Phosphorous is important for plant growth, especially for young plants. Without enough phosphorous, seeds won’t germinate and roots wont develop properly. Phosphate is needed for fruit to grow and ripen.
Put simply, a lack of phosphate will leave your plants stunted and will reduce fruit yields. You might also see a purple tinge to the leaves of plants that aren’t getting enough phosphate.
Unlike nitrogen, the air in our atmosphere doesn’t contain a lot of nitrogen. Phosphate for commercial fertilisers is made from phosphate rock that is mined from the ground.