The evaluation of a controlled release nitrogen fertiliser

Experiments in the laboratory, glasshouse and in the field assessed the chemical and agronomic characteristics of four polymer-coated urea products manufactured to different specifications, by altering the number and chemical nature of the coatings. (The chemical and physical nature of the coatings and the coating process are the property of the New Zealand distributor, Eko 360 Ltd.) They are claimed to be controlled release nitrogen (N) fertilisers. The N release characteristics of the experimental products were measured, relative to water soluble urea, in the laboratory in the absence of soil. These results confirmed that the N release rates were consistent with the distributor's specifications and were slower than urea. A glasshouse experiment was designed to use N uptake by ryegrass as a proxy for the N release rate in a soil. These results confirmed those from the laboratory, indicating that soil had little effect on the relative N release characteristics of the fertilisers. The experimental product with the slowest release rate was selected for evaluation in the field. In three field experiments the effect the experimental product, applied once at two rates, on pasture production was compared with the same rates of N applied once as urea, over 5-6 months. The experimental product tested increased N use efficiency (NUE, kg DM/kg N applied) by between 5-50% depending on the site and rate of N application. Thus it is concluded that the products are as claimed - contolled release N fertilisers, relative to urea - and that this characteristic is expressed under field conditions. Proof-of-concept was therefore established. Keywords: fertiliser, nitrogen, nitrogen use efficiency, pasture, SmartFertTM, urea</jats:p

A critique: "Potassium requirements of pasture on Pumice soil" by Morton et al.

Morton et al. (2014) presented the results from two rates of potassium (K) pasture trials conducted on Pumice soils which commenced in spring 2009 and ran for 3 years. They reached a number of conclusions with respect to the management of potassium requirements on such soils, based on the soil Quick Test K (QTK) samples (0-75 mm) collected in spring and suggested that the results from these two sites were unique. While noting that soil samples were collected in the autumn, they did not include these data in their anaylsis and discussion of the results. This communication discusses the implications of this omission. Keywords: potassium, pasture, pumice, soil tests</jats:p

Evaluating the Agronomic Effectiveness of Fertiliser Products

One of the problems which arises when analysing and interpreting results from field trials designed to test the efficacy of fertilisers and fertiliser-type products on pastures and crops is the conundrum of Type 1 and Type 2 statistical errors: is the product having literally no effect, or is the trial not "powerful" enough to detect small differences. This problem can be objectively and pragmatically solved, when sufficient trial data are available, by using cumulative frequency distribution functions. In this paper we explain what cumulative frequency distribution functions are and their usefulness for determining the agronomic effectiveness of products. This technique is then applied to field trial data testing the effectiveness of a number of fertiliser and fertiliser-type products used in agriculture today. It is concluded that this approach provides a more objective basis for determining the efficacy or otherwise of fertilisers. Keywords: fertilisers, agronomic effectiveness, testing, field trials, cumulative frequency distribution.</jats:p

Further field evaluation of the controlled release nitrogen fertiliser Smartfert®

Five field trials were conducted over 2 years in which the effects of single applications of different rates of a controlled release nitrogen (N) fertiliser, Smartfert, on pasture production and pasture N concentration were measured, relative to the same rates of SustaiN. The 2016 trials also compared multiple applications of SustaiN with a single application of Smartfert. Pasture responses to SustaiN relative to the control generally occurred within the first one to three harvests following application and then declined and became negative in the later harvests. The pasture responses to Smartfert developed more slowly and were greatest after the third harvest. In terms of total production significant (P</jats:p

An assessment of current fertiliser practices in New Zealand hill country

In the last decade major reviews on the phosphorus (P), potassium (K) and sulphur (S) nutrient requirements of clover-based pastures in New Zealand have been completed. This has resulted in adjustments to the P, K and S pasture production functions and some changes to the critical levels for soil tests, and modifications to our interpretation of some soil tests such as Organic S and Reserve K. Applying this new information to New Zealand's hill country pastoral soils, using case studies, suggests that there is considerable unrealized potential to increase productivity. Keywords: critical levels, economics, fertiliser, pasture, phosphorus, potassium, soil fertility, soil tests, sulphur</jats:p