Hoaglands Medium; Ohne Stickstoff

Increasing energy security and mitigating climate change are the two main drivers that have pushed renewable energy generation to the top of the global agenda. They encourage agronomic production of biomass to meet renewable bioenergy needs.

• Perennial  grasses are attractive as biomass sources because they can meet the agronomic, environmental, and social requirements for successful use as energy crops.
• Perennial rhizome-like grass is an ideal biofuel crop because of its agronomically desirable traits of broad climate tolerance , rapid growth rates, and relatively high yields.  Additionally, perennial grasses have low nutrient requirements due to nutrient recycling through their rhizome systems . They are also rarely attacked by pests and can therefore be made with little or no pesticides .
• Given these unique advantages, interest in using biofuel crops for energy production is increasing. However, since China cannot afford to produce energy from biomass on its arable land, biofuel cultivation, in order to be competitive with conventional energy sources and avoid crowding out food crops, will likely be relegated to less productive soils and receive minimal water supply receive.
• Fertilizers and Pesticides. Therefore, peripheral areas can play an important role in the production of energy from biomass. It is estimated that the amount of marginal land that could be used for biofuel production in China is nearly 110 million hectares, of which about 45 million hectares would support economic operations. Abiotic pressures such as nutrient deficiencies, drought and high salinity in these areas are common factors limiting the production of biofuel crops.

Under environmental stress such as nitrogen (N) deficiency, which will be a major limiting factor for growing biofuel crops in Northwest and North China, plants show different adaptations at morphological, biochemical, molecular and physiological levels. It is imperative to update our knowledge of the tolerance of biofuel crops to various nutrient deficiency conditions to be expanded to allow continuous industrialization of biomass in peripheral areas. Efficient production of bioenergy from such marginal areas requires selection of the most stress-tolerant grass species. Biofuel crops are being screened or bred for superior traits and genetically modified for enhanced abiotic stress tolerance traits that will expand their acreage  [6] . Accordingly, it is desirable to assess the responses of promising biofuel crops to N-deficiency stress and to identify cultivars best suited for  biomass production  under N-deficiency conditions.

Switchgrass  (  Panicum virgatum  L.) is a warm season rhizome forming perennial  _C4  grass native to the North American tall grass prairies.

Because of its broad adaptability, rapid growth rate, ability to grow on low-productivity soils, and ability to function as a component in a multipurpose cropping system, it is a leading dedicated biofuel  feedstock candidate  in the United States. It reacts strongly to N fertilizers and is often drought tolerant. It can effectively sequester carbon in the soil and provides excellent cover for wildlife. With many beneficial traits as energy crops, the Department of Energy’s Bioenergy Feedstock Development Program (BFDP) decided to focus research on a model crop system and focus research resources on switchgrass to quickly realize its maximum yield as a  biomass  crop .

There are two distinct  ecotypes  of switchgrass:  lowland  tetraploid  and upland octoploid.

The lowland tetraploid ecotype originates primarily from the southern extent of the native range and the upland octoploid primarily from its mid-to-northern extent. Several dozen cultivated cultivars of each ecotype are commercially available, most of which are high-yielding selections from native populations. The species shows large differences in performance in relation to environmental variables, although lowland ecotypes typically produce larger yields than upland ecotypes.

Previous studies have mainly focused on the response of switchgrass biomass to N-nutrient suppl. The effect of N-deficiency on switchgrass has not been extensively studied, particularly in hydroponically cultivated seedlings, and knowledge of the effects of different levels of N-deficiency on agronomic traits  , photosynthetic parameters, and chlorophyll content in switchgrass is limited.

The aim of this study was to evaluate the performance and reproductive potential of six cultivars of the two ecotypes in response to N-deficiency stress and provide some theoretical basis for growing relatively high-yielding switchgrass on soils with low fertility and for breeding on high ones N content to create efficiency use.