Neem seeds are collected from June-August in rainy season.
There are normally 3500 to 5000 seeds per kilogram.
 
Azadirachtin content (%)  in Neem parts are:
 Neem oil 0.01-0.1
Seed Cake 0.005-1.2
Seed Kernels 0.35-0.89
Aqueous extract 0.001-0.02

Neem can be used throughout the entire crop production cycle.  
Products from Neem can be dipped, drenched, mixed with liquid fertilizers in drip systems and applied with all spray equipment including thermal fog and ultra low volume systems.

The oral LD – 50 of Azadirachtin is greater than 5000 mg / kg in rats.
Neem is thus less acutely toxic (according to LD – 50 in mg / kg in rats) than
Table salt (3750),
Aspirin (1200),
Caffeine (250),
Nicotine (50),
While Pyrethrum (900 – 1500) and
Rotenone (150 1500) are relatively safe and have been used over a period of time,

Neem products are among the safest of any and all orgainc pesticides.
 
Extensive toxicological studies have been carried out on Neem products in the USA and have been finally cleared for use in horticulture by the EPA.

Neem and Neem Extracts and other natural products like Equisetum, Reynoutria, Pyrethrum, Rotenone, Quassia, Ryania, Sabadilla are permitted to be used in organics in the USA and are classified as biorationals.

NEEM

Botanical Name : Azadirachta indica
Family : Meliaceae
Subfamily : Melioideae
Tribe : Melieae
Common Name : Nim, Neem, Limba, and Nimba etc.

In India, Neem occurs in tropical dry deciduous and thorn forests (Champion and Seth, 1968) and in the drier parts up to 1500m.

This amazing tree lives for over 200 years and can thrive well under
semi-arid and sub-humid conditions up to 700 meters above sea level.
It is tolerant to soil and even drought.
It is favored for afforestation of dry areas for checking soil erosion and as windbreak.

Neem is a moderate to large tree with a stout and rather short stem, generally branching early and forming a large, fairly dense and rounded crown of bright green foliage. Normally, it attains a height of 12-15m, rarely unto 25m, and a girth of 1.8-2.5m.

Neem grows on most types of soils. It can grow on compact clay or laterite crusts, however black cotton soils are preferred.
It comes up well in moderately saline and alkali soils with high levels of sodium carbonate and bicarbonates. It is a popular shade and avenue tree.

Neem has been extensively planted through the centuries all over the Indian countryside. It thrives better than most other species on dry, stony shallow soils where vegetation is scarce. Neem does best where drainage is good and the subsoil water level is fairly high, but it can persist even under very adverse soil conditions. If soil conditions are adverse, soil management and irrigation management can improve its establishment and growth. 

Neem is a light demander; it has a great capacity for pushing its way through thorny shrub in the seedling stage.
It is drought-hardy and can withstand drought better than excessive rainfall, as its root travel long distances in search of water from the sub-soil.
It can grow in temperatures from 0º C to 50ºC.
It can withstand rainfall of 450 to 1150 mm per year although neem grows on sites with as little as 250 mm rainfalls.
The tree in wind-firm, the branches are seldom broken even in storms.