average 50%). Despite high loss rate, high population is recommended to ensure adequate stands.
After drilling packing of soil is needed.
The goal is to achieve an ideal 500 stems per square meter.


Fertilization

Alfalfa responds well to liming, being very sensitive to acidity of soil. Once Alfalfa is established, there is no opportunity to incorporate lime.
Alfalfa responds very well to fertilization with phosphorus and potassium. Because Alfalfa is a forage crop normally harvested three to five times during the growing season, when nutrient removal can be very high.
• N should be no concern, because bacteria Rhizobium meliloti present on well-nodulated Alfalfa, can synthetize enough Nitrogen to meet the needs of the growing Alfalfa crop. Until nodulation occurs, however, Alfalfa seedlings depend on available soil nitrogen for growth. P and K fertilizers can be applied in spring or/ and after each cut. Chart below can serve as guideline for needed quantities of fertilizers based on hay production. As for all crops, soil test prior to Alfalfa establishment is essential to determine lime and fertilizer needs. Soil tests should be taken well before seeding, usually during summer and fall, to allow time for incorporation of lime and base fertilizers into the soil.
• If soils are clayish and heavy, then it is possible also to incorporate Phosphorus and Potash during the tillage before the drilling of the crop. The whole rate of P can be incorporated during the tillage. Concerning K, it is possible to incorporate the whole rate during tillage in heavy soils, or spread the annual rate of K after winter in light soils.


Irrigation

Alfalfa is a deep-rooted, drought-tolerant perennial with a long growing season. In deep, well-aerated soil, roots may extend down to 3 meters. For maximum yields, however, it also is a large water user with seasonal water use in excess of 1.000 millimeters per season, or from 9.000 to 14.000 cubic meters per hectare; in other words, the average seasonal water need for Alfalfa is about 24 millimeters per hectare per ton of product.


Weed Control

More common weeds in Alfalfa fields are annual dicotyledons (lambsquarter, morninglory, pigweed) grasses and also perennial dicoyledons as histle.

Alfalfa seedling are not competitive with weeds, when good stand of Alfalfa are very competitive, therefore a complete control of weeds before the planting and during the establishment of the crop is crucial. Many herbicides are available for pre-planting and post emergence treatments.


Cutting

First cutting has to be decided on the basis of crown buds development.
Subsequent cuttings are made when 10-15% of plants are blooming.
• Later cuttings often produce forage that has lower yield, nutrients, and overall quality.
In order to reduce losses of leaves, cutting height can be also lower than 13cm and swathing better carried out when moisture of bulk is about 25/30%.
• To maintain replenishment of root reserves, make sure that there is at least 20-30cm of foliage or 4 to 6 weeks of growth time before the average first freeze date.


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