A model was constructed that applied scaling factors to reduce NH₃ loss in terms of soil type, fertiliser type, rate and management, rainfall and crop growth. The model was assessed against measured NH₃ loss reported in a range of contrasting studies. The approach gave accurate estimates in the majority of case studies and appears to be a reliable tool for estimating NH₃ loss after fertiliser application to moist soil.

Phosphorus is often a limiting nutrient in Australian agriculture, the limitation reflecting low availability to plants of the majority of soil phosphorus, including organic forms which we know relatively little about. Here we provide evidence that the organic phosphorus in a soil type used widely for cropping consists of a small, rapidly cycling component and a large, slowly cycling component. Understanding how phosphorus gets trapped in the slowly cycling form may eventually facilitate more efficient use of phosphorus fertiliser.

Soil quality assessment was carried out under long-term rice-based cropping system of farmers’ field for three dominant Soil Orders in Eastern India. Twenty seven no. of soil physical, chemical and biological attributes were used in this assessment. Four to five key indicators were screened through PCA and discriminate analysis. However, 1 or 2 indicators, mostly biological and chemical were validated for predicting the system yield.

Knowledge of the factors influencing soil carbon stabilization is required to identify soils with capacity to sequester atmospheric CO₂. Particle size fractionation studies, using 58 New Zealand soils (representing difference soil Orders and land use histories), showed that the clay fraction of fine-textured soils may be under-saturated with C. Therefore, these soils could be targeted when developing C sequestration strategies.

Compared with the conventional tillage (CT) treatment, no tillage (NT) reduced the 3-year average yield-scaled CO₂ emissions by 41% with no reduction in wheat yield. CO₂ was significantly and positively related to total nitrogen, soil organic matter, soil enzymes, soil temperature and total pore space. The change from CT to NT treatment resulted in significant changes in the soil’s properties. Multiple linear regression analysis in NT plot explained 85% (P < 0.05) of the CO₂ variability and 80% (P < 0.001) in case of CT plot.

Digital soil models and maps have been developed for pre-European (pre-vegetation clearing) levels of soil organic carbon (SOC) over NSW, Australia. A loss of ~0.53 Gt SOC has occurred since clearing over the entire state (0-30 cm depth). The extent of SOC decline was highly dependent on the climate – parent material – land-use regime, being greatest at 44.3 t/ha under cooler (moist) conditions over mafic parent materials under regular cropping use.

It is widely suggested that farmers can increase organic matter (carbon, C) storage in soil by using different management practices, and that this will counteract rising levels of atmospheric CO₂ as well as improve soil fertility. We measured organic C in 615 farm paddocks across Victoria and found that C levels were very strongly related to climate, weakly related to soil type, very weakly related to type of farming (cropping, mixed farming, sheep and beef, dairy), and not measurably related to farm management practices. Because management effects are very small, they cannot be measured unless climate and soil effects are accounted for.

Management of dryland salinity and associated water resources in Western Australia is an important issue for maintaining productive land and agricultural sustainability. This investigation focuses on the detailed processes of water and salt movement in a saline groundwater discharge area. Annual water and solute balances are determined and the processes that mobilise and discharge saline groundwater in a small groundwater seepage area in WA were determined via a field observation. These provided useful information for the estimation of catchment salt balances and time scales of salt discharge.

A new approach was developed to obtain spatially discrete estimates of pasture growth and seasonal patterns across New Zealand. This was based on Land Use Capability Classes, derivation of representative soil profiles and deterministic modelling using the Agricultural Production Systems Simulator (APSIM). These pasture growth curves can be used with farm system models to investigate the effect of land use and management changes at regional scales.

Continuous monitoring of soil moisture by using moisture sensor can provide valuable information for the understanding and protection of water resources. There are standard equations available to convert sensor’s output to moisture content. However, sensor’s output can vary according to the soil bulk density and clay content in the soil profile. So, to obtain accurate monitoring, sensors especially the capacitance sensors need to be calibrated for the specific soil types.

Maleic-itaconic acid copolymer has been claimed to reduce soil P-fixation. A theoretical consideration based on equilibrium constants of various reactions shows that the claim is false. The copolymer has much lower chelating power with soil Al, Fe and Ca cations than the chelating of these cations with phosphate ion in the soil. Hence the copolymer cannot reduce soil P-fixation.