Effect of weed management practices and spacing on weed control


To study the effect of weed management practices on weed control in wheat, an experiment was conducted at two locations Such as Agricultural Research Farm, NWFP Agricultural University, Peshawar and Agricultural research Farm, Faculty of Agriculture, Gomal University, D.I.Khan for the year 1998-1999 and 1999-2000. The experiment was laid out in split-split plot Design with three replications. The factors included in the experiment were varieties (Bakhtawar-92, Ghaznavi-98, and Inqilab-91) being assigned to main plots, while herbicides such as broad-spectrum herbicide, (2.4-D 72EC + Isoproturon 75 WP @ 623 and 649 g a.i. ha-1, respectively), broad Leaf herbicide, (2,4-0 72 EC @ 711 g a.i. ha-1), grasses weeds herbicide, (Isoproturon 75 WP @ 968 g a.i. ha1), and weedy check (no herbicide) were kept in sub-plots.

Effect of weed management practices and spacing on weed control: agrinfobank.comThe row spacing (18, 25, and 32 cm) were allotted to sub-sub -plots. The experiment was planted on 31 October and 15 November in both years at Peshawar and D.I.Khan, respectively. Data were recorded on weed density and some agronomic, morphological and physiological traits of wheat and net profit and cost benefit ratio were calculated. The data for the individual trait were subjected to analysis of variance (ANOVA) and the means were separated by LSD. Variety Bakhtawar-92 was more productive and profitable than Ghaznavi-98 or Inqilab-91. It produced higher number of tillers m-2 (6% and 13%), grain yield (5% and 10%) and net profit (8% and 17%) than Ghaznavi-98 and Inqilab-91, respectively. The plots sown to Inqilab-91 variety, which is tallest and has vigorous early growth, had lesser number of grasses and broad leaf weeds than other verities. In Inqilab-9 I grasses weeds were reduced to 11% and 5%, and broad leaf weeds by 8 and 10% as compared to Bakhtawar-92 and Ghaznavi-98, respectively. The application of broad-spectrum herbicide consistently controlled both grasses and broad leaf weeds in all varieties at all row spacing in both locations and years. The increase in number of tillers m-2 (17%), number of productive tillers m-2 (18%), spikelets spike-1 (5%), 1000-grain weight (4%), biological yield (19%), grain yield (21%), straw yield (18%), harvest index (11%), and net profit (32%) over weedy check was due to application of broad spectrum herbicide, which controlled both grasses and broad leaf weeds. The interaction effect of broad- spectrum herbicides with variety Bakhtawar-92 produced significantly higher grain yield (24%) and net profit (34%), respectively. The interaction of broad spectrum with 18 cm row spacing was also significant in controlling both grasses and broad leaf weeds. The reduction in grasses and broad leaf weeds over the weedy check was 85 and 81%, respectively. The effect of 18 cm row spacing on reduction of both grasses and broad leaf weeds was significant, which ultimately increased number of tillers m-2 (9%), grain yield (10%) and net profit (23%), respectively over the weedy check. The 18 cm row spacing x Bakhtawar-92 interaction significantly increased grain yield (3% and 11 %) and net profit (8% and 23%) over 25 and 32 cm row spacing. In the light of the findings, it is suggested that for the integrated weed management in wheat, the broad-spectrum herbicide may be integrated with planting of aggressive varieties of wheat.


Soil Testing For Potassium And The Fertilizer Value Of Potassium Chloride Challenged By New Study

In the chemical age of agriculture that began in the 1960s, potassium chloride (KCl), the common salt often referred to as potash, is widely used as a major fertilizer in the Corn Belt without regard to the huge soil reserves that were once recognized for their fundamental importance to soil fertility. Three University of Illinois soil scientists have serious concerns with the current approach to potassium management that has been in place for the past five decades because their research has revealed that soil K testing is of no value for predicting soil K availability and that KCl fertilization seldom pays.

U of I researchers Saeed Khan, Richard Mulvaney, and Timothy Ellsworth are the authors of “The potassium paradox: Implications for soil fertility, crop production and human health,” which was posted on October 10th by Renewable Agriculture and Food Systems.Soil Testing For Potassium And The Fertilizer Value Of Potassium Chloride Challenged By New Study

A major finding came from a field study that involved four years of biweekly sampling for K testing with or without air-drying. Test values fluctuated drastically, did not differentiate soil K buildup from depletion, and increased even in the complete absence of K fertilization.

Explaining this increase, Khan pointed out that for a 200-bushel corn crop, “about 46 pounds of potassium is removed in the grain, whereas the residues return 180 pounds of potassium to the soil—three times more than the next corn crop needs and all readily available.”

Khan emphasized the overwhelming abundance of soil K, noting that soil test levels have increased over time where corn has been grown continuously since the Morrow Plots were established in 1876 at the University of Illinois. As he explained, “In 1955 the K test was 216 pounds per acre for the check plot where no potassium has ever been added. In 2005, it was 360.” Mulvaney noted that a similar trend has been seen throughout the world in numerous studies with soils under grain production.

Recognizing the inherent K-supplying power of Corn Belt soils and the critical role of crop residues in recycling K, the researchers wondered why producers have been led to believe that intensive use of KCl is a prerequisite for maximizing grain yield and quality. To better understand the economic value of this fertilizer, they undertook an extensive survey of more than 2,100 yield response trials, 774 of which were under grain production in North America. The results confirmed their suspicions because KCl was 93 percent ineffective for increasing grain yield. Instead of yield gain, the researchers found more instances of significant yield reduction.

The irony, according to Mulvaney, is that before 1960 there was very little usage of KCl fertilizer. He explained, “A hundred years ago, U of I researcher Cyril Hopkins saw little need for Illinois farmers to fertilize their fields with potassium,” Mulvaney said. “Hopkins promoted the Illinois System of Permanent Fertility, which relied on legume rotations, rock phosphate, and limestone. There was no potash in that system. He realized that Midwest soils are well supplied with K. And it’s still true of the more productive soils around the globe. Potassium is one of the most abundant elements in the earth’s crust and is more readily available than nitrogen, phosphorus, or sulfur. Farmers have been taught to think that fertilizers are the source of soil fertility—that the soil is basically an inert rooting medium that supports the plant.”

Khan and his colleagues pointed out that KCl fertilization has long been promoted as a prerequisite for high nutritional value for food and feed. To their surprise, they found that the qualitative effects were predominantly detrimental, based on a survey of more than 1,400 field trials reported in the scientific literature. As Khan explained, “Potassium depresses calcium and magnesium, which are beneficial minerals for any living system. This can lead to grass tetany or milk fever in livestock, but the problems don’t stop there.

Low-calcium diets can also trigger human diseases such as osteoporosis, rickets, and colon cancer. Another major health concern arises from the chloride in KCl, which mobilizes cadmium in the soil and promotes accumulation of this heavy metal in potato and cereal grain. This contaminates many common foods we eat—bread, potatoes, potato chips, French fries—and some we drink, such as beer. I’m reminded of a recent clinical study that links cadmium intake to an increased risk of breast cancer.”

While working in the northwestern part of Pakistan three decades ago, Khan was surprised to discover another use for KCl fertilizer. “I saw an elderly man making a mud wall from clay,” Khan said. “He was using the same bag of KCl that I was giving to farmers, but he was mixing it with the clay. I asked why he was using this fertilizer, and he explained that by adding potassium chloride, the clay becomes really tough like cement. He was using it to strengthen the mud wall.”

“The man’s understanding was far ahead of mine,” continued Khan, “and helped me to finally realize that KCl changes the soil’s physical properties. Civil engineers know this, too, and use KCl as a stabilizer to construct mud roads and foundations.” Mulvaney mentioned that he had demonstrated the cementing effect of KCl in his soil fertility class, and that calcium from liming has the opposite effect of softening the soil. He cautioned against the buildup philosophy that has been widely advocated for decades, noting that agronomic productivity can be adversely affected by collapsing clay, which reduces the soil’s capacity to store nutrients and water and also restricts rooting.

Khan and Mulvaney see no value in soil testing for exchangeable K and instead recommend that producers periodically carry out their own strip trials to evaluate whether K fertilization is needed. Based on published research cited in their paper, they prefer the use of potassium sulfate, not KCl.

Source: University of Illinois College of Agricultural, Consumer and Environmental Sciences