Master of Science / Department of Agronomy / David B. Mengel / The increasing price of phosphorus (P) fertilizers has created interest among producers in ways to enhance the efficiency of applied P fertilizers. Research has long focused on increasing phosphorus efficiency through the use of fertilizer placement techniques (banding, strip applications, and in furrow placement with the seed). Recently, various products have been introduced and marketed claiming to increase efficiency of applied P or increase availability of native soil P. The objective of this study was to test the use of two such widely advertised products: Avail®, a long chain, organic polymer created to reduce the fixation of fertilizer P by aluminum and calcium, and JumpStart®, a seed inoculant containing a fungus (Penicillium bailii), which is said to increase the availability of fertilizer and native soil P to plant roots through the colonization of the root system and producing organic acid exudates. This study was conducted at multiple locations across Kansas with corn (Zea mays L.) in 2008 and 2009 and winter wheat (Triticum aestivum L.) in 2009. Selected sites varied in soil test P, with a majority of the locations having a Mehlich III P test of < 20mg kg-1, where a P response would be expected. Treatments consisting of P rates from 0 to 20 kg P ha-1 with and without the addition of Avail were applied at planting. At many locations, each of the fertilizer/Avail treatments were planted with and without Jumpstart seed treatment. Plant samples were collected at early and mid-season growth stages. Harvest data consisting of grain yield, grain moisture content at harvest, test weight or bushel weight and grain P content also were collected to measure treatment response. Plant samples for both trials failed to show consistent responses to the addition of either product. Excellent corn grain yields were obtained at seven of eight site years with location averages above 12,500 kg ha-1. One location displayed a significant grain yield response to P in both 2008 and 2009. There were no significant responses to enhancement products where a response to P was seen. At two of the five wheat trials, a significant tissue P response to the addition of P was seen. At one location with very low soil test, 6 mg kg-1, P fertilization increased rate of maturity. No effect on growth or yield at either P responsive or unresponsive sites was seen in wheat due to the use of enhancement products. A series of 20 single replications sites were conducted with the JumpStart product in cooperation with County Extension Agents as a part of wheat variety demonstrations. Analysis of this data showed a significant decrease in wheat yield with the addition of JumpStart in 2009. Overall, this study showed a lower than expected frequency of response to applications of P fertilizer based on soil test and the KSU P fertilizer recommendations. It also showed no response across locations, years and crops to the use of P fertilizer enhancement products.

Soluble phosphorus fertilizer is bound in the soil rapidly after application in soils high in calcium. A fertilizer additive known as AVAIL® (J.R. Simplot Company) is purported to keep applied phosphorus fertilizer more available to plants by binding to soil minerals such as calcium, magnesium, and iron, thereby reducing phosphorus binding. This could prove useful due to the attraction of AVAIL® with cations such as Ca2+, but is fairly unstudied for dryland wheat production on alkaline, calcium-rich soils. The objective of this study is to evaluate the effect of low-rate fertilizer treatments with AVAIL® on dryland small grain yield on calcium-rich, eroded hillslopes in a fallow-wheat crop rotation. Two experiments were conducted to determine treatment effects on yield and grain quality for (1) above-ground dispersed (broadcast) application of monoammonium phosphate (MAP; 52% P2O5 content) fertilizer in the spring (2017), and (2) fall application of MAP incorporated with the seed (banded) at planting (2018). Fertilizer treatments were the recommended rate (60 lbs/ac) or one-half the recommended rate (30 lbs/ac) for dryland small grain, with or without AVAIL® (four treatments), replicated four times in a strip-block design for the 2017 experiment and replicated 3 times in a randomized complete block design for the 2018 experiment. Experimental blocks were assigned to hillslope erosional severity groups. The erosional severity groups were v designated (non-eroded, slightly eroded, highly eroded, and depositional slope segments). Hillslope segmentation allowed for correlations between calcium carbonate, organic matter, and yield levels across treatments. Results from the broadcast study indicate that there was no yield advantage of any treatment at any level of erosional severity, saving a grower $20.30/acre by applying 30 lbs/acre of MAP. However, 30 lbs/acre of MAP with AVAIL® showed similar yield to 60 lbs/acre of MAP without AVAIL®, potentially saving a grower $6.42/acre over standard growing practices. The incorporated study also indicated that there was no reliable yield advantage of any fertilizer treatment at any level of erosional severity, saving a grower $15.37/acre by applying 30 lbs/acre of MAP. Neither treatment with AVAIL had greater yield or profit than those without AVAIL. Profit for the 60 lbs/acre of MAP treatment narrowly outperformed 30 lbs/acre of MAP by $1.73/acre, indicating that growers may be able to reduce phosphorus use under dryland growing conditions with optimal fertilizer placement.

Phosphorus (P) is poorly soluble in most soils and, thus, has poor plant uptake efficiency. AVAIL® and Carbond P (CBP) are new fertilizer products shown to increase P use efficiency (PUE) and increase crop yields when grown in P limiting soils. Carbond P has specifically been seen to increases P uptake and crop yields in soils low in P, although effectiveness in regards to soil organic matter is unknown. The objectives of these studies were to determine if the mode of action for these products is related to physiological response, to determine if Carbond P is toxic to plant roots when in direct contact at high rates, and determine the limitations of Carbond P in regards to biomass (yield), P uptake and concentration. We used a hydroponic study to compare CBP to AVAIL in evaluating plant toxicity and plant philological response. AVAIL and CBP were also compared to ammonium polyphosphate (APP) at pH 6 or 8 for hydroponically grown maize (Zea mays L.). Additionally, a glasshouse study evaluated the PUE of CBP with soil in which maize was grown. Soils were moderate or high in organic matter, with 0, 5, 15, 45, or 135 kg P2O5 ha-1 applied as either APP or CBP. Both studies showed that CBP is a suitable PUE enhancing fertilizer. In the greenhouse study, the high organic matter soil revealed that both CBP and APP fertilization resulted in similar increases in biomass yield and P concentration and uptake. However, in the moderate organic matter soil, biomass and total P uptake was significantly greater for CBP than APP at the two lowest P rates of fertilization and significantly higher for APP than CBP at the highest P application rate. In the hydroponic study, neither AVAIL nor CBP had any positive or adverse effects on the plants as compared to APP. These results, coupled with this and previous soil-based greenhouse and field studies with AVAIL and CBP, show that the increase in PUE is not a physiological growth stimulant response, but rather likely the result of impacts on P solubility in the soil. However, the presence of high organic matter in the soil seemed to negate the effects of the organic acid bonded P used in Carbond P. We conclude that CBP, and possibly other organic acid based fertilizers, can assist in furthering agricultural goals, as well as environmental responsibility with these known limits.