Hello Karthik, since you are aspiring to do Agribusiness management, you have to first of all assess the benefits and opportunity cost of giving these entrance exams.
CAT 2019
It is a national level sought-after entrance examination conducted by the IIMs on a rotational basis. The official notification regarding the CAT exam 2019 will be released in month of July 2019(i.e, the last Saturday of July). Around 2 lakh aspirants apply for this exam every year. It's score is accepted by 20 IIMs and 100 B-schools across India. As you may know IIMs are the most coveted management institutes in our country, if you want you should apply for this exam.
CAT is an online computer based exam conducted for a duration of 180 minutes carrying 300 marks, and three timed sections- Verbal Ability and Reading Comprehension (VARC), Data Interpretation and Logical Reasoning (DI&LR), and Quantitative Ability (QA). There are 100 questions. Also, this examination has a negative marking scheme for each wrong answer. The application fee is 1900 for General category and 950 for SC/ST/PwD category.

XAT 2020
Xavier Aptitude test (XAT) will be conducted by XLRI Jamshedpur in the first week of January 2020. It is also a national level entrance test. It will help you get into 150 management institutes that accept XAT score. These are some of the top colleges in the list:
1.XLRI -  Xavier School of Management Jamshedpur
2.Department of Management studies, Indian institute of technology, Madras
3.SP Jain Institute of Management and Research,  Mumbai
4.TA Pai  Management Institute, Manipal
5.Great Lakes Institute of Management, Chennai
6.Xavier Institute of Management, Xavier University, Bhubaneswar.
Registration for XAT 2020 will start from the second week of August 2019. Total of around 75000 students apply for this examination across 46 cities. It will be a computer- based test as well, comprising of two parts- Part A consists of MCQ questions and Part B consists of general knowledge questions. It will be a 180 minutes test with four sections ( VA & LR, DM, QA & DI, and GK). The marking scheme consists of negative marking as well.
IIFT
The Indian Institute of Foreign Trade is deemed to be University with a public/ government ownership. It was established in 1983, and ranked 15 in MBA. It has got NAAC 'A' accreditation. A co-ed University approved by UGC, and a total faculty of 43 and 5 acres campus size. It is ranked 23rd by NIRF. The courses provided in management are:
1. MBA
2. MBA international business
3. MBA international business part time
The median packages of placements in MBA are  15.07 lakhs.  The fee structure varies from 7- 16 lakhs depending upon the course you choose.
It is an offline national level entrance exam, for admission to its MBA programs in Delhi, Kolkata and Kakinada campuses.
Its major recruiters are  Axis Bank, Amazon, Yes Bank, Citibank etc.
To get an in-depth knowledge of colleges provided Agribusiness management courses, and the entrance exams they accept visit this site: https://bschool.careers360.com/colleges/list-of-agriculture-business-management-colleges-in-india
All the best!
I hope this helps.