Roger Nkoa Ondoua

• PhD
• Professor (Assistant) at Montana State University

The use of grains from row crops to produce bioethanol or biodiesels has had a negative impact on food prices. At the same time, systematic and complete removal of crop residues for biofuel production adversely impacts soil quality. This article discusses the seven-year change in some of the soil chemical properties that affect soil quality, follow...

Most agronomic studies have focused on increasing nitrogen use efficiency (NUE) through the management of nutrients in the soil (4Rs), but little is known about the effect of cropping systems on NUE. This study examines the differences in NUE among five popular spring wheat varieties as related to soil N fertility and two Montana cropping systems,...

The annual global economic loss caused by weeds has been estimated at more than $100 billion U.S. dollars (Appleby et al. 2000). Additionally, worldwide annual herbicide sales are in the range of U.S. $25 billion (Agrow 2003). In light of these large dollar figures, it becomes clear that a greater understanding of crop—weed interactions is essentia...

Understanding abundance and distribution of weed species within the landscape of an agroecosystem is an important goal for weed science. Abundance is a measure of the number or frequency of individuals in an area. Distribution is a measure of the geographical range of a weed species. The study of weed population's abundance and distribution is help...

Knowledge on the interaction between plants and organic amendments is critical for the basic understanding of agroecosystems sustainability. Organic amendments are of great interest in agriculture by virtue of their ability to restore lost soil organic carbon in eroded or conventionally cultivated soils. The major objective of this study was to dem...

In light of frequent price hikes of imported fuels and the everlasting growth in the world's crude oil consumption, producing energy from renewable, non-fossil sources, such as crop residues and dedicated energy crops, has gained an unprecedented attraction across developed countries. This study aimed at assessing the dynamics of crop residues biom...

Knowledge on the interaction between plants and organic amendments is critical for the basic understanding of agroecosystems sustainability. Organic amendments are of great interest in agriculture by virtue of their ability to restore lost soil organic carbon in eroded or conventionally cultivated soils. The major objective of this study was to dem...

Intensive soil fertilization with mineral fertilizers has led to several issues such as high cost, nitrate pollution and loss of soil carbon. Fertilization with organic matter such as compost therefore represents an alternative for sustainable agriculture. Traditional organic amendments such as manures, composts and sewage sludge have been extensiv...

Determination of crop nitrogen requirement is at the basis of crop nitrogen fertilizer recommendation. This study aimed at determining the nitrogen demand of broccoli plants (Brassica oleracea var. italica). A mathematical model predicting nitrogen demand was developed and successively tested in an experiment involving a broccoli cultivar at four s...

Summary • Purified enzymes are known to exhibit either noncooperative or cooperative kinetics, with respect to their substrates. In all cases, enzyme activity increases with substrate concentration up to saturation. Here, we report a different kinetic pattern of a regulated enzyme: reciprocal cooperativity. • Broccoli plants (Brassica oleracea var....

Current practice for greenhouse broccoli production is to fertigate with N at a constant rate. Because crop N demands differ according to growth stage, constant N fertilisation under- or over-supplies N at some stages. Nitrogen phasing, whereby successive, different levels of nitrogen are applied, was examined in the two broccoli cultivars Arcadia...

A greenhouse experiment on broccoli (Brassica oleracea var. italica, cvs Windsor and Arcadia) was carried out in order to demonstrate that supplying nitrogen (N) to meet the nitrogen demands of plant growth stages, through N phasing, improves plant growth and yield, as compared to fertilizing at the conventional, optimal, constant N rate. Two brocc...