The fertilizer was applied after thinning of Eucalyptus plantation 3 years old. Growth assessment was carried out a year later. At the same time diameter growth was evaluated, but showed no increase.The soils of the region have good availability of nitrogen, but are poor in phosphorus.
How did you measure diameter growth? A tape/caliper at DBH? As a first, I would have a look at the accuracy of your DBH measurement versus the expected annual growth for young Eucalyptus.
Are you sure the shoot growth, possibly a longer top shoot, is caused by the N application?
On the soils. Where is the base N (before fertilization) coming from in the 'region'? And on site?
Hi. I gladly answer the questions raised by you and expand on some methodological issues.
Design: complete random blocks
Repetitions: 3
Plots: 900 m2
Trees: 50 plot
DHB: diameter tape
Ht: Vertex
Soil Kandiudultes
Nitrogen Availability: High
P Availability: Low
Effective depth:> 2 m
Rainfall: 2000 mm annually
These are some of the characteristics of the test. Please all you want to know ask me.
Enriching the exchange and hope we can induce an issue that is affecting plantations fertilized.
regards
If N is limiting net primary productivity in your plantation, an application of N fertilizer would be expected to increase LAI leading to an increase in NPP (or mean annual increment) which should result in a measurable increase in biomass/volume of the dominant vegetation. Did you observe a significant increase in volume growth following application of the N fertilizer?
Hi Mason. Ok, that's right what you say. Equally we do not measure LAI and biomass measurements only did growth. In this measurement of growth we found that only the height of the planting responded significantly, but did not the diameter. In short, having more tree height no greater amount of biomass. The question that had never happened is that the only increase in yield and plant height did not happen in diameter. Regards!
Hi Rodolfo, first if the trees were taller with the same diameter then the volume increased. Secondly, is the uncertainty in the dbh data small enough relative to the annual increment for meaningful measurement? If not can that be improved?
Hello Paul. First, the diameter of the trees fertilized plots and the control plots was the same. In the same plots the height was greater in those that were fertilized. Second, if the difference was small compared to the annual increase. Personally, I think no longer will be better over time. Regards.
Mostly eucalyptus planting is done on waste lands without fertlizer application in India. But eucalyptus show good response to nitrogen for growth and phosphorus and sulphur for high essential oil content from leaves.
Hello Suresh. In our region forest plantations are made in high quality sites, so the surprise of the response! Usually in low nutritional quality sites the answer is positive and increasing growth is financially viable. But high quality sites the answer is not so clear from the financial point of view, but we encourage you fertilizer to replenish nutrients removed with forest harvesting. regards
In field crops the main function of N is to promote vegetative or shoot growth, the above-ground parts of plants, while root growth is mainly associated with P nutrition. I think it may be the same for trees. But following the principle of balanced fertilization is very important for healthy plant growth and maximum yield.
The N fertilizer response depends upon the initial N-Availability within the soil, other nutrients availability, moisture availability, crop / cultivar type, soil health mainly biological, prevailing weather conditions for deciding the net N mineralisation. When the experimental site has already higher soil N availability, physiological efficiency of applied N may be lower. Also since the height increase, definitely the biomass per unit area increase. These growth and its attributing characters need to be evaluated for working out the N-Fertilization response.
kind regards
naveen kalra
I agree with the excellent points given by Dr. Kalra. The initial soil physico-chemical and biological properties are very important for the response of plants to nutrients in the soil or applied as external input. In regards to N, determining the soil N and organic matter contents is very important because about 98% of N is found as organic form in the soil.
Agreed and thanks Dr Getachew for supplementing the answer, soil N balance is a complex process and there are crop simulation models DSSAT, INFOCROP (developed by our team at IARI), APSIM, which covers dynamically soil N balance components and the models are well calibrated and validated
regards
naveen kalra
Hello Getachew. Very interesting your answer. Maybe I could find the answer considering this comment. You should bibliography which can justify this? regards
Very interesting what you say Dr. Kalra. I want to know the simulation models. Could you give me those papers? regards
Crop response to any nutrient is always site specific , the magnitude of which will will vary as per nutrient sttaus in soil.Here is a case which justifies this statement ...
The final results are presented ( Herbert 2010) of a comprehensive N, P,K and dolomitic lime factorial experiment with Eucalyptus grandis planted on a fully cultivated Mispah soil series. On this marginal site, fertilising had a marked effect on the growth of E. grandis as measured at clearfelling at eight years and three months. The response to single fertiliser elements was greatest for potassium, followed by phosphorus and nitrogen, dolomitic lime having a depressive effect. The best N:P elemental fertiliser ratio was 3:1, while that for P:K was 1:3. Overall, an elemental N:P:K mixture of 3:1:3 was superior, increasing growth with rate of application. Fertilising with 100 g LAN (26% N), 100 g single superphosphate (8,3% P) and 50 g potassium chloride (50% K) increased yields at clearfelling from 56,7 t/ha for no fertiliser to 85.0 t/ha, an improvement of 49,8%. This fertiliser application is recommended for planting E. grandis on shallow soils derived from Ecca shale. Fertiliser treatments also affected form factor significantly, ranging from 0,370 to 0,411 and resulting in volume differences of 11.1% for trees with the same D.B.H. and height. Not only was the response to fertilising highly profitable in itself, but it also rendered the establishment of E. grandis to be viable on an otherwise uneconomically suitable site.( Source Herbert 2010, http://dx.doi.org/10.1080/00382167.1983.9628859)
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