Modelling seed dormancy, germination and emergence of Striga hermonthica

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Water Management for Sustainable Irrigation in Rice (<i>Oryza sativa</i> L.) Production: A Review

In the face of the negative impacts of climate change and the accelerated growth of the global population, precision irrigation is important to conserve water resources, improve rice productivity and promote overall efficient rice cultivation, as rice is a rather water-intensive crop than other crops. For several decades, various water conserving technologies have been studied in order to significantly increase water use efficiency (WUE). The objective of this paper is to review the main technologies and approaches for assessing the water requirements of rice crop in order to contribute to water saving in irrigated rice production, after clarifying the performance indicators of the irrigated systems. Several scientific articles from previous studies were consulted and analyzed. These studies showed that irrigation water conservation includes a wide range of practices, staring from the crop irrigation water requirements assessment to the implementation of the water saving practices on the field. In addition, irrigation water conservation technologies could be categorized into three groups, namely water-conserving irrigation systems, water-saving irrigation methods, and water-conserving agronomic practices. The influence of the individual and combined irrigation water use efficiency tools was highlighted. This paper will enable researchers to acquire knowledge on water-saving methods for estimating the rice crop water requirements and thus allow them to effectively contribute to improve the performance of irrigated rice cultivation systems using various water conservation technologies

Water and nutrient use efficiency of soilless grown greenhouse tomato (Lycopersicon esculentum L.)

AbstractFertigation by drip irrigation enhances the supply of water and nutrients directly to the root zone of plants. This results in maximal crop water and nutrient uptake and reduces leaching of nutrients and chemicals from the root zone. Two tomato varieties were cultivated in soilless medium in two greenhouse conditions to assess fertilizer rate, and irrigation regime on yield, water and nutrient utilization under a factorial experimental layout in a split-split plot design. The treatments were: three levels of fertilizer rate (F1: 100%, F2: 80%, F3: 60%) as recommended for soilless grown greenhouse tomato production, three levels of irrigation regime (I1: 100%, I2: 80%, I3: 60%) with respect to the crop water requirement and two tomato genotypes (V1: Jalila F1, V2: Yetty F1). A 20% to 40% decrease in fertilizer rate and irrigation regime decreased cluster (0.9–6.6%), flower (0.9–13.1%) and fruit (0.3–15%) formation under greenhouse condition. Marketable yield as affected by the combination of fertilizer rate by irrigation regime by genotype increased with increase in crop water productivity and nutrient use efficiency under greenhouse condition. Nutrient use efficiency increased with increase in crop water productivity. Evidently, marketable yield, crop water productivity and nutrient use efficiency vary significantly with plant nutrition, irrigation, genotype and its interactions. These are critical in curbing water scarcity, managing the economic crisis and to further the quest for zero hunger

Modelling effects of prolonged conditioning on dormancy and germination of Striga hermonthica

The impact of environment on the germination biology of the parasite was studied in the laboratory with seeds conditioned at various water potentials, urea concentrations and at 17.5 to 37.5°C for up to 133 days. Maximum germination was observed at 20 to 25°C. Water stress and urea suppressed maximum germination. The final percentage germination response to period of conditioning showed a non-linear relationship and suggests the release of seeds from dormancy during the initial period and later on dormancy induction. Germination percentage increased with increase in conditioning period to a threshold and remained stable for variable periods followed by a decline with further extension of conditioning time. The decline in germination finally terminated in zero germination in most treatments before the end of experimentation. The investigated factors of temperature, water potential and urea showed clear effects on the expression of dormancy pattern of the parasite. The effects of water potential and urea were viewed as modifying a primary response of seeds to temperature during conditioning. The changes in germinability potential during conditioning were consistent with the hypothesis that dormancy periods are normally distributed within seed populations and that loss of primary dormancy precedes induction of secondary dormancy. Hence an additive mathematical model of loss of primary dormancy and induction of secondary as affected by environment was developed as: G = {[Φ-1 (Kp+ (po+pnN+pwW) (T-Tb) t)]-[Φ-1 (Ks+ ((swW+sa)+sorT)t)]}[Φ-1(aT2+bT+c+cwW)]