Eight tonnes ha -1 of stubble were used to mulch spring wheat (Triticum aestivum) on a fine textured soil with the aim of controlling both transpiration and soil evaporation during the wet pre-anthesis phase to increase moisture supply during grain filling in the eastern wheatbelt of Western Australia. Mulching reduced leaf area per plant by reducing the culm number; consequently the green area index was reduced. Reduced culm number was associated with low soil temperature which at 50 mm depth averaged 7°C lower under the mulched crop relative to the control crop in mid-season. The smaller canopies of the mulched crop used 15 mm less water than those of the control before anthesis; this difference in water-use was due equally to reduced transpiration and soil evaporation. However, the mulched crop was unable to increase ET during grain filling, a response associated with the persistence of low soil temperature for most of the growth period. Hence, total ET for the season was significantly lower (18mm) under the mulched crop than the control crop. At harvest, mulching did not have significant effects on total above-ground dry matter and grain yields, but it increased water use efficiency for grain yield by 18%, grain weight by almost 17% and available moisture in both uncropped and cropped plots by an average of 43 mm.To determine whether there was any residual effects of soil treatment on moisture storage during the summer fallow period, soil moisture was monitored both in cropped plots and uncropped plots, that were either mulched or unmulched during the growing season, from harvest in October 1988 until next planting in June 1989. Available moisture at next planting was correlated with moisture storage at harvest despite the differences in run-off, soil evaporation and fallowing efficiency (increase in moisture storage as a percentage of rainfall) between treatments during fallowing. Therefore, the mulched treatments had more moisture available (30 mm), mostly as a result of less water use during cropping in the previous growing season, than the unmulched treatment.The study shows that mulching may be used to restrain both transpiration and soil evaporation early in the season to increase availability of soil moisture during grain filling. Secondly, mulching during the previous growing season had little effect on soil moisture during the summer fallow period, however, the moisture saved by mulching during cropping was conserved for the following season. These results indicate the importance of evaluating mulching of winter crops in terms of crop yield in the subsequent growing season as well as in the current season in which the soil was treated.120 Yunusa et al.

This chapter describes the production environments; phenological adaptation to the environment; flowering response to photoperiod and temperature; and the impact of abiotic stresses (water availability, waterlogging, temperature, nutrient toxicity including salinity and sodicity, and mineral deficiency), diseases, and management (sowing time, weed control, and harvesting method) on adaptation of lentil. Improvement of adaptation through understanding genotype by environment interactions in lentil is discussed. To improve adaptation, the key traits that facilitate increased production (level and reliability of seed production), farming system benefit and price (quality of seed), or reduce cost must be identified, quantified and addressed through improved production technology and breeding. More specifically, profitability is a culmination of a species interaction with the environment, in particular the quantity and distribution of rainfall and temperature which influences the length of growing season, soil characteristics and biotic stresses, and cultural practices. Farming system benefits include those involved with rotation, such as providing a disease break or improving soil nutrition, weed management, and the timing and simplicity of total farm operation.

This chapter reviews the effects of water deficits on growth and yield of lentil and explores the genetic and agronomic options to minimize the effects of drought on dry matter (DM) production and seed yields.

Plant productivity is directly affected by the capacity of the root system to forage for soil resources. An enhanced understanding of root-soil interactions provides the potential to improve crop performance in specific soil environments. Interactions between roots and soil are, however, complex. The root-soil environment is heterogeneous and difficult to visualise and measure, root architecture and root growth responses are complex and dynamic, and processes from the ionic and rhizosphere scale right up to the whole crop and even catchment scale are involved. For these reasons, pot experiments are used in root studies to simplify the environment, target specific interactions and aid with visualisation and measurement. Significant challenges exist, however, in relating pot studies to the field, requiring upscaling from a spatially confined and artificially contrived environment to the reality of a more complex cropping environment. Simulation models provide an opportunity to upscale complex root-soil interactions from the pot to the field, but to do so they must represent the way that plant roots explore a restricted pot environment. In this study ROOTMAP, a 3D functional-structural model of root growth and resource capture, was modified to enable the simulation of barriers in soil, and the interaction of plant roots and soil water and nutrients with those barriers. This barrier-modelling utilises custom coding, with the support of Boost.Geometry (Generic Geometry Library) where appropriate. The barrier approach defines the 3D shape and location of any number of what are termed Volume Objects. Roots and soil can be: wholly contained within one Volume Object such as in the case of roots growing in a pot; a plant can have roots distributed between two Volume Objects such as in a split-pot experiment; and they can be wholly outside one or more Volume Objects for simulating the presence of rocks or other hard objects in soil. Volume Objects can be wholly impermeable, such as; pot walls that contain roots within them, or impermeable rocks or hardpan layers that roots grow around. Volume Objects can also have varying degrees of permeability for representing layers or areas in soil that have varying degrees of hardness and varying root penetrability. In this initial version of the code, barriers or objects can be represented as rectangular prisms, giving flat barrier layers or square or rectangular objects such as root/rhizo boxes, or as cylinders, representing curved pots or smooth curved objects in soil. The barrier modelling code calculates the deflection of a root tip when it intersects a boundary, representing the way that plant roots grow around and along object surfaces. It also calculates the effect of semi-permeable objects in soil on root growth into and around those objects. Water and nutrients are distributed through the soil environment by use of a variable 3D grid of sub-volumes or cells. The water and nutrient routines then search for the presence of a barrier or wall (Volume Object) intersecting each cel...

Both PU and PC increased maize yield, water use efficiency (WUE), and partial factor productivity from applied N (PFPN), relative to CK. PC increased maize yield more than PU, and had higher soil organic carbon (SOC) content than PU, which was mainly due to the decline in SOC stocks in the 250–2000, 53–250, and <53 μm soil aggregates. The soil bacterial community structure was driven by SOC, C: N ratio, total nitrogen (TN), pH, microaggregates, clay and silt in CK, and by larger macroaggregates and mean weight diameter in PC and PU. Both PC and PU significantly changed soil bacterial community beta diversity, and decreased both positive and negative links of the co-occurrence network, relative to CK. Better soil nutrient conditions in PC explained the small number of positive and negative links between soil bacteria. Our results suggest PM improves maize yield, water and nitrogen use efficiency, and soil aggregate stability while alleviating bacterial competition. However, the reduction of SOC and pH caused by PM still needs our attention. PC alleviates the decline of soil fertility and soil acidification and has higher yield relative to PU. Therefore, we proposed PC is a potential agricultural measure that can replace PU on the Loess Plateau.