Enhancing Biological Nitrogen Fixation In Pulse Crops Under Drought Condition.

Enhancing Biological Nitrogen Fixation In Pulse Crops Under Drought Condition.

Yaseen kanju

Introduction

• A process in which nitrogen gas (N2) from the

atmosphere is incorporated into the tissue of certain plants with the help of soil microorganisms.

• Conversion of atmospheric N2 into ammonium with the

help of soil microorganisms.

• Key entry point of molecular nitrogen into the biogeochemical cycle of nitrogen.

Biological nitrogen Fixation

Methods for enhancing symbiotic Nitrogen Fixation

Management practicesDifferent environmental factors affect the nitrogen fixation.

•Temperature.

•Moisture.

•Acidity.

•Chemical components e.g. nitrogen phosphorus.

NitrogenGenerally combined N delays or inhibits nodulation and nitrogen fixation.

Because of this adverse effect N fertilizer usually is not recommended for leguminous crops.

Nitrogen

• The fertilizer may affect nitrogen fixation of the legumes crops.

• Significant responses to 20-30 kg N/ha as starter dose have been observed under good growth.

Intercropping• Intercropping legumes with non-legumes is a

common cropping system in the tropics.

• The non legumes also affect the effectiveness of Nitrogen fixation of the legumes crops.

• Nitrogen fixation in fababean was affected by plant population ,density in sole or intercropping system with barley.

Cultural Practices• Mulching. • can control weeds and fluctuations of soil

moisture and temperature.• Liming. • can eliminate soil acidity, and Al and Mn

toxicities.

Tillage

• Nodulation and nitrogen fixation in Soybean grown in sub- tropical area were substantially improved under no tillage with N balance of 80 kg N/ha as compared with the cultivated system with 30 kg N/ha N balance.

• Clean cultivation accelerates the oxidation of

organic matter in soils and generally results in higher Nitrate in the profile.

Land form

• Mungbean ,Pigeon pea and Soybean grown on broad bed and furrows.

• Chickpeas sown on flat beds nodulated better

than sown on ridges.

• As ridges fields had greater evaporation losses due to increased surface area.

Land form

Other nutrients• In pigeonpea increased nodulation due to application

of DAP.

• Sodium molybdate significantly increased nodulation and grain yield.

• 1kg cobalt chloride increase 10 percent grain yield of

chickpea.

• 1kg sodium molybdate/ha increase 7 percent yield • 25 kg ZnSO4 /ha increase yield 4 percent.

Other nutrients

• Inoculation with Rhizobium increased yield of chickpea 26 percent.

• Inoculation along with Co, Mo and Zn application

increase yield 41 , 39 ,and 28 percent respectively.

Microbial Screening

• There are collections of effective rhizobia located at centers around in the world for most, if not all, legumes used in agriculture.

• These strains may be screened to identify the most effective and competitive one(s) for a given agroecosystem.

• Once strains have been identified, the legume under consideration is inoculated.

Microbial Screening

• Instructions on inoculant use are usually given by the manufacturers.

• Seed inoculation using peat inoculant is the most commonly used method.

• However, studies are under way to assess the effectiveness of post planting inoculation as a corrective measure Dual inoculation of rhizobia and mycorhizal fungi has proven beneficial in some cases.

Criteria for good inoculant strains• Effective nitrogen fixation over a range of

environmental conditions.• Competitive ability against other strains.• Ability to multiply .• Ability to migrate in soil and colonize it.• Ability to survive adverse environmental

conditions.• Nodule formation and nitrogen fixation in the

presence of soil nitrogen.

Molecular Biology Methods

1. Produce a genetic map of Rhizobium.

2. Develop genetically engineered Rhizobia .

3. Identify starins of Rhizobium by DNA probes or marker genes.