Search

Processing-tomato (Lycopersicon esculentum L.) cultivation in California has transitioned to the use of transplants, subsurface drip irrigation (SDI), and shallow tillage from direct-seeded, flood-...

Nepal ranks 49th in the world for biodiversity richness. Among 577 cultivated species in Nepal, 484 are indigenous and 93 are introduced. About 85% of these cultivated crop species are neglected an...

Biological invasions in established cropping systems impact biodiversity and agricultural sustainability. Under conditions of multi-year drought and elevated tropospheric ozone (O3), several Amaranthus species have recently become problematic weeds in California. We examined responses of common waterhemp (A. tuberculatus) to 12-h mean O3 exposures of 4, 59, or 114 nmol O3 mol air−1, with two levels of irrigation, 33% (deficit irrigation, DI) or 100% (well-watered, WW) of field capacity. Daytime stomatal conductance (gs) was reduced by O3 but not by DI. Nocturnal gs was uncommonly large but unaffected by either treatment. Plant productivity was not affected by O3 or DI. Leaf mass per unit area and root mass per unit leaf area were reduced by O3 but not by DI. Tolerance of this species to O3 and deficit irrigation may increase its competitiveness with crops. High night-time water loss may reduce water availability for competing crops. The competitiveness of common waterhemp may increase, as climate ...

Weed management in Romaine lettuce (Lactuca sativa L. var. longifolia) is an economic challenge for organic farmers. This study evaluated the effect of weed-free durations on crop yield and quality...

Sorghum [Sorghum bicolor (L.) Moench] is being explored in California as a multi-utility, water-use efficient crop, but water and salt stresses are common in the state’s San Joaquin Valley (SJV). Experiments were conducted to study the effect of water and salt stress on seed germination and the effect of salt stress on the early growth of a forage (SS405) and a grain (NK5418) sorghum hybrid. Solutions ranging from 0 to −5.56 MPa and 0 to 25 ds m−1 were prepared using polyethylene glycol and sodium chloride, respectively, and germination was evaluated in these solutions. Salinity tolerance at early growth stage was tested on plants irrigated with solutions ranging from 0 to 20 ds m−1. Plants were harvested 6 weeks after planting and their aboveground biomass was recorded. Chlorophyll content and stomatal conductance were also measured. Germination was reduced by 50% in SS405 and NK5418 at −2.5 MPa and −1.5 MPa, respectively, and by 50% in SS405 at 19.3 dS m−1, but NK5418 had 70% germination even at...

Chemical defoliation is a necessary pre-harvest practice in Pima cotton (Gossypium barbadense L.) production in California. Growers begin defoliating as early as possible but yield and quality loss can occur if the bolls are not fully mature. Harvest aids can advance harvest dates, avoid late-season pests, and adverse weather conditions in California. A study was conducted on Pima cotton, cv. ‘Phytogen-802’. Different rates of Ginstar (ai thidiazuron/diuron, Bayer CropScience) or Ginstar plus Finish 6-Pro (ai ethephon/cyclanilide, Bayer CropScience) were applied at 6 to 7 nodes above cracked boll (NACB) or 4 to 5 NACB at various rates. Results showed that these harvest aids could be applied at the tested rates at both timings without any adverse effects on percent open bolls, and lint yield and quality. Therefore, application of these harvest-aid materials starting at 6 to 7 NACB can benefit Pima cotton growers in California as early harvests can be achieved without compromising lint yield or quality.

Onion (Allium cepa) production in California’s San Joaquin Valley (SJV) typically involves intensive tillage and sprinklers for crop establishment followed by drip irrigation (DR). Studies were conducted at Five Points, California, in 2011 and 2013 to compare minimum tillage (MT) practices under overhead irrigation (OH) and DR relative to crop growth, yield, and costs. The experimental design was a randomized complete block with four replications of each irrigation treatment. Crop growth in both systems was similar; however, there was a year X irrigation system interaction for crop yields. In 2011, yields were not affected by irrigation, but in 2013, irrigation type affected yield with the OH system having 15.4 t/ha higher production than the DR system (78.6 t/ha vs. 63.4 t/ha). Onion size was not affected by irrigation system. Cost estimates indicated that onion production could be $564 per hectare lower with the OH system compared with the DR system, if yields were maintained. Because of cost savings fr...

Conservation cropping systems are being developed for cotton (Gossypium spp.) traditionally grown on raised beds with several soil-disturbing tillage passes in the San Joaquin Valley (SJV) of California, USA. Overhead (OH) irrigation and subsurface drip irrigation (SSDI) systems are water-conserving techniques being tested with reduced tillage in the SJV. However, crop growth, yield, microclimate, and pest population dynamics in these systems have not been documented. A field study was conducted in 2011 and 2012 at Five Points, Calif., to evaluate the difference between the two irrigation systems. Cotton cv. Phytogen 725 RF was no-till planted into wheat residue. In both years, the soil surfaces in the OH plots were 1° to 2°C cooler and 5% to 15% wetter than the SSDI plots. These differences had no effect on crop growth, development, yield, or quality, but weed densities and biomass were lower in the SSDI than in the OH in both years. However, the SSDI plots had more spider mites (Tetranychus sp.) than th...

Summary Agroecology is emerging from the conceptual realm to become a significant discipline in North America and many parts of the world. We explore 10 dimensions of agroecology that are important in developing a more biologically-based science of agriculture: (1) a new philosophy of agriculture, (2) systems thinking, (3) local adaptation, (4) the non-crop biota, (5) crop autecology, (6) encompassing the agricultural landscape, (7) closing the materials cycle: crops, livestock and local or global cycling, (8) technology and ecology, (9) human ecology, and (10) the natural dimension. Agroecology deals with the applications of ecological principles in agroecosystems and it represents a logical response to shortcomings of conventional agriculture. Current crop production approaches fail to account for biological complexities of agro-ecosytems and the need to feed the world without jeopardizing the sustainability of its life support systems. A key strategy employed by agroecologists is to compare agroecosyst...