On a proposal I evaluated, a student planned to examine the effects of 3 levels of intra-row Spacing and 4 NPS Rates on Growth and Yield of Garlic. The student designed the treatment structure for NPS rates as follows:
NPS rate (kg ha-1)
10, 29 and 5
19, 38, and 7
28, 47 and 9
38, 57 and 11
As I think the student may use the proportions of N, P and S in NPS fertilizer blend, i.e., 19%, 38% and 7% as a basis to set his treatment structure. I claimed that this treatment structure is wrong and suggest changing it into 0, 50, 100 and 150 kg ha-1 NPS rate, or something like that. But, the student and his supervisor refuse my suggestion.
Dear Professors and colleagues, is it really the correct way of treatment structure? If not, what is your advice for them?
after having a thorough review of some answers i have decided to add the following remark on my earlier question
Remark: The student is not making a physical blend of each fertilizers rather he will use the already blended form of NPS fertilizer.
You are right, it is always a preferred choice to have equal difference between treatments in order to find out most profitable fertilizer rate..
I propose: N as 10, 20 , 30 and 40 kg/ ha; P as 15, 30 , 45 and 60 kg/ ha ; S as 3, 6 , 9 and 12 kg/ ha in a factorial randomized experiment having total of 12 treatment combinations.
Dr. Srivastava answered rightly. @Tsegaye Babege, you can suggest accordingly.
Regards.
There is nothing wrong with the levels of their fertilizer treatments. What do you think is wrong about them? There's no reason why they should be pretty numbers like 50 and 100. It may make more sense for the purpose of the study to have a realistic fertilizer rates (10 - 38 kg-N/ha) rather than a wide unrealistic range (0 - 150 kg-N/ha).
I would suggest a non fertilized control.
Nitrogen at 0 10 20 and 40 kg/ha
P at 0 5 10 and 20 kg/ha
S at 0 2 4 and 8 kg/ha.
5 1 0.,4 ratio in a mixture
What would you like to examine: the best ratio between N, P and S or the total amount of fertilizers to be applied.
Finding out the best ratio will be difficult because you need to have for instance 3 different levels of N, 3 different levels of P and 3 different levels of S. So in total 3x3x3=27 treatments.
Of course with the 4 suggested treatments one might be giving the best results but maybe because this one has the best nitrogen level and the impact is maybe better then a S level that is not on a optimum level.
If you would only test 0, 50, 100 and 150 kg NPS then you are not really testing the ratio between the elements but just looking for the optimum for one blend.
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