Introduction

The perception that cashew is a wild tree and useful for arresting soil erosion grossly underplayed its commercial importance as a highly priced confectionary nut! Because of this misconception crop management practices for cashew were never looked at seriously. Once it is realized that cashew nut has a very valuable role in trade things have changed. However, focus into Agronomy of cashew trees received very little attention. It is a tree that will grow to 10-12 years and would yield a few kilograms of nut! The very concept of value of space and time are changing in every sphere of human activity; and more readily in crop cultivation. So we do not intend to waste space (land surface) and time (time to yield or gestation period). So at Jain Irrigation, we started questioning the traditional agronomy and are consistently coming up with alternate and more revolutionary agronomy for crop after crop. After our huge successes with Mango, Banana and Guava we chose cashew for technology up-gradation. The result is ultra high density cashew plantation.

We planted Ullal 3 and VRI 3, two varieties representing two different types of Agro ecology. These were planted at 3 x 2 m and 4 x 3 m( row and Plant to Plant ) spacing; taking 674 and 337 trees per acre respectively.

The grafts planted were trained to get a single stem for 45-50 cm from the ground and then primary branches were initiated by heading back main stem at 45-50 cm height. At 6-8 month after planting selective thinning and heading back of primary branches to initiate secondary branches while at 8-10 month after planting heading back of secondary braches 35-40 cm was done to initiate tertiary branches. Pruning is done after harvest to initiate more numbers of shoots in small unit area and to remove criss-cross branches to ensure good sunlight throughout the canopy.

SPACING	3m x 2m		4m x 3m		5m x 4m
	Total	Girth	Total	Girth	Total	Girth
	Shoots	(cm)	Shoots	(cm)	Shoots	(cm)
Variety VRI 3	154.7	22.2	129.5	19.5	64.9	17.1
Variety Ullal 3	102.5	20.7	93.3	19.8	59.7	15.9

Input management

The UHDP plantation requires intensive input management in tune with the canopy management and flowering and fruiting.
The trees are drip irrigated and fertigated.

Drip irrigation and irrigation scheduling

Success of drip irrigation depends on both hardware (the physical system) and software (scientifically determined watering plan). The trees were given the exact water volumes required at each time.

Online drip system with 2 drippers of 4 lph or 8 lph placed at 45 cm away from the tree trunk are designed for drip irrigation.

Layout of drip lines in UHDP cashew
Table 2. Irrigation schedule for (3 x 2 m) Cashew plantation- Udumalpet Taluk, Tirupur dist.,

		Water Requirement L/plant/day
Month	Evaporation	1st yr	2nd yr	3rd yr	4th yr
	mm				Onwards
Jan	4.6	0.63	2.53	5.69	10.12
Feb	5.9	0.8	3.21	7.21	12.82
March	7.29	1	4	8.99	15.98
April	6.69	0.89	3.55	7.99	14.21
May	7.54	0.94	3.76	8.45	15.03
June	7.45	1.01	4.05	9.12	16.21
July	7.47	1.03	4.11	9.24	16.43
Aug	7.84	1.09	4.35	9.78	17.39
Sept	7.78	0.96	3.84	8.64	15.35
Oct	4.74	0.55	2.21	4.97	8.83
Nov	3.84	0.59	2.35	5.28	9.39
Dec	3.9	0.58	2.33	5.25	9.33
Avg	6.02	0.93	3.73	8.39	14.92

Fertigation

This is the most critical technology that results in highly tangible crop yield enhancements in the recent years. Fertilizers were originally applied to soil and crop plants are expected to take up what they wanted! Now things have changed. Nutrient elements (or radicles) in water soluble form is injected to the rhizo-sphere at a rate and time matching the crop need. This change results in high efficiency of fertilizer use and reduces wastage and fertilizer related pollution.

A major requirement for efficient fertigation is the knowledge that when, what mineral and how much of it that a crop requires. Research information in this line of science is very limited, especaillly crops grown in tropics. For this reason at Jain Irrigation we support basic research and support university research students to conduct research in our farm.

(JISL and TNAU, Coimbatore Collaborative Research Programme)

Effect of fertigation on yield

Inference

Cashew varieties responded to ultra high density and yielded very early (2nd year). The crop also responded to fertigation resulting in 4 times yield compared to that in conventional soil applied fertilizer. The results also showed that the recommended dose of fertilizer can be still reduced by 25% and harvest still higher yield. Based on the two year study it can be concluded that for VRI 3 and ULLAL 3 varities 3 x 2 m UHDP spacing is successful and fertigation at 75% RDF is most economical.

Benefits of UHDP cashew to farmer

Very low gestation period.
Early realization of income.
Suitable for small, medium and semi-large farmers as its management is intensive and yields good quality fruits which can get better market price.
It makes sensible bankable project to get financial support due to assured high early returns.