Phosphorus management on extensive organic and low-input farms

2009 ◽  
Vol 60 (2) ◽  
pp. 105 ◽  
Author(s):  
P. S. Cornish

A synthesis of the Australian literature reporting soil and plant phosphorus (P) status under organic methods of broadacre farming provides clear evidence that available soil P is lower in organic systems, although there have been no reports of farm P balances that might help to explain the lower P concentrations. There is also evidence, which is largely circumstantial, to suggest that P deficiency significantly reduces productivity of broadacre organic farms, but few experiments prove this conclusively because of other confounding factors. An overview of international literature suggests similar findings for mixed farms. Nine case studies further examined the constraints imposed by P on broadacre organic and low-input farms in Australia. Two farms on fertile soils had negative P balances but maintained productivity without fertilisers by ‘mining available’ P reserves. Five extensive organic farms on inherently less fertile soils had positive P balances because P fertiliser was used. Four of these farmers reported low productivity, which was supported by comparisons of wheat yields with estimated water-limited potential yields. Low productivity appeared to be related to P deficiency despite the use of allowable mineral fertilisers, mostly reactive phosphate rock (RPR), on these farms. The apparent ineffectiveness of RPR is most likely due to the modest rainfall at these farms (380–580 mm/year). The highest research priority is to develop effective, allowable fertilisers. Until this has been achieved, or ways of using less labile P have been developed, there is a case for derogation in the Certification Standards to allow the use of soluble forms of P fertiliser on soils with low soil solution P and high soil P-sorption. Two low-input farms practicing pasture-cropping had approximately balanced P budgets and from this perspective were the most sustainable of the farms studied.

2009 ◽  
Vol 60 (2) ◽  
pp. 163 ◽  
Author(s):  
A. M. McNeill ◽  
C. M. Penfold

Maintenance of available phosphorus (P) is a problem faced by both conventional and organic systems but it is exacerbated in the latter given that manufactured inorganic sources of P fertiliser are not permitted under the International Federation of Organic Agriculture Movements certification guidelines. The focus of this paper is a discussion of potential agronomic strategies to assist in sustainable management of the soil P resource in organic and low-input broadacre farming systems within the Australian rain-fed cereal–livestock belt. The paper considers three broad strategies for agronomic management of P in this context and draws on reported research from overseas and within Australia. An analysis of the current knowledge suggests that the option most likely to ensure that soluble P is not a limitation in the system is the importation of allowable inputs that contain P from off-farm, although for much of the Australian cereal–livestock belt the immediate issue may be access to economically viable sources. Research targeted at quantifying the economic and biological benefits to the whole-farm system associated with the adoption of these practices is required. Improving the P-use efficiency of the system by incorporating species into rotation or intercropping systems that are able to use P from less soluble sources has been a successful strategy in parts of the world with climate similar to much of the Australian cereal–sheep belt, and deserves further research effort in Australia. Agronomic management to maximise quantity and quality of pasture and crop plant residues undoubtedly builds labile soil organic matter and facilitates P cycling, but the strategy may be of limited benefit in low-rainfall areas that do not have the capacity to produce large biomass inputs. Evidence that organic or low-input systems naturally increase the numbers and diversity of soil organisms is sparse and published studies from Australian systems suggest that P nutrition is not enhanced. However, seed and soil microbial inoculants to facilitate improved P uptake have been developed and are currently being field tested in Australia. Progress in selection and breeding for cereal genotypes that are more P efficient and other plant genotypes that can use less labile P sources, is gaining momentum but still remains a long-term prospect, and may involve genetic modification which will not be acceptable for organic systems.


Biology ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 158
Author(s):  
Jiang Tian ◽  
Fei Ge ◽  
Dayi Zhang ◽  
Songqiang Deng ◽  
Xingwang Liu

Phosphorus (P) is a vital element in biological molecules, and one of the main limiting elements for biomass production as plant-available P represents only a small fraction of total soil P. Increasing global food demand and modern agricultural consumption of P fertilizers could lead to excessive inputs of inorganic P in intensively managed croplands, consequently rising P losses and ongoing eutrophication of surface waters. Despite phosphate solubilizing microorganisms (PSMs) are widely accepted as eco-friendly P fertilizers for increasing agricultural productivity, a comprehensive and deeper understanding of the role of PSMs in P geochemical processes for managing P deficiency has received inadequate attention. In this review, we summarize the basic P forms and their geochemical and biological cycles in soil systems, how PSMs mediate soil P biogeochemical cycles, and the metabolic and enzymatic mechanisms behind these processes. We also highlight the important roles of PSMs in the biogeochemical P cycle and provide perspectives on several environmental issues to prioritize in future PSM applications.


Agronomy ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 212 ◽  
Author(s):  
Thabiti Soudjay Kamal ◽  
Yunfeng Huang ◽  
Chulong Huang ◽  
Su Xu ◽  
Gao Bing ◽  
...  

We present a quantitative analysis of phosphorus (P) flows that characterize the food production-consumption system metabolism in a low-income, food, and phosphorus deficient country, using Comoros, a small African island state, as an example from the year 2000 to 2011. The data were interpreted in terms of the connections between crop production, livestock breeding, human consumption, and soil stock, using the substance flow analysis (SFA) model. We found that the total P input into Comoros totaled 132.37 t in 2000 and 270.60 t in 2011, whereas the total P output totaled 567.40 t in 2000 and 702.29 t in 2011. Farmers in Comoros are cropping with little or no P input, resulting in a soil P deficiency; it varied from 435.03 t in 2000 to 431.69 t in 2011. In addition, the Phosphorus Use Efficiencies (PUEs) of plant and animal production in Comoros were 131.80% and 14%, respectively, in 2011. This is the first SFA of a small island state, and the lack of a closed P loop is a major issue for the country in terms of P security and this has not changed between 2000 and 2011. This study proposes crucial solutions for improving the PUE through recycling and reusing animal manure, human excreta, and household solid organic waste.


1986 ◽  
Vol 66 (2) ◽  
pp. 303-313 ◽  
Author(s):  
J. F. DORMAAR ◽  
T. G. SOMMERFELDT

A long-term field experiment was initiated in 1973 to determine the safe loading capacity of a Lethbridge loam (Dark Brown Chernozemic) with feedlot manure. The effect of 10 yr of feedlot manure loading was examined by analyzing a number of inorganic and organic matter constituents of the Ap horizon. Although soil C, P, and enzyme activities increased as feedlot manure additions to the soil increased, these increases diminished at triple the recommended loading regimes. Phosphatase activity was checked by increased labile phosphorus levels. Levels of adenosine 5′-triphosphate increased but fluctuated with time under various moisture regimes. The C:N ratios, percent monosaccharide C of total soil C, and the ratio of deoxyhexoses to pentoses remained constant while the percentage of manure C retained decreased as feedlot manure loading increased. The distribution between pentoses and hexoses was strongly affected by feedlot manure levels while the deoxyhexose percentage of the sum of the eight monosaccharides determined remained about the same. Feedlot manure additions, at triple the recommended level, increased the labile P as a percentage of total soil P to around 50%. Although mineralization did not keep pace with the quantities applied, the presence of undecomposed manure did not seem to have harmful agronomic effects. Key words: ATP, feedlot manure, labile phosphorus, monosaccharides, organic matter


2007 ◽  
Vol 47 (8) ◽  
pp. 984 ◽  
Author(s):  
R. F. Brennan ◽  
M. D. A. Bolland

The effect of fertiliser phosphorus (P) and nitrogen (N) on seed (grain) yield and concentration of oil and protein in grain of canola (oil-seed rape; Brassica napus L.) was measured in two field experiments undertaken at eight sites from 1993–2005 in south-western Australia, on soils deficient in P and N. Six rates of P (0–40 kg P/ha as single superphosphate) and four rates of N (0–138 kg N/ha as urea) were applied. Significant grain yield increases (responses) to applied P occurred in both experiments and these responses increased as rates of applied N increased. For grain production, the P × N interaction was significant in all eight years and locations of the two experiments. Application of P had no effect on concentration of oil and protein in grain. Application of N always decreased the concentration of oil and increased the concentration of protein in grain. For canola grain production in the region, responses to applied N always occur whereas responses to applied P are rare, but if soil P testing indicates likely P deficiency, both P and N fertiliser need to be applied.


Author(s):  
John M. Wallace ◽  
Sarah Isbell ◽  
Ron Hoover ◽  
Mary Barbercheck ◽  
Jason Kaye ◽  
...  

Abstract Organic grain producers are interested in interseeding cover crops into corn (Zea mays L.) in regions that have a narrow growing season window for post-harvest establishment of cover crops. A field experiment was replicated across 2 years on three commercial organic farms in Pennsylvania to compare the effects of drill- and broadcast-interseeding to standard grower practices, which included post-harvest seeding cereal rye (Secale cereale L.) at the more southern location and winter fallow at the more northern locations. Drill- and broadcast-interseeding treatments occurred just after last cultivation and used a cover crop mixture of annual ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] + orchardgrass (Dactylis glomerata L.) + forage radish (Raphanus sativus L. ssp. longipinnatus). Higher mean fall cover crop biomass and forage radish abundance (% of total) was observed in drill-interseeding treatments compared with broadcast-interseeding. However, corn grain yield and weed suppression and N retention in late-fall and spring were similar among interseeding treatments, which suggests that broadcast-interseeding at last cultivation has the potential to produce similar production and conservation benefits at lower labor and equipment costs in organic systems. Post-harvest seeding cereal rye resulted in greater spring biomass production and N retention compared with interseeded cover crops at the southern location, whereas variable interseeding establishment success and dominance of winter-killed forage radish produced conditions that increased the likelihood of N loss at more northern locations. Additional research is needed to contrast conservation benefits and management tradeoffs between interseeding and post-harvest establishment methods.


Agronomy ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 784 ◽  
Author(s):  
Waqas Ahmed ◽  
Kailou Liu ◽  
Muhammad Qaswar ◽  
Jing Huang ◽  
Qinghai Huang ◽  
...  

Elevated mineral fertilization may change the composition and increase the availability of soil phosphorus (P) in subtropical paddy soils and thus affect long-term plant growth. However, an understanding of the response of soil P fractions to long-term nitrogen, phosphorus and potassium (NPK) additions remains elusive. This study aimed to explore the responses of soil P-fractions and their mobility to different long-term chemical fertilization rates under a double rice cropping system. The rates of nitrogen (N), phosphorus (P), and potassium (K) in the low NPK treatment (LNPK) were 90, 45, and 75 kg ha−1 year−1, respectively, and in the high NPK treatment (HNPK), they were 180, 90, and 150 kg ha−1 year−1, respectively. The results showed that the concentrations of soil organic matter (SOM), total P, Olsen P, total N, and mineral N were remarkably increased under HNPK by 17.46%, 162.66%, 721.16%, 104.42%, and 414.46%, respectively, compared with those under control (CT). Compared to the CT P fractions, HNPK increased the labile P fractions (i.e., NaHCO3-Pi and NaHCO3-Po) by 322.25% and 83.53% and the moderately labile P fractions (i.e., NaOH-Pi, NaOH-Po and HCl. dil. Pi) by 163.54%, 183.78%, and 3167.25% respectively, while the non-labile P was decreased by the HNPK addition. P uptake and grain yield were increased by LNPK and HNPK by 10.02% and 35.20%, respectively, compared with CT. P use efficiency indices were also higher under HNPK than under LNPK. There was a strong positive relationship between grain yield and P use efficiency (R2 = 0.97). A redundancy analysis (RDA) showed a strong correlation between soil chemical properties and the labile and moderately labile P pools. Structural equation modeling (SEM) revealed that SOM, mineral N, and available P strongly control the labile P pool. In conclusion, NPK additions under the paddy soils significantly influences the soil P fractions. The soil P dynamics and the mechanisms governing the interactions between plants and soil nutrients are clearly explained in this study.


2011 ◽  
Vol 57 (No. 5) ◽  
pp. 228-234 ◽  
Author(s):  
G. Xu ◽  
J.N. Sun ◽  
R.F. Xu ◽  
Y.C. Lv ◽  
H.B. Shao ◽  
...  

Little is known about the effects of air-drying and freezing on the transformation of phosphorus (P) fractions in soils. It is important that the way in which soils respond to such perturbations is better understood as there are implications for both P availability and loss to surface waters from soils. In this study, the effects of air-drying and freezing were investigated using two soils, one being a forest soil (FS) high in organic matter and the other being a sterile soil (SS) low in organic matter. Soil P was fractionated using a modified Hedley fractionation method to examine the changes of phosphorus fractions induced by air-drying and freezing. Generally, there were no significant differences of total phosphorus among the three treatments (CV% &lt; 10%). Compared with field moist soils, freezing the soil evoked few changes on phosphorus fractions except that the resin-P increased in FS soil. On the contrary, air-drying significantly changed the distribution of phosphors fractions for both soils: increased the labile-P (especially resin-P) and organic-P (NaHCO<sub>3</sub>-Po, NaOH-Po and Con.HCl-Po) at the expense of NaOH-Pi and occlude-P (Dil.HCl-P and Con.HCl-Pi). Resin-P significantly increased by 31% for SS soil and by 121% for FS soil upon air-drying. The effect of air-drying seemed to be more pronounced in the FS soil with high organic matter content. These results indicated that drying seem to drive the P transformation form occlude-P to labile-P and organic-P and accelerated the weathering of stable P pool. This potentially could be significant for soil P supply to plants and P losses from soils to surface waters under changing patterns of rainfall and temperature as predicted by some climate change scenarios. &nbsp;


2009 ◽  
Vol 60 (2) ◽  
pp. 124 ◽  
Author(s):  
Alan E. Richardson ◽  
Peter J. Hocking ◽  
Richard J. Simpson ◽  
Timothy S. George

Phosphorus (P) is an important nutrient required for plant growth and its management in soil is critical to ensure sustainable and profitable agriculture that has minimal impact on the environment. Although soils may contain a large amount of total P, only a small proportion is immediately available to plants. Australian soils often have low availability of P for plant growth and P-based fertilisers are, therefore, commonly used to correct P deficiency and to maintain productivity. For many soils, the sustained use of P fertiliser has resulted in an accumulation of total P, a proportion of which is in forms that are poorly available to most plants. The efficiency with which different P fertilisers are used in agricultural systems depends on their capacity to supply P in a soluble form that is available for plant uptake (i.e. as orthophosphate anions). In addition to fertiliser source, the availability of P in soil is influenced to a large extent by physico-chemical and biological properties of the soil. Plant access to soil P is further affected by root characteristics (e.g. rate of growth, specific root length, and density and length of root hairs) and biochemical processes that occur at the soil–root interface. The ability of roots to effectively explore soil, the release of exudates (e.g. organic anions and phosphatases) from roots that influence soil P availability, and the association of roots with soil microorganisms such as mycorrhizal fungi are particularly important. These processes occur as a natural response of plants to P deficiency and, through better understanding, may provide opportunities for improving plant access to soil and fertiliser P in conventional and organic agricultural systems.


Author(s):  
Khadraji Ahmed ◽  
Bouhadi Mohamed ◽  
Ghoulam Cherk

Background: Growing chickpea (Cicer arietinum) plants is affected by several environmental constraints as osmotic stress and nutrients deficiency particularly phosphorus (P). For other legume species, it was confirmed that P deficiency affects negatively their rhizobial symbiosis. The purpose of this study was to assess the effect of soil available P level on chickpea-rhizobia symbiosis under field conditions at Oualidia region of Morocco. Methods: Ten farmers’ fields with different soil available P levels were considered to carry out this study based on samples of 10 plants per plot. Result: The results showed that the plants from soil 7, with the lowest pH and the highest available P level (23.52ppm), presented high shoot dry weight (38.3 g/plant). Meanwhile the soil 5 with the lowest available P content showed low plant growth. The shoot P content was positively linked to soil P level but nodule biomass showed an irregular variation with soil available P level. Furthermore, it was confirmed that adequate plant P nutrition results in high chickpea yield and it was the case for plants from soil 7 presenting a mean yield of 62 seeds per plant). Finally, strong correlation was noted between yield and phosphorus concentration in soil (r=0.94).


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