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Red soils cover 21% of China's surface: some 2.10 6 km 2 . Much of the area is hilly. Rice grows mainly in the lowlands. Only a fraction of the uplands in the red soil area is cropped, but yields are low due to inadequate topsoil as a result of erosion and nutrient mining. The remainder is wasteland that is not used for cropping and a little for grazing. But these areas have a high agricultural production potential if some constraints are removed. The World Bank has set up a major project named “China Red Soil II”. It comprises a total area of over 9.10 4 ha for development or rehabilitation, with 215 small watersheds including one named Qingshishan. Techniques of system analysis and optimization are applied to this watershed, and a watershed development planning model (QINGS) has been created. QINGS includes seven objectives, 32 activities and some constraints, two scenarios; three land use forms and two irrigation systems are available to the model for selection. This complexity provides a web of possibilities and there can be many solutions for suitable development. By running QINGS a number of times for successively more specific goals, a window of opportunities is established where land use practice is the key factor to development and where all goals are met to a certain degree. Feasible solutions can then be identified in which reduction of soil erosion, increased income and sustainability in land use are combined. Local farmers and technical officers can identify and accept the best compromise. QINGS is a tool for watershed developers that allows them to quantify opportunities and constraints, and set specific targets for developments with the local population. Results of QINGS can empower local farmers in negotiations with watershed developers. After 5 years of red soil development supported by the World Bank Project, various activities were initiated, including new crops (e.g. bamboo), trees (e.g. mulberry), livestock, fish and pearl production, and an ecological and social benefit forest. Infrastructure was improved (such as irrigation system, traffic conduction, biogas ponds and so on). The year 2000 total net income is 870,000 yuan, compared with 265,000 in 1994 before the project. Before the project, the forest cover rate was 9%, now it is up to 50%; soil erosion is at low level, and water supply has increased the length of the secure growing season by more than 50 days. The social employment conduction is also improved, especially the employment of rural women. The whole structure of agro-ecology system is optimized.

To cope with estimated population growth in Asia, attainable rice yield potential must increase in the irrigated lowlands. At odds with this goal is the fact that yield potential of released high yielding rice varieties has remained constant since the release of IR8 in the late 1960s, although yield per day increased as a result of shorter growth duration and host plant resistance was improved. For example, highest rice yields of IR72 (released in 1987) were 6 and 9.5tha-1, in the 1991 wet season and the 1992 dry season, respectively, in a tropical environment with good agronomic management. These yields are comparable but no higher, than the highest yields attained by IR8 in the same environment more than 20 years ago. Detailed growth analysis from these recent studies allowed us to improve an eco-physiological model for rice growth. Subsequent simulations demonstrated accurate prediction of wet and dry season rice yield. The model was then used to evaluate the effects of global climate change as expected by the year 2020. Changes in temperature and atmospheric CO2 had relatively small effects on simulated rice growth and yield compared with (1) the impact of crop management practices in high-yielding environments and (2) genetic improvement that could further increase yield potential. Varieties with a longer grain filling duration will be needed to increase the yield plateau and to reverse negative effects of increased temperature.

There is potential in cultivating cowpeas (Vigna unguiculata (L.) Walp.) in rice-based cropping systems in the humid tropics as a source of proteins for humans, forage for ruminants, and for improvement of soil fertility. Seasonal and yearly variability is, however, a major constraint. A statistical stability model and a mechanistic simulation model were used to quantify yield variability of early and medium maturity groups of cowpea cultivars in pre- and post-rice environments at Los Banos, Philippines. Four field experiments, with 24 cultivars in each experiment, were conducted in pre- and post-rice environments, to determine the response of the cultivars to varying moisture and to water table depth regimes, and a stability analysis was performed across the regimes using a statistical model. In the post-rice environment, irrespective of moisture and water table depth regimes, the medium maturing cultivars tended to outyield early maturing cultivars, whereas in the pre-rice environment, early maturity demonstrated a distinct yield advantage. The statistical stability model indicated that medium maturing cultivars performed well in high-yielding environments, whereas in low-yielding environments their yields were comparable with those of early maturing types. However, results of the statistical stability model are limited because of the short time series of basic data. To broaden the analysis, a simulation model of the cowpea crop was calibrated and validated for its performance. Measured and simulated dry weights of crop parts (leaves, stems and pods) and soil moisture contents at 10-cm soil depths throughout the growing season indicated satisfactory performance of the simulation model. Long-term simulation results using the validated model indicate that TVX1948-012F (medium maturity) performs betters (800–2250 kg ha−1) than IT82D-889 (early maturity) (430–1620 kg ha−1) with a fluctuating shallow water table in the post-rice environment, whereas IT82D-889 is superior (80–1150 kg ha−1) to TV1948-012F (30–1150 kg ha−1) in the pre-rice environment. Yields are highest and least variable for the 15 January planting in the post-rice environment, and for the 15 April planting in the pre-rice environment.

In this chapter, the authors develop the concept of the endophyte as a unique candidate for genetic engineering for the purpose of conferring resistance. Endophytes should be viewed as an important genome for crop protection. Genetic engineering of well-chosen endophytes offers several advantages over other means of imparting insect and disease resistance to crops: the freedom of interspecific gene movement expands possibilities beyond that of traditional breeding. Scientists at Crop Genetics International (CGI) have chosen the bacterium Clavibacter xyli subsp. cynodontis (Cxc) for commercial development to produce and deliver biopesticides in planta. Since Cxc is the only endophyte being engineered for commercial development, it will serve as the chapter's primary example of potential benefits of the endophyte approach to crop improvement. CGI is continuing product development research to identify appropriate market opportunities for endophyte-based crop protection products.

There is a growing interest in cultivating wheat in Southeast Asia for reduction of the drain of foreign exchange and for crop diversification. A crop growth model was used to establish potential and rainfed yields of wheat following rice in different parts of this region. A comparison of measured and simulated yields indicated satisfactory performance of the model. The results indicate that the yield potential of irrigated wheat is between 3·0 and 5·0 t ha−1 between 10 S and 23 N latitude at sea level, but it is higher at altitudes between 500–2000 m. Such yields are stable and relatively insensitive to sowing date. Rainfed yields are lower, and have a high year-to-year variability. The gap between potential and water-limited grain yields is small if wheat is sown towards the end of the rainy season on a deep and well-drained soil.

For the simulation of organ formation and assimilate partitioning, information is required on the current level of activities like CO2 assimilation and the growth of various organs, as well as state variables such as leaf and root wt., N content and carbohydrate reserves and exogenous variables like radiation and temp. This information may be retained in auxiliary state variables by considering the dynamic equilibrium between growth of roots and shoots. Auxiliary state variables are not tangible quantities but mathematical artefacts of the simulation program; it is speculated that in real plants similar information may be retained and transferred by the hormonal system. A hormonal system is a communication system and such systems may be analysed either in terms of means (of the hardware used) or in terms of purpose (of the messages transferred). In dynamic models of crop growth, interest should be focused on the latter. Wheat, maize and ryegrass are used as examples. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Summary Maize plants hydroponically grown on nutrient solution were used to study the effect of alterations in N supply on N concentrations in the organs as related to the ability of biomass production. Omission of nitrate from the nutrient solution induced in the vegetative organs a breakdown of nitrogenous compounds which were partly redistributed towards the ears. These processes took place more at the expense of membrane proteins than of the buffer-soluble proteins and resulted in N concentrations lower than the theoretical minimum; then the biomass production stopped. Re-supply of nitrate to young N-starved plants induced an increase of N concentrations in all plant parts and the resumption of biomass production. The newly produced amount of membrane proteins was larger than that of buffer-soluble proteins. However, the ratio of buffer-soluble to membrane protein concentrations in mature leaves did not return to the original value. It was concluded that re-supply of nitrate resulted in a recuperation of N-starved plants to a restricted extent.