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Farmers know about inoculants.

Byline: Zubair Aslam and Qamar uz Zaman

Inoculants usually known as "Microbial inoculants" or "Soil inoculants" are agricultural amendments that use beneficial rhizosphere microbes to promote plant health. These live microbes form symbiotic relationships with the target crop plants benefitting both parties. These microbes residing in the nodules on the roots of leguminous crops are responsible for fixing nitrogen. The application of the inoculants is little bit tricky and training demanding to maximize the nitrogen delivered especially when using in dry sowing, in acidic soils and when applying the fertilizers and pesticides.

The inoculation of legumes with rhizobia has become an important practice to increase the nitrogen fixation and improve the soil fertility. The fixed nitrogen can be used later by both leguminous as well as non-leguminous crops. There are certain considerations which need to be addressed before applying inoculants which are soil type, legume species and inoculation history like sowing of new crops first time in some soils. We also need to check the compatibility between the rhizobial inoculants, fertilizer and seed applied pesticides additives.

BENEFITS OF N2-FIXATION/NEED OF THE INOCULANTS

It is estimated that legume crops and pastures can fix almost three million tons of the nitrogen in a year (Ryder and Denton, 2014). It can cover 50 per cent requirement of the nitrogen that is needed annually for grain and animal production. However, the contributions made by the legumes may vary considerably with population of the species and with the situation (soil type, seasonal rainfall and crop management and some other unknown factors). It has been recorded that crop legume can fix nitrogen, on an average 110 kg nitrogen ha-1 annually. However, the range is large, and it is about zero to more than 400 kg of N/ha depending upon the many factors. Crop biomass has great effect on the nitrogen fixation which can be increased with good agronomic management practices. Management practices that optimize water use efficiency and keep soil nitrate levels low will favor legume growth and nitrogen fixation.

WHEN TO APPLY, WHERE TO APPLY AND HOW TO APPLY INOCULANTS

There is a great chance of good response to grain legume or pasture inoculation where there has been first time cultivation of the legume crop in history. It is recommended that there should be inoculation every four years or so will be adequate because soil rhizobial population will generally be maintained. After four years there may be more response to inoculation because lower numbers of rhizobia will remain in the soil, so a soil top layer with the potent commercial inoculation strain may be more beneficial. If there are acid sensitive legumes, then there may be need to inoculate every year because rhizobial population tends to diminish quickly under this soil condition.

There is exception to this acid rule for lupines because both lupines and their rhizobial strain are well adapted to acidic soils. To check the efficiency of the inoculation on any legume crop is not difficult and it can be checked in the comparison study of inoculated and non-inoculated of the same species of crop and see the difference of the number of nodules and their distribution on the root as well as careful breaking open nodules will reveal if they are pink or reddish colour showing that nodules are active; whereas green or white nodules are inactive.

ESTIMATES OF THE AMOUNTS OF N FIXED ANNUALLY BY CROP LEGUMES

Legume###% of crop N###Shoot dry###Shoot N (Kg)###Root N (Kg)###Total crop N###Total N fixed

###requirement###matter###(Kg)###(Kg)

###fixed

Lupins###75###5.0###125###51###176###130

Peas###66###4.8###115###47###162###105

Faba beans###65###4.3###122###50###172###110

Lentils###60###2.6###68###28###96###58

Soybeans###48###10.8###250###123###373###180

Chickpeas###41###5.0###85###85###170###70

ISSUES OF INOCULATION:

Sowing inoculated seed into dry soil is not recommended where a legume crop is shown the first time. However, there is a low risk of inoculation where a legume has been used frequently and the soil is not hostile to rhizobia. Rhizobial inoculations applied in furrow sowing are placed deeper in the soil and will have a better chance of survival.

RECOMMENDATIONS AND PRECAUTIONS

- The inoculated seeds should be sown within six hours of inoculation.

- Never mix inoculants with fertilizers which are acidic.

- The following mixtures are NOT compatible with peat liquid and freeze dried inoculation.

a) Chemicals containing high levels of zinc, copper, sodium molybdate, manganese or mercury

) Fungicides and insecticides containing endosulfan or carbofuran.

METHODOLOGY OF INOCULANTS APPLICATION

Usually the inoculants are applied in two ways;

1-Seed Inoculation

This process needs the inoculants stickers which are usually in the form of Arabic gum or carboxyl methyl cellulose

2-Soil Inoculation

In this process the inoculation is done by two ways

- Dry application

- Wet application

In dry application the inoculants are added into the soil or sand with the ratio of 10 g/kg then mixed thoroughly by shaking. If you are applying inoculants with hand then it should be used at the rate of 1 kg/100 meter row. In the wet method the inoculants is mixed in water at the rate of 10 g/L, after mixing it is applied at the rate of 1 L/100 m row.

References

Ryder M and Denton M (2014) University of Adelaide and Ross Ballard - South Australian Research and Development Institute.

Unkovich MJ, Baldock J, Peoples MB (2010) Prospects and problems of simple linear models for estimating symbiotic N2 fixation by crop and pasture legumes. Plant and Soil 329, 75-89.
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Author:Aslam, Zubair; Zaman, Qamar uz
Publication:Technology Times
Geographic Code:9PAKI
Date:Dec 20, 2015
Words:932
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