Potato Review

www.potatoreview.com POTATO REVIEW MAY/JUNE 2023 17 FERTILISATION Phosphite boosts early marketable yield Fens grower who has been ne-tuning fertiliser application for six years tells Potato Review how he has perfected his method. B IOSTIMULANTS applied to potatoes at the pre tuber initiation stage have enabled a Cambridgeshire grower to tap into the early market that supplies sh and chip shops. Having access to the early potato market has paid dividends for L and AE Munns of Westmoor Farm near Chatteris. e 40ha grown predominantly for customers around East Anglia, command a healthy premium over the same crop lifted only two weeks later. e grade one fen soils support a rotation based on wheat, sugar beet, barley and potatoes. Potatoes are sold directly o the eld. ere is no cold or ambient storage. Harvest starts at the end of August and is nished by the end of September. On a good day grower George Munns can lift up to 70t graded and weighed o the eld, with a Grimme Allrounder bought in 1989 and pulled by a MF 6180. e potatoes are graded and packed into 25kg bags and transported in 8t lots by trailer to the eld edge or back to the yard. Seed grade is also graded out into a hopper. A sample is sent to NIAB and if it is suitable quality, he will store it in a local cold store for the following season. Early saleable crop yields regularly exceed 15t/ha with a price tag often more than £250/t, compared to perhaps only £150t/ ha for the same crop only two weeks later. “Targeting the early potato market is the key and concentrating on getting the crop o to a good start is critical if margins are to be maximised. Providing the correct nutrition and applying it at the pre-tuber initiation phase is critical,” said George. Maximising yields and achieving high quality is mostly about nutrition he says. Standard nutritional packages will give his potatoes a good start but the attention to detail helps to produce a uniform and quality crop, George said. For the past six years George has ne-tuned his fertiliser inputs. While researching the bene ts of foliar phosphite, he consulted biostimulants and foliar nutrition supplier Ilex Envirosciences. Sales Director John Allen provided technical advice on the bene ts of phosphite as a source of phosphorous as opposed to the standard phosphate that is available in many fertiliser programmes. Foliar phosphite in the form of PK Maxx Plus is now applied routinely, which George says has made a signi cant impact on yield and quality. A key bene t of has been enhanced root development, which helps the crop forage for essential nutrients and minerals. It is also claimed that up take-up of this essential nutrient is quicker than when it is applied in a phosphate form. Adding a phosphite source early de nitely brings the harvest date forward without putting the crop under stress, according to George. A stressed crop stops growing so the early application of phosphite helps maximise yields at the start of the lifting season. Grading in the eld only means George’s aim is to produce a regular sample of 50mm + tubers as early as possible in the season. Smalls are graded out and can be retained for seed for the following year. “Planting early brings the sample forward, but this can stress the crop, which makes the correct nutrition at this time essential as well as making available plenty of water through irrigation,” he said. “ e minute we have a good sample, we start harvesting. e PK Maxx Plus has de nitely enhanced the rooting. e key is to apply it alongside our standard fertiliser programme.” PK Maxx Plus is applied at a rate of 1l/ha during the pre-tuber initiation stage, which is when the plant is weaning o the mother tuber, followed by a second application at 2l/ha at tuber initiation. ereafter each blight spray up until owering will include a further 1l/ha of this phosphite source. “Potatoes inherently have poor root systems, but we have de nitely found that the product improves root bres. We have also found that when the product is applied at 1l/ha alongside each blight spray - when there is a target leaf area - we think it supports a better blight control,” said George. e business only grows Sagitta, which is popular with the sh and chip trade because of its attractive bright skin, uniform shape and consistent high frying quality. For growers, it is a multi-purpose, reliable yielder, and an early maturing and tuberisation variety. But it can su er from poor rooting, especially on the more peaty soils in the area. Early applications (pre-tuberisation) de nitely increase the root mass, according to George. Early lifting impacts canopy density and although George says that in a good year he gets canopy closure, it is more the exception than the rule, so it is important to get the foliar phosphite on as early as possible, ideally before tuber initiation, to maximise rapid growth and early development of the crop. “On our black fen soils, we always get a manganese de ciency too, so the PK Maxx Plus goes on at the same time as the manganese foliar spray. Manganese de ciency causes a paling of the leaf and it normally occurs in patches across a eld. Visually the condition should not be mistaken for nitrogen de ciency,” said George. “ e application of PK Maxx Plus including manganese de nitely helps to get manganese into the crop more e ciently. “Interestingly, often at the point of lifting, the price we get per acre is the same as the price we get later in the season when the yields increase and the price drops. is is a simple supply and demand equation, but it demonstrates that the key to maximising pro tability is to get the crop o early and to have a regular sample as soon as possible. “With potato prices normally dropping as the supply increases, the PK Maxx Plus inclusion gives me the piece of mind and con dence to target the early marketable yield. e length of time that we harvest is where we make our biggest gain. We work to be nished lifting before everyone else starts,” he said. George Munns