Effects on Nitrogen and Phosphorus in Agricultural Soils Following the Application of Slurry Amended with Additives

This poster elucidates the experiments related to the first objective of a PhD focussed on the use of amended organic fertilisers (manures/slurries) in agricultural soils. Nitrogen (N) and phosphorus (P) are the most yield-limiting nutrients in many soils. Manures and slurries could represent valid alternatives to inorganic fertilisers to replenish nutrient offtake via harvested crops. Inoculation of slurry using additives, such as Slurrybugs™ and Slurrybooster™, can enhance the nutrient value of slurry, due to the action of microorganism and enzymes within the additives.

Impact of fertilisers on soil properties and biomass yield under a long-term sweet sorghum cropping system

A continuous long-term field experiment (2008–2018) was conducted in Xinjiang, north-western China, to assess the impact of farmyard manure (FYM) and inorganic fertilisers on the sustainable biomass yield of sweet sorghum cultivar (Xingaoliang No. 3) and soil chemical properties. Seven treatments, associated with nitrogen (N), phosphorus (P), potassium (K), FYM, and their different combination, were compared with the control plot (CK). As a result, the treatments NP, PK, NK, NPK and NPKM significantly increased the average biomass yields by 30–48% over CK. The 12 t/ha FYM per year with NPK (NPKM) increased both the yield and total soluble solids (T_SS) by 48% and 7.9%, respectively, while the 18 t/ha/year application rate of FYM had an adverse effect on yield. Stem T_SS, soil available N and K for all treatments decreased while soil organic carbon, soil total salt and the available P for FYM applied treatments increased over the years. The soil pH stabilised at 7.8–8.2 at the end. In conclusion, the 12 t/ha/year of FYM is the most efficient rate for a single application or incorporation with inorganic fertilisers. A more reasonable application rate of N and K fertiliser to increase the yield and irrigation rate to reduce soil salt needs for further investigation.

Insect left-over substrate as plant fertiliser

The production of insect protein as human food and livestock feed (entomophagy) may provide a more environmentally beneficial alternative to traditional animal agriculture. However, the resulting waste product from insect production has resulted in large accumulations of left-over substrate and frass. Due to its nutrient and microbial profile, this left-over product has the potential to be utilised as a biofertiliser for high value crop production. Studies have been conducted using the frass of various insects (e.g. black soldier flies, houseflies, and mealworms) to monitor its impact on crop productivity. Overall, frass tends to have similar or better results when compared to inorganic fertilisers, especially when combined with them. Aside from productivity and growth, frass may also preserve soil fertility by decreasing leaching and infiltration, and reducing the prevalence of disease and pathogens. In addition, chitin found in frass also has beneficial properties for plant/crop growth and disease resistance. Monitoring the dietary inputs of industrially reared insects may be the best way of mitigating the potential negative impacts of frass application, such as increased electrical conductivity and heavy metal toxicity. No single study confirms all of these benefits at once. Future studies should focus building onto these results by demonstrating systems levels benefits.

Quality and Economics of Bt Cotton as Influenced by Compost, Organic and Inorganic Fertilisers

Agricultural application of urban waste as nutrient source for plants and as soil conditioner, is the most cost effective option of waste management because of its advantages over traditional means such as land filling or incineration. Composting is an attractive alternative of urban waste recycling. Intensive cropping and indiscriminate fertilizer application depleted available NPK in almost all soils in India. Hence, replenishment of shoveled out nutrients is very essential, especially when exhaustive crops like cotton is cultivated. With this backdrop an experiment was conducted during kharif, 2014 carried out at College Farm, College of Agriculture, PJTSAU, Hyderabad, India to find the effect of combined application of municipal city compost with inorganic fertilisers on the yield, quality and economics of Bt cotton. The experiment was laid out in randomised complete block design with three replicates and eleven treatments viz; 100 % NPK alone (RDF: 150: 60: 60 kg NPK ha-1)100% NPK + FYM (farmers practice) and 100 %, 75%, 50% NPK integrated with 3 levels of Godavari Gold (GG) @ 1.25, 1.875 and 2.5 tonnes ha-1 respectively. The results indicated that Bt cotton registered significantly higher yield attributes and yield with the integrated application of 100 % NPK + 2.5 t ha-1 of Godavari Gold compost as compared to 100% NPK alone, 100% NPK + FYM (farmers practice) and 75 % RDF (112.5-45-45 kg NPK ha-1) and 50 % RDF (75-30-30 kg NPK ha-1) integrated with Godavari gold compost @ 1.25, 1.875 and 2.5 tonnes ha-1.There were no significant differences in quality parameters. Highest gross, net returns and B: C ratio was accrued with the application of 100 % NPK + 2.5 t ha-1 of Godavari Gold compost.

Effect of organic amendments and inorganic fertiliser application on nitrogen use efficiency and denitrification in controlled and field conditions

<p>The amount of bioavailable nitrogen is directly linked to anthropogenic activity (Kuypers, Marchant, & Kartal, 2018), particularly with the intensive application of synthetic nitrogen fertilisers. Although high nitrogen inputs are required to support the ever-increasing need for food production, nitrogen use efficiency is in many cases low, to the extent that even with extra nitrogen inputs over time, increases of food production are small and slow (Battye, Aneja, & Schlesinger, 2017).</p><p>It has been suggested that roughly 40% of reactive nitrogen is denitrified in the soil (Seitzinger, et al., 2006), and most of the reactive nitrogen that results from human activities is removed by denitrification, with consequent production of N<sub>2</sub> and N<sub>2</sub>O. However, even if most reactive N forms are removed by denitrification, this is an indicator that N use efficiency is not at optimum levels.</p><p>A study is being conducted in field and controlled conditions, that aims to understand denitrification and nitrogen use efficiency in a long-term experiment (running continuously since 2013) at Rothamsted Research. The experiment was designed to provide a clearer look at the effect of applications of organic amendments and/or inorganic fertilisers on nitrogen dynamics and crop yields in a conventional cereal-based cropping system.</p><p>Simultaneously, using yield data from the same trial, we aim to understand a) if the application of organic amendments leads to a reduction of the nitrogen threshold for optimum yields and, by using a modelling approach, b) if the eventual higher yields obtained with organic amendment application are due to the effect of the extra nutrients contained in the amendment or to some other effect caused by the amendments.</p><p>Soil and gas samples are being collected from a) different treatments of the field experiment (four different organic amendments: anaerobic digestate, compost, farmyard manure, straw and unamended control; and different nitrogen application rates; area of each plot: 54 m<sup>2</sup>) to assess nitrogen dynamics, and b) from soil columns (height 35 cm; width 25.5 cm)  placed in a controlled environment using soil collected from the same trial. Different measurements are being taken including leachate (measurements of mineralised nitrogen), microbiology and gas emissions (using a Picarro device that measures NH<sub>3</sub>, N<sub>2</sub>O, CO<sub>2</sub>, CH<sub>4</sub>, O<sub>2</sub>, H<sub>2</sub>O). Simultaneously, underground sensors are being used to understand moisture and temperature evolution in the soil column, while electrochemical nitrate sensors are being used to understand nitrate dynamics before and after application of organic amendments and inorganic fertilisers.</p><p>With this, we aim at having a better understanding on denitrification processes and nitrogen use efficiency issues that may occur when using a joint regime of organic amendments and inorganic fertilisers. The main objectives of the project are the validation of the effect of organic amendments in the Fosters long-term experiment and the quantification of nitrogen gas emissions with the application of organic amendments and nitrogen fertilisers.</p>

Effects of Cowpea-Amaranth Intercropping and Fertiliser Application on Soil Phosphatase Activities, Available Soil Phosphorus, and Crop Growth Response

Low available soil phosphorus (P) is associated with its immobility, which renders it unavailable for plant uptake. In addition, farmers normally apply inorganic fertilisers to legumes to activate soil-bound phosphorus using root exudates. Sufficient soil mineral nutrition is key to sustainable crop production, and hence food and nutritional security. The aim of this study was to quantify the acid and alkaline phosphatase activity as an indicator of P supply and availability under varying levels of nitrogen, phosphorus and potassium (NPK) fertilization and different cropping systems. An intercropping (cowpea and amaranth) and fertiliser (control, 25%, 50%, and 100% of the recommended NPK levels) field trial was laid out in a 2 × 4 factorial treatment structure in a completely randomized design (CRD) with four replications. There was higher acid and alkaline phosphatase activity in the rhizosphere of cowpea and amaranth grown as sole crops compared to those from intercropping. The cowpea and amaranth plants grown without fertiliser or 25% NPK had the highest rhizospheric phosphatase activity, while 100% NPK application exhibited the least. The markedly higher phosphatase activity from the low fertiliser application treatments indicates the possible stimulation of microbial activity to supplement P demands for the crops. The study revealed that the application of lower rates inorganic fertilisers in a legume intercrop stimulates the activity of the phosphatase enzymes, which can subsequently liberate soil-bound phosphorus. Plant tissue phosphorus concentration of cowpea and amaranth plants increased proportionately to the increase in fertiliser application up to 50% of the recommended NPK level. The land equivalent ratio (LER) was greater than 1, indicating that it is more beneficial to intercrop cowpea and amaranth as opposed to growing them as sole crops. Overall, the application of NPK fertilizer to amounts of up to 50%, based on the results of this study, appear to be better than 100% in terms of biomass accumulation and phosphate activity.