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Conventional tillage and crop establishment methods for the rice–wheat (RW) system are input intensive (water, labour and energy). About 24.5 million tonnes of rice residues are burnt every year on farms in north-western India before sowing of wheat, causing air pollution and soil health degradation. Therefore, alternative tillage, crop establishment and residue management practices are needed for long-term sustainability of the RW system. A 4-year field study evaluated four tillage and crop establishment methods in rice (in main plots) and three tillage and rice residue management methods in wheat (in subplots) for their effects on yield, soil fertility, and profitability of the RW system. Average rice yields were similar under conventional puddled transplanted rice (PTR) and conventional till dry seeder rice (CTDSR). Both of these treatments produced significantly greater yields (10–16%) compared with zero till DSR (ZTDSR) and ZT machine transplanted rice in non-puddled soil, respectively, regardless of tillage and straw management methods in the previous wheat crop. Wheat yields in ZT wheat (ZTW) with 100% surface retention of rice residue (+R) were significantly greater than conventional till without residue retention after 2 years of experimentation, and accompanied by significant increases in macro-nutrient (potassium) availability in soil. The ZTW−R (no residue) treatment produced 15% lower wheat yield than ZTW+R. System yield was highest in CTDSR-ZTW+R, which was 5% higher than the conventional practice PTR-CTW−R, resulting in Rs 17 000 ha−1 greater net returns. The sustainability of conventional rice–wheat production systems in northwestern India has become a major concern for addressing the issues of energy, labour, water scarcity and quality. Resource conservation technologies such as zero tillage with residue retention showed higher productivity, profitability and potential in improving the soil health. The adoption of sowing of wheat into rice residues can achieve high crop productivity and income, while avoiding ill effects of straw burning on the environment. [ABSTRACT FROM AUTHOR]

In this study, a uniformly distributed mathematical model for the self-heating process within compost piles is formulated and investigated. It consists of mass balance equations for oxygen and energy as well as the heat-generation processes due to both biological and chemical activities. This model is an extension of the study of Luangwilai et al. [2013] which consists of only biological activity. The singularity and degenerate Hopf bifurcation theories are used to determine the loci of different singularities: the isola, cusp, double-limit points and boundary limit set as well as the double-Hopf, generalized Hopf (Bautin) and Bogdanov–Takens bifurcations. In this investigation it is found that these loci separate the secondary parameter plane into twenty-two regions of different steady-state solution behaviors, whereas the model in the earlier study reported only eight regions. With more topological detail in the parameter space, a clearer understanding of the thermal behavior of a compost pile can be obtained, thus assisting compost operators in controlling the temperature within the pile more effectively: for example, achieving desirable elevated temperature range for ideal composting conditions via periodic solutions and S-shaped solution branch, or alternatively, understanding conditions, if not monitored carefully, that can also increase the likelihood of spontaneous ignition within the pile. [ABSTRACT FROM AUTHOR]

To reduce the human effort involved in walk‐behind paddy transplanter operation, a remote‐control system consisting of an electronic control unit (ECU) was designed and developed. A separate remote handheld wireless kit was developed to control the ECU. The deviation from a straight‐line path was measured by mounting a real‐time kinematic global satellite navigation system on the transplanter to provide a real‐time plot of the navigation path of the transplanter. The results from the field evaluation revealed that the system worked properly with an effective field capacity of 0.16 ± 0.03 ha h−1 with a field efficiency of 73.05% ± 0.35% at 1.8 km h−1 in sandy loam soil. The mean deviation from the predefined straight path was 0.227 ± 0.041 m for the remote‐controlled transplanter as compared to 0.171 ± 0.041 m for a manually operated transplanter. The net benefit of using the transplanter with the developed system was $40 per hectare and $2084 per year with a payback period of 2.7 years. The developed remote‐control system reduced the drudgery/fatigue by up to 90% and increased the operator's work efficiency. In addition, an operator sitting in a safe and comfortable environment outside the puddled field improved the field capacity of paddy transplanters by up to 10% and helped minimize the effects of labor shortage during the transplanting season. [ABSTRACT FROM AUTHOR]

We consider the numerical solution of competitive exothermic and endothermic reactions in the presence of a chaotic advection flow. The resulting behaviour is characterized by a strong dependence on the competitive reaction history. The burnt temperature is not immediately connected to simple enthalpy calculations, so there is a subtlety in the interplay between the major parameters, notably the Damköhler number, the ratio of the heats of exothermic and endothermic reactions, as well as the ratio of their respective activation energies. This paper seeks to explore the way these parameters affect the steady states of these reaction fronts and their stability. [ABSTRACT FROM AUTHOR]

The activated sludge process is widely used to treat both municipal sewage and a variety of industrial wastewaters. We investigate the steady-state behaviour of an activated sludge process. We use the activated sludge model number one, an internationally accepted model, to describe the biochemical, biological, and physical-chemical phenomena that occur inside the bioreactor. The treatment configuration consists of a single aerated reactor attached to a settling unit. Continuation methods are used to determine the steady-states of the model as a function of the hydraulic residence time. From these solutions we construct important operational parameters including the chemical oxygen demand, total suspended solids and total nitrogen. These are determined inside the bioreactor, in the effluent stream and in the wastage stream. We show that there are two critical values of the hydraulic retention time. As the hydraulic retention time is increased through the first critical value heterotrophic biomass become viable. This bifurcation is associated with a substantial decrease in the chemical oxygen demand in the effluent stream and a corresponding increase in both the total suspended solids and total nitrogen in the reactor. Autotrophic biomass become viable as the hydraulic retention time is increased through the second bifurcation point. Associated with this bifurcation there are dramatic changes in the concentration of soluble ammonium nitrogen and soluble nitrate/nitrite inside the reactor; the former being converted to the latter. Of particular practical interest is the value of the hydraulic retention time at which the chemical oxygen demand in the effluent stream is equal to a preset target value. We investigate how this value varies as either the composition of the influent stream or the recycle ratio is varied. [ABSTRACT FROM AUTHOR]

Cotton–wheat (CW) is an important cropping system in South Asia. Wheat yields under a conventional CW system are generally lower compared to a rice–wheat system due to delayed seeding. Relay seeding of wheat can help timely sowing, capturing residual soil moisture of last irrigation to cotton, and increase the productivity and profitability of CW system. The field experiment included two Bt-cotton genotypes having different canopy cover (RCH 776 and MRC 7017), two types of relay seeders (RSs) for cotton planted at 67.5-cm and 101-cm row spacing and four types of relay seeding methods (manual broadcast, strip rotor (SR) and zero-till double disc and conventional till). Relay planting of wheat allowed one additional boll picking, which increased seed cotton yield by 12% compared with conventional tillage wheat. Cotton genotypes and RSs had no effect on emergence and yield of wheat. The RSs with SR and zero till double disc furrow openers performed better in terms of wheat emergence and grain yield compared to zero-till tine openers. Under relay seeding, wheat sowing was advanced by 31 days, which increased grain yield by 18.8% compared with conventional tillage practice. Net returns from the CW system with relay seeding of wheat were higher by US$ 311 to 425 ha−1 compared with the conventional CW system. [ABSTRACT FROM PUBLISHER]

Cotton–wheat (CW) is the second most important cropping system after rice–wheat in South Asia. Sowing of wheat after cotton is usually delayed due to late pickings coupled with time needed for seedbed preparation, resulting in low wheat yield. Lack of suitable machinery is a major constraint to direct drilling of wheat into the heavy cotton stubbles. An innovative approach with much promise is the ‘2-wheel tractor-based self-propelled relay seeder’ with seed-cum-fertilizer attachment. On-farm trials were conducted at four locations during 2009–2010 and at 10 locations during 2010–2011 to evaluate the following four wheat establishment methods in CW-dominated areas of south-western Punjab, India: (1) zero till seeding in standing cotton using a self-propelled relay seeder, (2) relay seeding in standing cotton with a manual drill without prior tillage (2010 only), (3) relay broadcast seeding in standing cotton following light manual tillage and (4) conventional sowing of wheat after cotton harvest (conventional tillage and sowing with a seed–fertilizer drill). Planting of wheat under conventional practice was delayed by 20–44 days compared with relay seeding. Seed cotton yield was also significantly higher with relay seeding due to opportunity for one additional picking. Yield of wheat sown with the self-propelled relay seeder was 41.2% and 11.8% higher than with conventional practice in 2009–2010 and 2010–2011 respectively. The increase in wheat yield under relay seeding of wheat was primarily due to higher spike density and more grains per spike. The net income from the CW system was 28.2% higher for the self-propelled relay seeder than with conventional sowing. [ABSTRACT FROM AUTHOR]

We consider travelling wave solutions of a reaction–diffusion system corresponding to a single-step homogeneous premixed combustion scheme competitively coupled with an endothermic reaction. Properties of the travelling reaction fronts, such as the wave speed and the burnt temperature are derived numerically over a range of different parameter values, such as those describing the relative enthalpies, rates and activation energies of the endothermic and exothermic reactions. Unique travelling wave solutions are shown to exist for each distinct combination of the parameter values. Stability analyses using both Evans function methods and direct numerical integration of the governing partial differential equations indicated that the travelling reaction front solutions are linearly stable if the heat release from the exothermic reaction is sufficiently large, otherwise the reaction fronts develop pulsations. In particular, using a finite-element package to numerically integrate the governing partial differential equations, period-1 and period-2 type oscillatory behaviour was observed prior to wave extinction. [ABSTRACT FROM PUBLISHER]