Depending upon the purpose, it can be done 2 to 6 times in a year for perennial trees.
Generally the leaf part is collected. In some cases, like grape and papaya, the petiole sample is collected.
Recently mature leaf called “Index Leaf” can be collected. The age of the leaf varies depending upon the crop.
Generally the leaf samples may be collected before fertilization during pre-monsoon and post-monsoon periods. Depending up the crop and purpose, the period can vary.
If the leaf samples are tested, one will know the fertilizer that has been applied has been taken by the plant or not. You can also know the hidden hunger of the plant for correcting and to get good production.
If soil is analyzed for various nutrients, one will know the capacity of the soil to supply nutrients for the crop that is being grown.
Before fertilization or after 4 to 5 months of fertilizer application, the soil may be collected.
The soil should be dried in shade but not in sunlight.
Soil Augars, Spades, Crowbar etc.,
From a uniform field of 1 acre, 10-15 sub-samples can be collected in a zig-zag manner and can be made into a sample of 1 kg by quartering method.
In general, the soil samples can be collected from 0” – 9” depth or 0” – 12” depth for nutrient analysis purpose depending upon the corp.
The soil samples should be collected from the field by moving in a zig-zag manner.
Phosphorous is a relatively immobile fertilizer nutrient and suffers from instantaneous fixation if intimately mixed in the soil. Normally, the crop absorbs most of its P requirement during early vegetative stage and therefore one basal application is adequate. Keeping these points in view, banding of superphsophate 5cm below the seed/plant row led to the maximum utilization of the fertilizer in most crops except okra which performed when placed 10cm below the seed row. As a result in brinjal, a saving of 40% of P input and in tomato and onion, a saving of 20% was achieved without loss in yield. In other corps, any reduction in p-input reduced the yield.
The N use efficiency can be maximized by increasing the number of split applications. However, it is not advisable to exceed 3 split applications as the increased cost of fertilizer application makes it cost-prohibitive.
Among 6 popular cropping sequences practiced around Bangalore, the most efficient sequences were French bean-tomato-onion (38.37% utilization of N applied to first crop) and Okra-cabbage-brinjal (21.82%). Different combinations of crops in the same sequence also differed significantly. For instance, the sequence of Tomato-onion-French bean was the best (42.13%) in the former sequence while Cabbage-okra-brinjal (23%) was superior in the latter sequence.