**6. Role of legumes in improving soil quality**

Legumes have long been recognized and valued as "soil building" crops. Growing legumes improves soil quality through their beneficial effects on soil biological, chemical and physical conditions. When properly managed, legumes will:


These improvement factors depend on legume type, remaining plant residue left over in soil along with environmental conditions.

The legumes crops that are capable of fixing large amounts of nitrogen under good moisture conditions, can significantly improve the nitrogen supply for succeeding crops when grown annually. Annual grain legumes are normally grown for grain production along with green manure crops. The selection of legume type and variety mainly depends on minimum support price of the crop, including the climatic adaptability to that particular area (e.g., few varieties of chickpea and lentil are more drought-tolerant than faba bean and pea), adaphic factors, disease tolerance, etc. The effect of perennial forage legumes on soil quality is generally to greater extent and for longer duration than of annual pulse crops. The root structure and growth habit generally determines the amounts of nitrogen fixed by grain legumes and the shallow roots of pulses with short growth cycle become a limitation for their influence on soil physical conditions. However, during the growth of grain legumes, considerable amounts of nitrogen are leaked from roots into the soil. Also, the residues from these crops have a higher nitrogen content than cereal straw and they break down more readily, releasing nitrogen into the soil. Thus, cereal crops that follow grain legumes require less N fertilizer.

Biennial forage legumes e.g., sweet clover, yellow-flowered type is preferred by farmers. It is more drought-tolerant, shorter, and finer stemmed and leaved. These characteristics make it a more palatable livestock feed and easier to incorporate as green manure. Sweet clover is one of the most suitable crops for use as a green

**105**

*Sustainable Production of Pulses under Saline Lands in India*

manure. This helps in recovery of soil moisture reserves and residue decomposition during the partial fallow period. Sweet clover is very well suitable on moderately saline soils or soils that have poor structure due to very low levels of organic matter. An experiment on wheat with sweet clover green manure in rotation for 3 years at Indian thin black soils yielded significantly more than with crop rotations with fertilized crops or fellow lands [21, 22]. Although unfertilized green manure-wheat-

Perennial forage legumes also add humus and soil nutrients in addition to fixing nitrogen. Again, the selection of perennial legume depends mostly on the useful-

Alfalfa is a well-known legume tolerant to drought, moderate salinity, winter hardy along with high yields which is widely grown over diverse range of adaphic conditions. Neutral to slightly alkaline soils favor the production and persistence of alfalfa but acidic soils (pH less than 6.0) limit the production severely. The drought tolerance of alfalfa is due to deep root system and hence it grows best on welldrained soils. It cannot grow well on soils with poor drainage and hence is flooding

Red clover, a perennial legume, has growth cycle shorter than alfalfa and therefore included in short duration intercropping system. Since, it is well adapted to diverse soil types, it is grown mostly for seed and feed in the moist areas. Red clover is sensitive towards salinity or drought but tolerance level to acidic soils is more than

Forage legumes have deep root system and longer growth period thus have greater capacity for nitrogen fixation and hence improve soil quality more effectively. Biennial and perennial forage legumes add more nitrogen and organic matter in second year after under seeding in cereals in wet areas. Regular green manuring with forage legumes on degraded soils with typically low organic matter contents, adds more nitrogen and organic matter to the soil. It was found that yield of 12 successive wheat crops increased significantly than a non-legume system on a Gray soil in Northern Alberta. The reason may be addition of nutrients and nitrogen to soil from the deep-rooted legume improved soil quality. The benefit of using forage legumes as green manure enriched soil organic matter with nitrogen and readily decomposable plant residue. This also enhances the production of soil microbes and thus, fastens the nutrients availability. It was found [23] that deep-rooted perennial legumes take up phosphorus from the subsoil although available phosphorus is mostly found in the 0–6 inch depth and not below than 2-foot depth. Thus, green manuring with these legumes increases availability of

In an experiment at Saskatchewan, it was observed that tillage was easier with lower power requirements on soils following a perennial legume crop than after cereal grains. The reason may be improved soil structure with more porosity due to readily decomposable soil organic matter leftover by legumes. As a result, the water holding capacity of soil is increased and it becomes more friable and less erosive

Forage legumes also have the tendency to reduce salinity problems. Alfalfa uses excessive water through its deep roots and thus deep penetration of roots improves the internal soil drainage. A study at Outlook with irrigated alfalfa plowed-down in late fall or early spring indicated that the following cereal crop required little nitrogen fertilizer, while the second cereal required two-thirds of its usual amount

In view of above facts, key insights and findings from the literature and case studies across the three pillars of sustainability, environmental, social and economic

wheat rotation also yielded highest during the initial years of this study.

*DOI: http://dx.doi.org/10.5772/intechopen.91870*

ness of crop and soil type.

intolerant.

alfalfa.

soil nutrients.

and easier to till.

(Henry, University of Saskatchewan, Saskatoon).

impacts of pulses are summarized below.

#### *Sustainable Production of Pulses under Saline Lands in India DOI: http://dx.doi.org/10.5772/intechopen.91870*

*Legume Crops - Prospects, Production and Uses*

wheat up to 34%.

the entire cropping system.

in pulses is minimal in comparison to other crops.

**6. Role of legumes in improving soil quality**

• Increase soil aeration with reduced soil erosion

• Improve water-holding capacity of soil

over in soil along with environmental conditions.

that follow grain legumes require less N fertilizer.

from the air directly and fix at their own, hence, application of nitrogen as fertilizer

The nitrogen fixation property of pulses reduces the footprint of other crops in the soil adding to the food production cycle. In a study on durum wheat, it was found that carbon footprint was reduced by 17% in durum wheat when preceded by chickpeas or lentils, nitrogen-fixing crops, than preceded by a cereal crops. The impact of pulse-pulse intercropping with wheat system was much stronger than traditional cereal-cereal-durum rotation by reducing the carbon footprint of durum

The water requirement of pulses is also very less i.e., 1/2 to 1/10 of water in comparison to other protein rich crops [20]. Few pulses are well adapted to dry climates and hence can be produced better under dry/drought conditions, e.g., peas and lentils roots absorb less water from a lower depth. The water available in deep soil is, in this way, used by next crop, thereby increasing the water use efficiency of

Legumes have long been recognized and valued as "soil building" crops. Growing legumes improves soil quality through their beneficial effects on soil biological, chemical and physical conditions. When properly managed, legumes will:

These improvement factors depend on legume type, remaining plant residue left

The legumes crops that are capable of fixing large amounts of nitrogen under good moisture conditions, can significantly improve the nitrogen supply for succeeding crops when grown annually. Annual grain legumes are normally grown for grain production along with green manure crops. The selection of legume type and variety mainly depends on minimum support price of the crop, including the climatic adaptability to that particular area (e.g., few varieties of chickpea and lentil are more drought-tolerant than faba bean and pea), adaphic factors, disease tolerance, etc. The effect of perennial forage legumes on soil quality is generally to greater extent and for longer duration than of annual pulse crops. The root structure and growth habit generally determines the amounts of nitrogen fixed by grain legumes and the shallow roots of pulses with short growth cycle become a limitation for their influence on soil physical conditions. However, during the growth of grain legumes, considerable amounts of nitrogen are leaked from roots into the soil. Also, the residues from these crops have a higher nitrogen content than cereal straw and they break down more readily, releasing nitrogen into the soil. Thus, cereal crops

Biennial forage legumes e.g., sweet clover, yellow-flowered type is preferred by farmers. It is more drought-tolerant, shorter, and finer stemmed and leaved. These characteristics make it a more palatable livestock feed and easier to incorporate as green manure. Sweet clover is one of the most suitable crops for use as a green

• Enrich the soil N power with increased reserved organic matter

• Enhance soil biological activity with improved soil structure

**104**

manure. This helps in recovery of soil moisture reserves and residue decomposition during the partial fallow period. Sweet clover is very well suitable on moderately saline soils or soils that have poor structure due to very low levels of organic matter. An experiment on wheat with sweet clover green manure in rotation for 3 years at Indian thin black soils yielded significantly more than with crop rotations with fertilized crops or fellow lands [21, 22]. Although unfertilized green manure-wheatwheat rotation also yielded highest during the initial years of this study.

Perennial forage legumes also add humus and soil nutrients in addition to fixing nitrogen. Again, the selection of perennial legume depends mostly on the usefulness of crop and soil type.

Alfalfa is a well-known legume tolerant to drought, moderate salinity, winter hardy along with high yields which is widely grown over diverse range of adaphic conditions. Neutral to slightly alkaline soils favor the production and persistence of alfalfa but acidic soils (pH less than 6.0) limit the production severely. The drought tolerance of alfalfa is due to deep root system and hence it grows best on welldrained soils. It cannot grow well on soils with poor drainage and hence is flooding intolerant.

Red clover, a perennial legume, has growth cycle shorter than alfalfa and therefore included in short duration intercropping system. Since, it is well adapted to diverse soil types, it is grown mostly for seed and feed in the moist areas. Red clover is sensitive towards salinity or drought but tolerance level to acidic soils is more than alfalfa.

Forage legumes have deep root system and longer growth period thus have greater capacity for nitrogen fixation and hence improve soil quality more effectively. Biennial and perennial forage legumes add more nitrogen and organic matter in second year after under seeding in cereals in wet areas. Regular green manuring with forage legumes on degraded soils with typically low organic matter contents, adds more nitrogen and organic matter to the soil. It was found that yield of 12 successive wheat crops increased significantly than a non-legume system on a Gray soil in Northern Alberta. The reason may be addition of nutrients and nitrogen to soil from the deep-rooted legume improved soil quality. The benefit of using forage legumes as green manure enriched soil organic matter with nitrogen and readily decomposable plant residue. This also enhances the production of soil microbes and thus, fastens the nutrients availability. It was found [23] that deep-rooted perennial legumes take up phosphorus from the subsoil although available phosphorus is mostly found in the 0–6 inch depth and not below than 2-foot depth. Thus, green manuring with these legumes increases availability of soil nutrients.

In an experiment at Saskatchewan, it was observed that tillage was easier with lower power requirements on soils following a perennial legume crop than after cereal grains. The reason may be improved soil structure with more porosity due to readily decomposable soil organic matter leftover by legumes. As a result, the water holding capacity of soil is increased and it becomes more friable and less erosive and easier to till.

Forage legumes also have the tendency to reduce salinity problems. Alfalfa uses excessive water through its deep roots and thus deep penetration of roots improves the internal soil drainage. A study at Outlook with irrigated alfalfa plowed-down in late fall or early spring indicated that the following cereal crop required little nitrogen fertilizer, while the second cereal required two-thirds of its usual amount (Henry, University of Saskatchewan, Saskatoon).

In view of above facts, key insights and findings from the literature and case studies across the three pillars of sustainability, environmental, social and economic impacts of pulses are summarized below.
