Legume, sorghum and cotton effect

Legume effect

The legume or fabaceae crops are known for their nitrogen fertilizer fixing ability in field. Continuous growing of a non-legume crop may cause the problem of nutrient exhaustion. The nutrient exhaustion results in poor soil and unhealthy plant growth. Inclusion of fabaceae crops in crop rotation programme helps in overcoming this problem. Hence, legume effect is the beneficial effect of the legume crops in different crop rotation and cropping system.

What are the benefits of the inclusion of legumes in a cropping system?

Nitrogen fixation: Crops fix atmospheric nitrogen in root nodules. This results in the improvement of the nitrogen status of soil.

Intercropping: It saves up to 25% recommended level of nitrogen application. The other crop content in intercropping is cereal crop.

Effect of crop residues: Root nodules and crop residues release nitrogen during decomposition. It will benefit succeeding crop.

Absorption of phosphorus: These crops absorb soil phosphorus very efficiently. We all know that phosphorus is immobile in soil.
But in plant, it is an mobilized organic matter. The succeeding crop will receive it through previous crop residues. These crops convert inorganic phosphorus into organic phosphorus.

CEC: These crops have better root CEC or cation exchange capacity than cereals. They absorb more of divalent cations, such as Ca2+ and Mg2+. With low CEC, they do not compete for monovalent cation, such as K+ with the cereal plants.

Sorghum effect

Fast growing cereal crops: Fast growing cereal crops exhaust the nutrient status of soil very fast.

C:N ratio: The C:N ratio of these crops is high.

Decomposition of the crop residues: The decomposition of these crop residues take a very long time.

Immobilisation of nitrogen: During the process of decomposition, part of soil nitrogen is temporarily immobilised.

When sorghum is the main crop: This severe becomes more problematic in sorghum field. And to reduce sorghum effect, 25% more N is given at the time of fertilization. It enhances the process of decomposition and overcomes the immobilisation of nitrogen.

Cotton effect

Cotton prefers the deeper layers of the soil. It removes comparatively smaller quantities of nutrients. The succeeding crop with shallow root system are able to use the nutrients of surface layers of the soil. This is cotton effect.

Multiple choice objective questions

Also read: Agronomy mcq and answer

Question 01. Which crop will produce legume effect?

(a). Wheat.
(b). Rice.
(c). Maize.
(d). Black gram.

Question 02. Which is a nutrient exhaustive crop?

(a). Red gram.
(b). Pea.
(c). Paddy.
(d). All of the above.

Question 03. How do a plant fixes nitrogen into soil?

(a). By using applied nitrogen.
(b). From atmosphere.
(c). From ground water.
(d). All of the above.

Question 04. Which is immobile in soil?

(a). Nitrogen.
(b). Phosphorus.
(c). Potash.
(d). None of the above.

Question 05. Which will be the best intercropping system in a paddy field?

(a). Rice – potato.
(b). Rice – lathyrus.
(c). Rice – maize.
(d). Rice – tomato.

Question 06. What is legume effect?

(a). Beneficial role of fabaceae crops in cereal crop cropping system.
(b). Beneficial role of fabaceae crops in fabaceae crop cropping system.
(c). Both a and b.
(d). None of the above.

Question 07. What is sorghum effect?

(a). Unavailability of nitrogen due to immobilisation.
(b). Unavailability of phosphorus due to immobilisation.
(c). Unavailability of potash due to immobilisation.
(d). None of the above.

Question 08. What is cotton effect?

(a). Uptake of upper nutrients by cotton plants.
(b). Uptake of of deeper nutrients by succeeding plants.
(c). Uptake of deeper nutrients by cotton plants.
(d). Uptake of upper nutrients by succeeding crops.

Question 09. How much nitrogen is necessary to reduce sorghum effect?

(a). 50%.
(b). 30%.
(c). 20%.
(d). 25%.

Question 10. What is allelopathy?

(a). Beneficial effect of one plant on another plant.
(b). Harmful chemical effect of one plant on anther plant, such as growth inhibition.
(c). Either a or b.
(d). None of the above.

Answer key

1.	d	6.	a
2.	c	7.	a
3.	b	8.	c
4.	b	9.	d
5.	b	10.	b