Growth and yield of sugarcane as a function of phosphorus doses and forms of application

ABSTRACT This study aimed to evaluate sugarcane growth and its agricultural and industrial yield influenced by phosphorus (P) sources and forms of application. The experiment was carried out at the Paisa Sugar Mill, in Penedo-AL, Brazil, from February 2012 to February 2013. The adopted experimental design was a randomized block in a factorial arrangement, with four replicates. The treatments consisted of five doses of triple superphosphate applied in the planting furrow (0, 50, 100, 150 and 200 kg ha-1 of P2O5), and three doses of Bayóvar reactive phosphate rock (0, 100 and 200 kg ha-1 of P2O5) applied in the total area. Phosphorus applied in the planting furrow improved sugarcane quality through the reduction of fiber and increases in purity, corrected pol, total recoverable sugar, ton of pol per hectare (TPH) and ton of sugarcane per hectare (TSH). The Bayóvar reactive phosphate rock promoted increases in stem diameter at 120 days after planting (DAP), TPH and TSH. For the interaction triple superphosphate applied in the planting furrow x Bayóvar reactive phosphate rock applied in the total area, there were significant differences in the number of tillers at 30 DAP, stem diameter at 120 DAP and TSH.

RPR revisited (2): Long-term farmer experience helps define the role of RPR in grazed pastures

The commercial introduction of reactive phosphate rock (RPR) to the New Zealand market in 1987 was the subject of much dispute regarding its efficacy, and the differing interpretations of field trial results. Twenty-five years on, it was considered time to seek the views of farmers who are long-term users of RPR, across a wide range of geographic, soil type, fertility, climate and farming operations. The fact that the farmers interviewed have all been farming successfully with RPR for many years enables conditions suitable for RPR use to be identified more clearly compared to earlier advice. This progress is discussed in the context of utilising the proven reduced phosphorus (P) run-off with RPR to reduce P eutrophication in P-sensitive catchments. Key words: Reactive phosphate rock, RPR, superphosphate, SSP, long-term use, phosphorus runoff, eutrophication, water quality, recommendations

RPR revisited (1): Research, recommendations, promotion and use in New Zealand

Reactive phosphate rock (RPR) has been studied extensively in field trials and laboratory research in New Zealand since the 1930s. This paper looks at the different approaches to research over the decades, at what conclusions were drawn, at the recommendations made to farmers, and at the commercial promotion and sales of RPR. It is not an exhaustive literature review, but sufficiently comprehensive to demonstrate the large amount of research conducted, and to document the important issues that have arisen, particularly with respect to advice being given to farmers. RPR research has suffered from a series of mishaps which have hindered, in one way or another, the results being accurately interpreted and passed on clearly to farmers. There is a need for specific advice for farmers regarding managing or minimising any lag in production following a switch to RPR. New Zealand's grazed pastures, water quality and "clean and green" image internationally are closely interlinked. Given the proven significant reduction in P losses in run-off to waterways with RPR, the conditions in which RPR can be successfully used in New Zealand's pastoral agriculture have been reassessed. Key words: reactive phosphate rock, RPR, superphosphate, SSP, TSP, PAPR, long-term comparisons, plot trials, grazing trials, fertiliser recommendations, history

New fertiliser options for managing phosphorus for organic and low-input farming systems

Plant-available phosphorus (P) has been found to be limiting crop and pasture production in Australian dryland, broadacre, organic farming systems. The present review examines the mechanisms that act to provide organic sources of P to soil or mobilise P stored within the soil. A range of products is available to exploit one or more of these mechanisms to achieve a claimed improvement in P fertility. These products are described, and where possible, scientific research of their effectiveness is reviewed. The use of microbial inoculants, although successful in laboratory and glasshouse experiments, has returned varied results in field trials. The addition of organic fertilisers, such as composted or elemental sulfur (S) enriched reactive phosphate rock (RPR), tended to produce more reliable results. The variable nature of the composting process creates complexity in the production of composted RPR. The increased dissolution of RPR by the oxidation of added S has been successful in increasing available P content above that of RPR alone. This is especially significant to low-rainfall areas where RPR tend to be ineffective. This paper highlights the need for development and optimisation of the many organic fertilisers and additives available to organic producers. In all cases, products still require rigorous field and economic evaluation so that organic producers can be confident in making decisions that are informed, correct, and profitable with regard to P fertility. The alleviation of P deficiency is vital to the increased adoption and sustainability of boardacre organic farming in Australia.